The perspectives of successful ageing among older adults aged 75+: a systematic review with a narrative synthesis of mixed studies

Abstract Older adults 75 and above are a fast-growing segment of the population. However, few studies have investigated what it means to age successfully from their perspective. This group of older adults face challenges that might characteristically differ from younger older adults. Therefore, the aim of this study was to conduct a systematic review of the perspectives of older adults aged 75 and above regarding what it means to age successfully and to summarise the findings through a narrative synthesis. We also aimed to provide a snapshot of inhibitors and facilitators to achieve successful ageing. A systematic review of the 75+ older adults’ perspectives was conducted across PubMed, CINAHL, Scopus, Web of Science and PsycINFO. Qualitative, quantitative and mixed-methods original peer-reviewed studies were included. After reviewing 4,661 articles, 15 articles met the inclusion criteria and 15 themes were identified. They ranged from biomedical components such as physical functioning to psychosocial components such as relationships, reflections on life and past experiences, preparations for death and environmental factors. The findings revealed that as people age, their definition of successful ageing changes, expanding the current conceptualisation of successful ageing by including additional factors that can act as facilitators and/or inhibitors, such as death and environmental factors. The findings also highlight the need for further research on theory development by considering age-related differences and the perspectives of under-studied populations.


Introduction
The last century has witnessed a notable increase in life expectancy in high-income countries such as the United States of America, Canada, Australia, Japan and Western European countries.If this development persists throughout the present century, it is expected that most babies born in 2000 will live to 100 (Christensen et al., 2009).Those life expectancy projections solicit theoretical and empirical attention to understanding of successful ageing and ways to achieve it.
Although the successful ageing model dates back to 1961, when Havighurst (1961) introduced the term, the model only gained popularity first when Rowe and Kahn (1987) distinguished between 'usual' and 'successful ageing'.The latter was eventually defined in terms of avoiding diseases and disability, maintaining cognitive and physical functioning, and being engaged with life (Rowe and Kahn, 1997), and became a primarily a prominent biomedical model of successful ageing.Psychosocial models of successful ageing emphasise independence, life satisfaction, social engagement, personal growth, adaptability, self-worth, autonomy and social participation (Bowling and Dieppe, 2005), two of which are well known as Selective, Optimisation and Compensation (SOC; Baltes and Baltes, 1990) and the Socio-emotional Selectivity Theory (SST; Carstensen, 1992).
Successful ageing has different interpretations and has been used interchangeably with terms such as ageing well, active ageing, positive ageing, optimal ageing, healthy ageing and robust ageing (Nusselder and Peeters, 2006;Hung et al., 2010;Cosco et al., 2013;Katz and Calasanti, 2015;Martin et al., 2015), however, it remains unclear what successful ageing is, how it can be measured and how to best achieve it (Strawbridge et al., 2002;Depp and Jeste, 2006).The theoretical successful ageing models have been criticised for paying insufficient attention to the voices of older people, for failing to capture the subjective views of successful ageing from diverse cultural perspectives, for being too narrow to be of use for public health purposes, for being too exclusive and for marginalising those who are not ageing successfully (Martinson and Berridge, 2015).A few studies have investigated lay views on successful ageing but to a lesser extent than theory-driven definitions (Phelan et al., 2004;Bowling and Dieppe, 2005;Jopp et al., 2015), which has created a gap between theoretical and lay definitions of successful ageing.
It has been suggested that a successful ageing model for all age groups, backgrounds and cultures is not feasible (Martinson and Berridge, 2015), especially since the perception and experience of older age has been shown to be influenced by cultures, individual experiences and societal expectations (Löckenhoff et al., 2009;Martin et al., 2015).Additionally, most literature reflects Western perceptions of ageing that define success in terms of individual accomplishments (Torres, 1999;Kendig, 2004).Nevertheless, Rowe and Kahn's (1997) definition of successful ageing remains the most widely used, even though it is unrealistic for most people to be disease-free in old age (Bowling and Dieppe, 2005), especially after the age of 75 (Jaul and Barron, 2017), thus making it harder to attain Rowe and Kahn's criteria for successful ageing (Katz and Calasanti, 2015).This specific age group has not been the target of previous reviews (Hung et al., 2010;Cosco et al., 2013;Teater and Chonody, 2019) on the meanings and definitions they attribute to successful ageing, as such reviews have not differentiated between age groups and methodologies, which contributes to the homogenisation of older adults.This is problematic since age-related physiological consequences such as frailty, falls, depression, diseases, sensory loss and disability are more often experienced by the older age groups (Lennartsson and Heimerson, 2012;Jaul and Barron, 2017).Moreover, older adults report more age-related discrimination and stereotyping which can affect their self-perceptions of ageing and successful ageing (Giasson et al., 2017).Considering current life expectancy developments in most countries, new definitions of older people could be re-examined and re-classified (Ouchi et al., 2017).Thus, the present study aimed to review systematically the perspectives of successful ageing from the viewpoint of 75+ older adults, as reported in qualitative, quantitative and mixed-design research, and the factors that facilitate or hinder one's ability to age successfully.

Search strategy
The search strategy was developed, and the search was conducted in collaboration with an experienced medical librarian (see Table S1 in the online supplementary material).The search strategy was based on keywords and MeSH (Medical Subject Headings) terms adapted to suit each database, following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA; Moher et al., 2009).The systematic review protocol was registered in PROSPERO (No. CRD42019140994).
PubMed, Web of Science, CINAHL, PsycINFO and Scopus online databases were searched between October and December 2018 and updated on 18 January 2020.All peer-reviewed articles published before January 2020 were eligible for inclusion.The following search terms were used: (a) successful ageing or synonyms of the concept such as optimal ageing, ageing well, positive ageing, healthy ageing and active ageing (used with both American and British English spellings); and (b) perception or view, definition, attitude, self-rated, opinion and interpretation, in both singular and plural forms.Subsequently, these terms were combined into (a) and (b).All fields, MeSH terms and wild card symbols were used to ensure all keyword variations.The process was repeated across all the databases.

Inclusion and exclusion criteria
After removing duplicates, two of the authors (ACB and EMT) independently screened the titles and abstracts to identify relevant articles for full-text extraction.Through the snowballing method, references of relevant articles were manually screened to ensure that all relevant articles were found.Any disagreements regarding the inclusion of studies were resolved by discussion.We included: (1) Original qualitative, quantitative and mixed-methods peer-reviewed journal articles focusing on the lay views of older people aged 75 and above.(2) Studies involving age groups 60 years and above, only if a separate analysis on the views of older people aged 75 and above was reported.
Additionally, we excluded: (1) Non-peer reviewed articles such as book chapters, dissertations, review articles, opinion papers, and clinical or intervention studies.(2) Studies without a distinct interpretation of the views of older adults aged 75 and above.

Data extraction
The authors extracted data on a standardised form developed for this review.

Data analysis and synthesis
As the articles identified were mostly qualitative and comparable, data were analysed through a narrative synthesis using thematic analysis (Popay et al., 2006); Snilstveit et al., 2012).Themes of successful ageing created by study authors and direct quotes from study participants from the reviewed studies were identified, extracted, coded and analysed, using Microsoft Word and NVivo 12 (QSR International, Melbourne).If the themes were clearly stated, they were extracted as they were; otherwise, two of the authors (ACB and HH) generated new themes inductively (Braun and Clarke, 2006) based on the explanations provided by the authors of the particular study.Two researchers (ACB and HH) worked on the data extraction and thematisation, which consisted of grouping sub-themes into overarching themes.Our synthesis involved integrating and aggregating findings from multiple studies into new broader themes.Disagreements were resolved through regular meetings and deliberations.

Assessment of methodological quality
A quality appraisal of included studies was conducted independently by two of the authors (ACB and HH) and checked by the last author (EMT).All the studies were quality-appraised using the Mixed Methods Appraisal Tool (MMAT) version 2018 (Hong et al., 2018) which has been designed to assess multiple types of study designs, including mixed-methods, quantitative and qualitative studies.There are five scoring items with answers of 'yes', 'no' and 'cannot tell', and a comments section for reviewers' explanations.The current study aims to provide a comprehensive synthesis of the lay views of successful ageing among older adults aged 75 and above.Due to the limited number of articles conducted in the field the subject matter (the lay views of successful ageing) was considered more important than the quality of the study's methodology.Thus, no studies were excluded based on methodological quality.However, if we had identified inadequately reported studies, we would have excluded them from the analysis.The details of the quality appraisal of the individual studies are provided in Table S2 in the online supplementary material.

Study selection and characteristics
The literature search identified 11,356 articles published until January 2020, as presented in Figure 1.After duplicates had been removed, the titles and abstracts of 4,661 articles were assessed for eligibility, based on the inclusion and exclusion criteria.The title and abstract screening resulted in 309 articles for full-text reading.
By applying the exclusion criteria, 294 articles were excluded after the full-text screening: 104 articles were excluded based on age, nine because they were reviews, 126 as they did not look at successful ageing from the lay views, 43 because they were non-peer-reviewed papers (reports, editorials, book chapters) and 12 as the full text was not found (Figure 1).Thus, 15 articles published between 2001 and 2019 with sample sizes varying between six and 1,745 were included.Most of the participants in these studies were male, accounting for 56.5 per cent of the total population sample, as shown in Table 1.The included studies mostly covered high-income countries.

Findings
Upon completing the thematic analysis, we identified 15 themes of successful ageing across the 15 articles included in this review.Each theme comprises factors that can act as facilitators and/or as inhibitors to successful ageing.We found that facilitating factors were most reported in all the themes (see Tables 2 and 3).
Several facilitators were reported in each theme, ranging from six to 19 (in themes 1 and 3) and inhibitors between none (theme 7, 9, 11 and 13) to nine (theme 3).The identified 15 themes consisted of aggregates of factors extracted from the 15 articles.

Theme 1: Acceptance
This theme was found in eight articles.Acceptance is understood as 'the mental recognition that personal circumstances change over time, and that one has accepted and come to terms with these changes' (Tate et al., 2013).The importance of accepting the realities of ageing was noted (Dionigi et al., 2011;Collis and Waterfield, 2015;Chen et al., 2019).This includes accepting the pain and physical limitations that come with age (Horder et al., 2013;Tate et al., 2013;Collis and Waterfield, 2015;Sato-Komata et al., 2015;Carr and Weir, 2017), as well as cognitive declines (Sato-Komata et al., 2015).It also extended to accepting current phases of life, situations and abilities (Horder et al., 2013;Carr and Weir, 2017) and anticipating change (von Faber et al., 2001).Acceptance was related to uncontrollable events such as death (Horder et al., 2013;Sato-Komata et al., 2015) and illness of friends and relatives (Horder et al., 2013).Adaptation and continuity were closely related and were reported in eight articles.Adaptation was defined in terms of adapting to the changes that occur in the process of ageing (von Faber et al., 2001;Horder et al., 2013).This includes the use of assistive devices (Tate et al., 2013), living one day at a time, moderation, planning for future support (Tate et al., 2013), keeping going (perseverance) (Dionigi et al., 2011) and receiving support when needed (Tate et al., 2013).In other studies, adaptation also meant people doing things despite being in pain, refraining from doing things they did before due to the risk of falling (Collis and Waterfield, 2015), and dealing with personal stressors and overwhelming emotions (von Faber et al., 2001;Tate et al., 2013).Moreover, strategies to deal with an increased vulnerability in relation to one's own body and one's immediate surroundings were also mentioned (Horder et al., 2013).Continuity meant continuing to work towards a goal (Dionigi et al., 2011), persevering despite pain (Collis and Waterfield, 2015), retaining good elements of ageing until death (Nosraty et al., 2015) and simply remaining the same (Torres and Hammarstrom, 2009).
Finally, some authors reported conflicts over declining functions and denying difficulties (Nosraty et al., 2015;Sato-Komata et al., 2015).These included the       sensation of loss of physical and cognitive functions, fear of one's inability to predict future declines, the acceptance or denial of health conditions, the need to feel self-assured of one's health condition and the realisation of having aged (Sato-Komata et al., 2015).
Theme 3: Attitudes, positivity and happiness Thirteen studies mentioned attitudes, both positive and negative, as a component of successful ageing.In terms of positive attitudes, studies reported satisfaction with life (Bowling, 2006;Dionigi et al., 2011;Nosraty et al., 2015), gratitude (von Faber et al., 2001;Horder et al., 2013;Tate et al., 2013;Sato-Komata et al., 2015), as well as being curious about learning new things and forgiveness (Torres and Hammarstrom, 2009).In the same vein of positivity and happiness, a positive approach to life (Bassett et al., 2007;Torres and Hammarstrom, 2009;Tate et al., 2013), happiness about growing older (Collis and Waterfield, 2015), a happy outlook (Tate et al., 2013), a good mind-set (Bowling, 2006;Bassett et al., 2007;Lee et al., 2017) and enjoyment of life (Bowling, 2006) were reported.This positive approach is occasionally paralleled by a denial of difficulties and avoiding nagging (Torres and Hammarstrom, 2009;Collis and Waterfield, 2015).Other studies mentioned the importance of remaining positive despite disability, diseases, physical decline and negative life events (Collis and Waterfield, 2015;McGrath et al., 2016;Carr and Weir, 2017).Combating these negative life events with positive humour was deemed a good strategy (McGrath et al., 2016).Negative attitudes were also reported.Some studies mentioned negative attitudes and pessimism (Collis and Waterfield, 2015;McGrath et al., 2016;Chen et al., 2019) in the presence of illness, pain, the loss of a loved one and due to past life experiences (Nosraty et al., 2015).These life events mitigate against successful ageing (Collis and Waterfield, 2015).Others mentioned hiding negative feelings from others to avoid being perceived as complainers, an old-age stereotype.Moreover, one study mentioned the feelings of fear, anger and frustration to maintain a false sense of happiness to loved ones and care staff (Collis and Waterfield, 2015).

Theme 4: Environmental factors and system influences
This theme was reported in nine articles.The environmental context in the presence of disability (McGrath et al., 2016) and the living circumstances (Bowling, 2006;Nosraty et al., 2015) were mentioned as important determinants to successful ageing.These could enhance opportunities and safety but also could be hindering in nature (Horder et al., 2013).In some studies, home-ownership, adequate accommodation and access to good housing for seniors were considered important (Bassett et al., 2007;Horder et al., 2013;Nosraty et al., 2015).While some people wanted to stay in their own home as long as possible, others believed that moving to a seniors' residence provides security: 'Well, the first condition is to stay fit enough to be able to live on your own.And to live at home; I'd much rather live here at home than in some institution … (5, male, living alone, receiving daily home help)' (Nosraty et al., 2015, p. 54).Apart from living arrangements, a favourable outdoor environment was reported (Bassett et al., 2007;Horder et al., 2013), which included weather  (Horder et al., 2013;McGrath et al., 2016), season, time of day and lighting (McGrath et al., 2016).However, ice and snow in winter can become a threat to successful ageing as they impede people from staying active (Horder et al., 2013).System influences included health care (Bassett et al., 2007;Horder et al., 2013;Tate et al., 2013;Collis and Waterfield, 2015) and social support systems (Bassett et al., 2007).These comprised health-care providers (Tate et al., 2013), medication (Bassett et al., 2007;Tate et al., 2013;Collis and Waterfield, 2015), receiving medical treatment (Bassett et al., 2007;Sato-Komata et al., 2015), going for regular medical check-ups (Sato-Komata et al., 2015;Chen et al., 2019) and receiving informal care (Bassett et al., 2007).Advances in science and medical knowledge, the dissemination of medical research and increased availability of health-care services (Bassett et al., 2007) were also seen as determinants of successful ageing.
Older adults expected that health care would attend to their medical needs (Bassett et al., 2007;Horder et al., 2013;Tate et al., 2013;Nosraty et al., 2015;Sato-Komata et al., 2015).Additionally, awareness and information by the healthcare systems about older adults' medical conditions contributed to the feelings of security and health (Horder et al., 2013).In cases of disability, participants reported valuing compliance with the requirements of the care staff.These included refraining from travelling alone and using the stove, and only using taxis for transportation (McGrath et al., 2016).
While the importance of health care was noted, some participants felt neglected by the health-care systems through a lack of advice on the premise that their pain was a natural result of ageing (Collis and Waterfield, 2015).Some others felt frustrated that their condition did not improve, despite regular visits to the hospital (Sato-Komata et al., 2015), and with lack of treatment options (Collis and Waterfield, 2015).Others reported that they were prescribed pills instead of receiving advice: 'I don't know if you are given a lot of advice now, apart from … given tablets … I think you used to get more advice' (Collis and Waterfield, 2015, p. 24).In general, the shortcomings of informal support systems were noted: 'A sense of caring for seniors is absent in our community today' (Bassett et al., 2007, p. 123).
Theme 5: Financial resources Eight studies included the theme of financial resources.Financial resources were needed to buy essentials (Bowling, 2006;Bassett et al., 2007;Torres and Hammarstrom, 2009;Horder et al., 2013;Nosraty et al., 2015;Sato-Komata et al., 2015;Chen et al., 2019), pay bills (Bowling, 2006;Horder et al., 2013) and retain autonomy in financial decisions (Nosraty et al., 2015;Chen et al., 2019) -'Money doesn't buy happiness, but it helps to buy the support you need to live well' (Bassett et al., 2007, p. 122).Financial resources were discussed in the context of having a sufficient pension, as stated by a Finnish female: 'Well, health of course and then sufficient income.I mean that your pension is enough to cover all medical costs and the like' (Nosraty et al., 2015, p. 54).Besides making ends meet, financial planning (Bassett et al., 2007;Horder et al., 2013;Carr and Weir, 2017;Chen et al., 2019), budgeting, investing, being debt-free and good financial management were also reported as determinants of successful ageing (Bassett et al., 2007).Financial concerns about the future, and hence worries about savings (Sato-Komata et al., 2015), were also reported, as savings were seen as a way to ensure financial security in case of major illness (Chen et al., 2019).
For some, health meant the absence of diseases and limitations (Bowling, 2006;Horder et al., 2013;Tate et al., 2013).For others, health was seen as a resource for being active and participating on a personally desired level, despite the presence of disease and disabilities (Knight and Ricciardelli, 2003;Horder et al., 2013).Not surprisingly, some participants valued their personal health almost as much as they valued the health of friends and family (Horder et al., 2013).Partners' or relatives' ill-health was seen as a reason for sadness and worries.The dependency on immediate relatives' health, with partner care-giving, was seen as a barrier to engaging in activities and a threat to personal freedom, but a spouse's death was seen as an even bigger threat (Horder et al., 2013).Additionally, some considered a degree of morbidity to be part of the natural ageing process (Horder et al., 2013;Nosraty et al., 2015;Sato-Komata et al., 2015).
Theme 9: Reflections on life and past experiences Seven studies mentioned this theme.This included reflections on life and past experiences (Sato-Komata et al., 2015).In this theme, reflecting on life (Sato-Komata et al., 2015) also included anticipating the future even in very old age (Nosraty et al., 2015), which even extends beyond death (von Faber et al., 2001).In some studies, living a joyful long life (Bowling, 2006), even longer than others (Tate et al., 2013), also seemed to be important.Certain life experiences were associated with successful ageing, such as education and career, being retired and having served in the Second World War (Tate et al., 2013).Looking back to past experiences generated some nostalgia among participants who thought 'things were better in the past' (Sato-Komata et al., 2015).
Retrospection has its share of regrets and focus on losses (Horder et al., 2013).While recalling past experiences, some participants prepare for the future by sharing thoughts with their family and friends (Sato-Komata et al., 2015).This, in some cases, also brought up concerns and worries about the unforeseeable future (Sato-Komata et al., 2015;Chen et al., 2019), which were seen as a threat to successful ageing.
Theme 10: Preparations for death This theme was mentioned in six articles.While life has its shares of hopes and concerns, death and dying were seen as an inevitable consequence of ageing and some studies stressed ideas about an easy, painless (Sato-Komata et al., 2015) and quick death (Tate et al., 2013).Ageing successfully meant not being afraid of death (Nosraty et al., 2015;Sato-Komata et al., 2015), but also accepting, acknowledging and preparing for death (Chen et al., 2019), as illustrated in this quote: 'When I was a younger, I didn't like the idea of dying, but now, I'm not so afraid anymore' (Sato-Komata et al., 2015, p. 590).
Regardless of fear of death or its acceptance, some made preparations for the future and saved for their funeral (Sato-Komata et al., 2015) and others anticipated life after death (von Faber et al., 2001).Some displayed denial and laughed when death was mentioned (Horder et al., 2013).The death of loved ones seemed to be a threat to their successful ageing (Horder et al., 2013;Tate et al., 2013).
In the presence of visual loss, the use of several coping and adaptive strategies to facilitate engagement in the community, minimise risk and reduce the experience of disability was discussed.These strategies included asking for help, being careful, concentrating and completing tasks slowly (McGrath et al., 2016).
Theme 12: Mental health, cognitive functioning and wellbeing Ten articles mentioned mental health and cognitive resources as an important component of successful ageing.Prerequisites for successful ageing were identified as cognitive functioning (Bassett et al., 2007;Horder et al., 2013;Nosraty et al., 2015;Sato-Komata et al., 2015;Lee et al., 2017;Chen et al., 2019), mental health (Tate et al., 2013;Nosraty et al., 2015), absence of dementia, preserved personality (von Faber et al., 2001;Horder et al., 2013), clear-headedness, having a good memory 1232 AC Badache et al. (Torres and Hammarstrom, 2009;Tate et al., 2013;Nosraty et al., 2015), being alert (Torres and Hammarstrom, 2009), being healthy and having an active mind (Bowling, 2006;Carr and Weir, 2017), and the ability to communicate (Tate et al., 2013).While some participants feared cognitive decline due to perceived loss of personality (von Faber et al., 2001), others accepted their cognitive decline and accepted that they had aged (Sato-Komata et al., 2015;Chen et al., 2019).Participants also believed that mind exercises (Bassett et al., 2007), such as intellectual stimulation and memory training (von Faber et al., 2001), continued learning and professional engagement (Horder et al., 2013;Tate et al., 2013;Nosraty et al., 2015;Carr and Weir, 2017;Chen et al., 2019), inquiry and curiosity were thought to lead to improved cognitive abilities (Bassett et al., 2007).Additionally, social engagement was related to cognitive engagement as social interaction was believed to keep one's mind stimulated (Carr and Weir, 2017).Finally, the absence of depression was also reported (von Faber et al., 2001;Nosraty et al., 2015), especially that wellbeing was equated with successful ageing (von Faber et al., 2001).The equation is conditioned by personality and character traits since they contribute to achieving and maintaining the feelings of wellbeing (von Faber et al., 2001).
A desired level of engagement in personally meaningful activities contributes positively to one's ability to age successfully (Horder et al., 2013;Carr and Weir, 2017).
Theme 13: Quality of life, wellness resources and lifestyle This theme was found in eight of the reviewed articles.Having a good quality of life was mentioned in three studies (Bowling, 2006;Bassett et al., 2007;Tate et al., 2013).This encompasses both a good lifestyle and the provision of basic needs; as an 82-year-old participant put it: 'Being well fed, well clothed, and well housed [QL2]' (Tate et al., 2013, p. 310).
Six articles mentioned lifestyle factors and choices as being important for ageing well.These factors refer to healthy lifestyle choices and behaviours (Bassett et al., 2007;Dionigi et al., 2011;Tate et al., 2013;McGrath et al., 2016;Carr and Weir, 2017).They included refraining from smoking, drinking and taking drugs (Bassett et al., 2007;Tate et al., 2013), maintaining a good diet and nutrition (Bassett et al., 2007;Dionigi et al., 2011;Tate et al., 2013), and having an active lifestyle and doing exercise (Bassett et al., 2007;Dionigi et al., 2011;Sato-Komata et al., 2015;Carr and Weir, 2017).Some participants described successful ageing as a lifestyle maintained with daily rituals (Sato-Komata et al., 2015), being neither rich nor poor (Sato-Komata et al., 2015), or getting sufficient sleep and rest (Bassett et al., 2007).Additionally, some considered preparing for new lifestyles by disposing of personal belongings and passing on work duties (Sato-Komata et al., 2015).Wellness resources were defined as having good physical and general health, intact cognitive functioning and independence, and being able to think clearly (Lee et al., 2017).
While, it is not always easy to socialise and make new friends in old age (Bassett et al., 2007;Horder et al., 2013), keeping a continuous and sustained relationship with one's physician was also seen to contribute to a long and healthy life (Bassett et al., 2007).
Theme 15: Spirituality and faith This theme was found in eight studies.In some studies spirituality refers to involvement in the church community (Bassett et al., 2007;Torres and Hammarstrom, 2009;Dionigi et al., 2011;Horder et al., 2013;Tate et al., 2013), but spirituality also referred to spiritual strength (Lee et al., 2017), spiritual health, fate, fortune (Bassett et al., 2007), and faith or religion (von Faber et al., 2001).Believing in god regardless of religion was seen as an important factor of successful ageing (Bassett et al., 2007;Tate et al., 2013;Nosraty et al., 2015).Spiritual growth and becoming a better person by accepting others were reported as crucial components of successful ageing (Nosraty et al., 2015).

Discussion
The present study reviewed the perceptions of successful ageing among older adults aged 75 and above, by providing a synthesis of the research on diverse older adults' meanings of successful ageing.Within the 15 thematic definitions identified, the components of successful ageing were categorised into contributing facilitators and inhibitors.Facilitators were more often reported than barriers, which can be explained by the fact that the term successful ageing is positively charged, and therefore older adults associate positive attributes with this term.These findings are supported by the idea of constructing a positive narrative by pointing out the positives associated with ageing, since the term 'successful ageing' was first introduced to counter ageism and age stereotyping caused by the overall discourse of decline (Rowe and Kahn, 1997;Calasanti, 2015).
It is acknowledged that successful ageing may be achieved even in the presence of chronic diseases and disabilities (Phelan et al., 2004;Young et al., 2009).The components identified in the reviewed studies support this claim and highlight the multi-dimensionality of successful ageing.Specifically, regardless of the country and study design, the reported themes in the reviewed studies show that older adults' beliefs about successful ageing are captured in more than health-related statements and include beliefs about psychological health, social relations, positivity and optimism, adaptation and acceptance of age-related changes, finances, spirituality and environmental influences, which is in line with previous research (Phelan et al., 2004;Iwamasa and Iwasaki, 2011;Cosco et al., 2013).Additional themes and components, which may be more age-dependent, and specific for the older adults 75 and above, were also found to be important for successful ageing.In this review, three novel successful ageing-related themes such as reflections on life and past experiences, preparations for death and environmental and system influences emerged.The first two have rarely been mentioned in previous reviews on successful ageing but it was reported in more than half of the studies reviewed in the current work.Reflecting on life, past experiences and anticipating the future seemed to be important for older adults.While certain life experiences such as career and education were considered to contribute to successful ageing, also living a joyful long life was deemed important by older adults.Regarding death, 75+ older adults reported wishes for an easy and painless death.The association between time left in life and chronological age might suggest that younger and older adults' definition of successful ageing is not the same, potentially due to perceived closeness to death and age-related differences in social goals.According to the SST, when time is perceived as limited, emotional goals and positive emotions become more important, even when associated with death (Carstensen et al., 1999;Lee et al., 2017).That is why older adults favour present-oriented goals that maximise wellbeing, such as investing in positive relationships with loved ones.In fact, having good social support and close relationships, a frequently reported theme that was also found in most of the reviewed studies, could be associated with declines in death anxiety over time (Chopik, 2017).
The second emergent theme is the environmental and system influences.This includes social and health-care services as well as living circumstances.While having access to medical services and receiving medical care were seen as important factors, some studies reported that participants felt neglected by the health-care systems and did not receive appropriate advice on the premise that their health problems are a natural cause of ageing.Considering the age group and the increased risk and fear of falling (Jung, 2008), favourable weather, season and lighting become relevant contributors to successful ageing, while ice and snow become a threat to successful ageing as these factors would impede older adults staying active.Environmental factors become more important as older adults move from early old age to an older phase in their life.The two themes of life and death, and environmental and system influences show that perceptions of successful ageing for older adults aged 75+ are not necessarily the same as those of younger counterparts.This study then highlights this difference in the perceptions of successful ageing, especially in relation to increased age-related vulnerability and closeness to death.
The theme of environmental and system influence alluded to some form of ageism experienced in health-care settings, in addition to some forms of system support.The remaining themes address successful ageing in terms of agential capacities (positive attitude, exercising and self-control), which translate into actions and behaviours on the part of older adults.Through the differing conceptions of successful ageing presented in these 15 articles, we reiterate the critical issues presented in Katz and Calasanti (2015).Successful ageing is still defined, even among the 75+ older adults, as a lifestyle choice that is associated with behaviours and volitions.These are occasionally constrained by material conditions and cumulative advantages and disadvantages.A wealth of critical literature in social gerontology has highlighted the struggle in applying a normative concept of successful ageing to a diverse older population (Martinson and Berridge, 2015), as age, gender, race and other life chances intersect to shape opportunities and inequalities in older age.However, it seems that even the oldest adults across cultures and backgrounds are accepting a larger share in their responsibility to age successfully, with diminishing state responsibilities.
This systematic review has some limitations.No grey literature was searched and therefore other relevant research might have been missed.Despite the methodological strategy to be more inclusive, due to the small samples and lack of studies conducted in the field, we were not able to highlight successful ageing views in relation to various socio-economic factors and could not capture the views of older adults from disadvantaged communities and settings.Another limitation of the field is that most studies are conducted in countries with high life expectancies, meaning that cultural variation may exist, suggesting that more research should be conducted.Furthermore, the sample size of many of the included studies was small and is therefore probably not generalisable to the whole population under study.

Research and policy directions
Our results highlight that the views of older adults aged 75+ are not to be condensed to those of their younger counterparts.More research should be conducted towards understanding the older age sub-groups' needs and their interpretations of successful ageing.Research should further explore additional components necessary for successful ageing considering the diversity/heterogeneity of the group of older adults by considering age groups, health, disability status and intersectionality aspects, such as gender, ethnicity, socio-economic status, sexual orientation, cultural indicators, education and values, as they contribute to the views of successful ageing.Furthermore, future research and policies related to successful ageing should acknowledge and reflect upon structural components such as the role of environments, access and opportunities for health care, nutrition and social policies that help or hinder the ability to age successfully.Within the context of feminisation of older age, it is well known that women have a higher life expectancy than men (Austad, 2006;Glei and Horiuchi, 2007;Zarulli et al., 2018).However, most of 1236 AC Badache et al.

Theme 2 :
Adaptation and continuity

Table 1 .
Study characteristics

Table 2 .
Factors, barriers and facilitators of successful ageing , 2015; Tate et al., 2013 Accepting current phase of life x Carr and Weir, 2017; Horder et al., 2013 Accepting what you cannot influence x Horder et al., 2013 Accepting death in a positive manner x Sato-Komata et al., 2015 Anticipating change x von Faber et al., 2001 Percentage 0 100 Theme 2: Adaptation and continuity: Adapting to the use of assistive devices x Tate et al., 2013 Living one day at a time x Tate et al., 2013 Planning for future support x Tate et al., 2013 Adapting to age-related changes x Horder et al., 2013; von Faber et al., 2001 ; Dionigi et al., 2011; Nosraty et al., 2015 Gratitude x Horder et al., 2013; Sato-Komata et al., 2015; Tate et al., 2013; von Faber et al., 2001

Table 3 .
Frequency of themes