Dear Editor,

We appreciate the opportunity to respond to the letter to the editor by Patel et al. regarding our recently published article on the ‘Association between Selenium Intake and Cognitive Function among Older Adults in the US: National Health and Nutrition Examination Surveys 2011–2014’.^{(Reference Ferdous, Knol and Park1)} We are grateful to the authors for taking an interest in our work and providing constructive feedback.

In the letter, the authors acknowledged the importance of the study and provided a critical assessment of the study design. The authors suggested additional factors that can influence the effect of selenium such as the use of medications, diet, and the presence of viral infections. Medications such as chemotherapeutic and psychoactive agents and viral infections may potentiate reactive oxygen species (ROS) production, whereas a diet rich in antioxidants may help to neutralise excessive ROS.^{(Reference Vitali, Ripamonti and Roila2–Reference Morris, Tangney and Wang6)} Therefore, these are indeed important factors that can change neuronal structure and function by manipulating signalling pathways associated with ROS, in turn, can provide a better understanding of the relationship between selenium intake and cognitive function.

Our main goal in the currently published article^{(Reference Ferdous, Knol and Park1)} was to provide an association of selenium intake on cognitive function among community-dwelling older adults. From our analyses, we found the prevalence of inadequate selenium intake was roughly 5 %. Additionally, selenium intake was highly related to overall energy intake. In this population-based study, participants with inadequate selenium intake had an average energy intake of 851 kcal. If the two-dietary recalls were representative of usual intake over time, then risk factors for malnutrition should be considered in any future analyses.^{(Reference Yu, Yu and Liu7)} We are aware that dietary analysis is important to assess the interaction among nutrients and consequently the effect of selenium. However, this extensive analysis may be more appropriate to be approached as a separate dedicated study in the future. In addition, our study was a secondary analysis of the 2011–2014 National Health and Nutrition Examination Survey (NHANES) data which limited us from including the specific factors mentioned by the authors such as history of COVID infection, and use of anthracycline and platinum derivatives. Moreover, NHANES stopped conducting cognitive assessments after the year 2014.

We want to thank the authors again for their thoughtful critique and their commitment to advancing scientific discourse. The issues raised merit further investigation in future research efforts. There are limited epidemiological studies that have explored the potential neuroprotective effects of adequate selenium intake on cognitive function. We hope that our study can serve as a steppingstone for more comprehensive studies that can elucidate the complex relationship between selenium intake, cognitive function, and the various factors including nutritional, biological, medical, and socioeconomic status that can influence this association.