Key points

• Adults aged 15 to 64 years account for a sizeable proportion ofthe population (over 60%) both worldwide and within the UK.

• Non-communicable diseases are the leading causes of death indeveloped countries whereas in developing countries, communicablediseases, maternal, perinatal and nutritional conditions and injuriesare the leading causes of death.

• Within the UK, cancers, cardiovascular diseases, diabetesmellitus, mental illness and obesity are significant public healthproblems in this age group.

• Although national policies are already in place to tackle theseconditions, concerted health-improvement efforts with engagement oflocal populations are required to make a significant impact on theburden of ill health.

Introduction

Approximately 66% of the world’s population in 2010 was estimated tobe aged between 15 and 64 years, with a male:female ratio of 1.02. Inless-developed regions of the world, this age group comprises 65% of thetotal population whereas in the more developed regions it comprises about68% [1].

In 2009, 65% of the UK population were aged between 15 and 64 years. Althoughthe total UK population increased by 10% between 1984 and 2009, theproportion of the population aged 15–64 years increased only by 1% [2]. Theold-age dependency ratio (number of people aged 65 or more for every 100people aged 15–64) in the UK was 24 in 2009; this is close to the EU averagebut is projected to rise to 39 by 2035 as the population ages (see Chapter14).