The relationship between aging and disease

Nutrition, ageing and ill health

There are physical, mental, social and environmental changes which take place with ageing; for example, decreased physical activity, increase in body fat, decrease in lean body mass and consequently decreased energy intake may be associated with physiological functions that affect metabolism, nutrient intake, physical activity and risk of disease. There are now many studies which have found that undernutrition is prevalent and often unrecognized in patients admitted to hospitals and institutions. There is also evidence which links protein-energy undernutrition or its markers with clinical outcomes in acute and non-acute hospital settings and that nutritional supplements can improve outcomes in some of these settings. However, most clinically-available nutrition screening instruments lack sensitivity and specificity, and abnormal nutritional indicators may simply reflect effects of age, functional disability, or severe underlying disease. Thus, causal relationship cannot be assumed without a sufficiently powerful intervention study which adequately adjusts for the effects of non-nutritional factors, such as the number and severity of co-morbid conditions on clinical outcome.

Human senescence

Human life expectancy has increased dramatically through improvements in public health, housing, nutrition and general living standards. Lifespan is now limited chiefly by intrinsic senescence and its associated frailty and diseases. Understanding the biological basis of the ageing process is a major scientific challenge that will require integration of molecular, cellular, genetic and physiological approaches. This article reviews progress that has been made to date, particularly with regard to the genetic contribution to senescence and longevity, and assesses the scale of the task that remains.