I study ageing and diseases associated with ageing from an epidemiological perspective. I am particularly interested in the ways in which exposures across the life course result in chronic disease and disability at older ages. By the use of field investigation of large numbers of people, randomly selected from the general population, collection of clinical, social, behavioural, and biological data, and subsequent statistical analysis, the occurrence of common chronic diseases is studied in terms of geographic distribution, temporal patterns. Associations with individual risk factors are also explored. This information can then be used to increase our understanding of causation of disease in older age, and from this to develop interventions and policies aimed at improving survival in good health at older ages. My interest in neuroscience stems from the study of stroke and cognitive decline, both common in older age, and associated with considerable consequences for both the individual and society. In both high and low income countries, ageing is occurring and consequently stroke and cognitive impairment are growing challenges. While much is now known about the causes of stroke, the reasons for the downward secular trend in occurrence is not understood and neither is the geographic variation, suggesting that continued efforts to understand causes of stroke may be rewarded by novel means of prevention. Determining the causes of cognitive impairment, particularly before it becomes symptomatic (when intervention may be more feasible) is of great importance. Epidemiological research has the potential to identify ways to slow or even prevent cognitive impairment and stroke, and lead to improvements in treatment and care.