UCL RESEARCH DEPARTMENT OF EPIDEMIOLOGY AND PUBLIC HEALTH

There is increasing evidence of an association between health behaviors and cognitive aging. Smoking, alcohol, physical activity and nutrition have all been found to be associated with poor cognitive function and dementia. The extent to which health behaviors can explain cognitive aging trajectories is of substantial public health relevance, particularly as they may be ‘the’ key modifiable risk factors for dementia. The overarching aim of this proposal is to examine the combined impact of health behaviors over the adult lifecourse in determining cognitive aging trajectories starting from midlife. The unique feature of this proposal is three repeat assessments of cognitive function (funding for 4th wave under review) using a comprehensive test battery and a first assessment carried out in midlife allowing an examination of the inflection point in changes in cognitive functioning.

The specific aims are:

1. Health behaviors as determinants of cognitive aging: To examine the combined impact of smoking, alcohol consumption, physical activity and diet on decline in cognitive function (cognitive aging). The intention is to disentangle the exposure-outcome associations in terms of a) timing, ie the combined effect of health behaviors in early, mid and late midlife on cognitive aging; and b) duration, ie whether the combined impact of health behaviors accumulates over time.

2. Impact of change in health behaviors on cognitive aging: To examine the dynamic association between health behaviors we will analyze the extent to which change in one behavior leads to changes in others and the extent to which these changes influence cognitive aging. In addition, we will examine whether changes in specific clusters of risk factors are particularly detrimental for cognitive aging and whether changes in particular health behaviors, such as smoking, act as triggers for a cascade of changes.

3. Bidirectional associations between health behaviors and cognitive aging starting in midlife: To test the bidirectional associations between cognitive aging and changes in health behaviors in order to estimate the relative importance of these effects and to determine the dominant temporal direction. Three concurrent assessments of health behaviors and cognition over 10 years allow the assessment of bidirectional effects.

4. Explanatory mechanisms: A core focus is on understanding the extent to which biological changes, such as those in vascular risk factors and diseases, explain the association between health behaviors and cognitive aging. We will also examine the role played by two potential effect modifiers of the association between health behaviors and cognitive aging: socioeconomic status (SES) and the apolipoprotein E (APOE) e4 allele.

This proposal is based primarily on the British Whitehall II study but the research team is composed of scientists based in France as well as the UK, providing us with the opportunity to validate some of our results (aim 1) in data from the French GAZEL study.