Physical activity and genetic influences in risk factors and aging: a study on twins.

Abstract

The association between physical activity and a decreased risk of age-correlated diseases appears to be well established. Nevertheless, the relation between past life style and current health in the elderly is likely to be affected by interactions of environmental and genetic factors in mediating the effects of exercise on disease prevention. As a contribution to this general issue, a retrospective twin study was undertaken so as to take advantage of the classical twin method in assessing genetic influences on health status in the elderly. A more specific aim was to possibly identify and compare genetically identical elderly twins with substantial differences in previous exposure to physical activity, but otherwise similar life style factors and events, thereby allowing the application of the co-twin case-control method, a powerful experimental approach in which even a few cases may prove significant. The study involved the assessment of general health status (based on structured interviews, clinical examination and several functional and laboratory analyses) and life style in 27 male twin pairs, aged 71.0 +/- 2.6 and classified (through DNA analysis) as 13 monozygotic and 14 dizygotic pairs. Past and present physical activity were evaluated through the Modified Baecke Questionnaire for Older Adults. In general, higher intrapair correlations in monozygotic than dizygotic pairs for almost all clinical variables were found, thereby confirming the relevance of genetic effects. More specifically, five monozygotic pairs discordant for past physical activity were found: contrary to expectations and, notwithstanding this major difference, they did not appear to be less similar than other pairs with respect to general health status. More data are clearly needed, and the implications of these findings, if confirmed, may leave room for complex interpretations. Tentatively, however, one might be led to conclude that whatever protective role physical activity and other life style variables clearly play in general health, this may in the end be unable to offset strong genetic dispositions, particularly so when it comes to major risk factors, which, after all, is perhaps only reasonable.