Leisure-time physical activity and all-cause mortality in an elderly cohort.
BACKGROUND
Physical activity is one of the mainstays of secondary prevention in people with heart disease. It is not well understood, however, how the presence of heart disease or a history of habitual exercise prior to the study modify any mortality-sparing effects of leisure-time physical activity.


METHODS
We analyzed data from a well-described cohort of subjects aged 54 years and older at intake (median age, 70 years) from Sonoma, CA, studied between 1993 and 2001 with mortality follow-up until 2003. A history-adjusted marginal structural model was used to obtain counterfactual excess risk estimates that were pooled across the different time points. Additive interaction was examined by comparing these excess risk estimates across strata of age, heart disease, and precohort physical activity.


RESULTS
Estimates of the excess risk for 2-year all-cause mortality comparing Centers for Disease Control and Prevention-recommended levels of current physical activity to lower levels of activity ranged from -0.7% to -4.9% among subjects younger than 75 years of age and from -7.8% to -14.8% among older subjects. Heart disease or precohort physical activity were not found to modify the effect of leisure-time physical activity.


CONCLUSIONS
Our data are consistent with the view that the mortality-sparing effect of recent physical activity is independent of the presence or absence of underlying cardiac disease and the pattern of past physical activity.
Bembom
Oliver
O
Division of Biostatistics, School of Public Health, University of California, Berkeley, California 94720-7358, USA.
van der Laan
Mark
M
Haight
Thaddeus
T
Tager
Ira
I