Does the benefit on survival from leisure time physical activity depend on physical activity at work? A prospective cohort study

Abstract

Purpose: To investigate if persons with high physical activity at work have the same benefits from leisure time physical activity as persons with sedentary work.

Methods: In the Copenhagen City Heart Study, a prospective cohort of 7,411 males and 8,916 females aged 25-66 years without known cardiovascular disease at entry in 1976-78, 1981-83, 1991-94, or 2001-03, the authors analyzed with sex-stratified multivariate Cox proportional hazards regression the association between leisure time physical activity and cardiovascular and all-cause mortality among individuals with different levels of occupational physical activity.

Results: During a median follow-up of 22.4 years, 4,003 individuals died from cardiovascular disease and 8,935 from all-causes. Irrespective of level of occupational physical activity, a consistently lower risk with increasing leisure time physical activity was found for both cardiovascular and all-cause mortality among both men and women. Compared to low leisure time physical activity, the survival benefit ranged from 1.5-3.6 years for moderate and 2.6-4.7 years for high leisure time physical activity among the different levels of occupational physical activity.

Conclusion: Public campaigns and initiatives for increasing physical activity in the working population should target everybody, irrespective of physical activity at work.

Figure 1. Flow diagram of the study population in the Copenhagen City Heart Study.

The entire study sample consisted of persons participating in at least one of the four examinations (i.e. some persons participated in multiple examinations) in the Copenhagen City Heart Study who were free of previous cardiovascular disease (CVD) at their first examination in the study.

Figure 2. Risk (Cox regression Hazard ration with 95% confidence intervals) for cardiovascular mortality and all-cause mortality from leisure time physical activity adjusted for age, calendar time, BMI, smoking, alcohol consumption, cholesterol, systolic blood pressure, blood pressure medication, diabetes and household income stratified on occupational physical activity among males (n = 7,411) and females (n = 8,916) between 20 and 67 years of age without a history of cardiovascular disorders in the Copenhagen City Heart Study. *

Adjusted for age, calendar time, BMI, smoking, alcohol consumption, cholesterol, systolic blood pressure, blood pressure medication, diabetes and household income, survival benefit was calculated for a healthy average person (mean value of BMI, systolic blood pressure, cholesterol, household income, and a never smoker, without diabetes and not taking blood pressure medication, and consuming alcohol on a monthly basis) by integrating the survival function estimated in the Cox models.