Background: Some studies indicate that a large part of the beneficial effect of physical activity on mortality is confined to a threshold effect of participation.
Methods: Self-reported physical activity was investigated in relation to all-cause mortality in the Danish Diet, Cancer and Health cohort, including 29,129 women and 26,576 men aged 50–64 years at baseline 1993–1997. Using Cox proportional hazards models we investigated the associations between mortality rate and leisure time physical activity by exploring 1) participation (yes/no) in each type of activity; 2) a simple dose–response relationship with hours spent on each activity, supplemented with indicators of participation in each activity; and 3) inflexion or nonmonotonic dose–response relationships using linear splines.
Results: A total of 2696 women and 4044 men died through March 2010. We found lower mortality with participation in sports (for women, mortality rate ratio = 0.75, 95% confidence interval = 0.69–0.81; for men, 0.78, 0.73–0.84), cycling (for women, 0.77, 0.71–0.84; for men, 0.90, 0.84–0.96), or gardening (for women, 0.84, 0.78–0.91; for men, 0.73, 0.68–0.79) and in men participating in do-it-yourself activity (0.77, 0.71–0.84). A weak adverse dose response was seen for walking and gardening, but the association was small (1–2% increase in mortality per additional hour). We found no signs of inflexion or nonmonotonic effects of additional hours spent on each activity.
Conclusion: Mortality was lower with participation in specific leisure time physical activities, but not with more time spent on those activities. This could suggest that avoiding a sedative lifestyle is more important than a high volume of activity. Nonparticipation in these types of physical activity may be considered as risk factors.
From the aDanish Cancer Society Research Center, Copenhagen, Denmark; bDepartment of Public Health, Section of Epidemiology, Aarhus University, Aarhus, Denmark; and cDepartment of Cardiology, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark.
The study was supported by the Danish Cancer Society.
The authors report no conflicts of interest.
Correspondence: Nina Føns Johnsen, Danish Cancer Society Research Center, Strandboulevarden 49, DK-2100 Copenhagen Ø, Denmark. E-mail: email@example.com.
Received April 17, 2012
Accepted April 5, 2013