Introduction Hip circumference has been shown to be inversely associated with mortality. Reduced femoral fat or muscle atrophy in the gluteofemoral region in those with narrow hips has been proposed as explanations and thus, physical activity is likely to play an important role. The aim was to estimate the combined effects of hip circumference and leisure-time physical activity on all-cause mortality.

Methods We used a prospective population design with approximately 14 years' follow-up and estimated the HRs of all-cause mortality for combinations of physical activity and hip circumference. 3120 men and 4068 women aged 21 to 92 years without pre-existing diagnosis of diabetes, stroke, ischaemic heart disease, or cancer in 1991–1994 and with complete information on the variables of interest were included. They were followed until 2009 in the Danish Civil Registration System, with 1.5% loss to follow-up and 2334 deaths.

Results Hip circumference was inversely associated with all-cause mortality irrespective of physical activity. However, physical activity seemed to counterbalance some of the adverse health effects of a small hip circumference, with the excess mortality in the lower quartile of hip circumference being reduced by 41% in men (HRdiff: 1.41, 95% CI 1.14 to 1.74) and 40% in women (1.40, 1.14 to 1.71) when comparing physically inactive with the active. These associations were observed after adjustment for waist circumference, height, and weight change in the 6 months before the examination.

Conclusion A small hip circumference appears hazardous to survival. However, being physically active may counterbalance some of the hazardous effects of a small hip circumference.