Little is known whether sex- and age differences in cardiorespiratory fitness translates into corresponding differences in sex- and age-related risk associations with cardiovascular disease (CVD) morbidity and all-cause mortality.
To investigate the sex- and age-specific associations, and the shape of the associations with a possible existing plateau, between cardiorespiratory fitness and CVD morbidity and all-cause mortality in a large sample of men and women of different ages free from CVD at baseline.
316.137 participants aged 18-74 years (45% women) who participated in a nationwide occupational health service screening between 1995 and 2015 were included. Cardiorespiratory fitness was expressed as relative maximal oxygen uptake (VO2max, in ml·min-1·kg-1), and estimated using a submaximal cycle test. Incident cases of a first-time CVD event and death from any cause were ascertained through the national in-hospital registry and the Swedish national cause of death registry.
Age-adjusted CVD morbidity and all-cause mortality incidence rates were inversely related to VO2max from low to high levels in both men and women and in all age-groups, with men, higher age and lower VO2max levels having higher incidence rates compared to their counterparts (Figure 1). Only in older men were the risk reduction less pronounced in the higher end of the VO2max spectrum, with a possible plateau effect (see figure). The risk (95% CI) for all-cause mortality and CVD morbidity decreased with 2.8% (2.3%-3.3%) and 3.2% (2.8%-3.5%) per increase in ml·min-1·kg-1 in the total population, and were greater in men (3.4% vs. 2.0%, p=0.003), in older ages (18-49 y: 2.4% vs. 50-59 y: 2.9% vs. 60-74y: 3.8%, non-significant between groups) and in participants with VO2max below median (4.7% vs. 1.4%, p<0.001) for all-cause mortality. Corresponding risk reductions for CVD morbidity were also higher in participants with VO2max below median (3.5% vs. 1.7%, p=0.004), but greater in young vs. old ages (18-49 y: 3.5% vs. 50-59 y: 3.1% vs. 60-74y: 2.4%, non-significant between groups) and similar in men compared to women (3.1% vs. 3.4%, non-sigificant).
In this large cohort of the Swedish working population, CVD morbidity and all-cause mortality were inversely related to cardiorespiratory fitness in both men and women and in all age-groups. Preventive actions to increase cardiorespiratory fitness is a clear public health priority, especially for vulnerable groups.