Combinations of BMI and cardiorespiratory fitness categories: trends between 1995 and 2020 and associations with CVD incidence and mortality and all-cause mortality in 471 216 adults

Aims: To describe time trends in combinations of cardiorespiratory fitness (CRF) and body mass index (BMI) status, and to analyse their associations with cardiovascular disease (CVD) incidence and mortality and all-cause mortality.

Methods and results: Prospective cohort study with data from occupational health screenings in Swedish employees, including n = 471 216 (aged 18-74 years) between 1995 and 2020, and n = 169 989 in risk analyses. Cardiorespiratory fitness was estimated from a submaximal cycle test. High CRF was defined as top quartile, and low CRF as bottom quartile. Body mass index was used to define normal weight (18.5-24.9 kg/m2), overweight (25.0-29.9 kg/m2), and obesity (≥30 kg/m2). Outcome data (CVD incidence and mortality, all-cause mortality) were obtained from national registers. From 1995 to 2020, the combination of obesity + low CRF increased from 2.1% to 5.3% (relative increase 154%) whereas the combination of normal weight + high CRF decreased from 13.2% to 9.3% (-30%) (both P < 0.001). Negative changes were more pronounced in men, younger ages, and non-university educated. At the end of the period, prevalence of obesity + low CRF were higher in men vs. women (3.1% vs. 2.2%), older vs. younger (3.7% vs. 1.7%), and in non-university vs. university educated (5.0% vs. 0.3%), all P-value <0.001. Having a high CRF attenuated the risk of all three outcomes in all BMI categories, especially in individuals with obesity (hazard ratio 3.90 vs. 6.67 for CVD mortality). Both a low BMI and a high CRF prolonged age of onset for all three outcomes.

Conclusions: The combination of obesity with low CRF has increased markedly since the mid-90s, with clear implications for increased CVD morbidity and mortality, and all-cause mortality.