Reduced Body Flexibility Is Associated With Poor Survival in Middle-Aged Men and Women: A Prospective Cohort Study

Objectives: Flexibility is recognized as one of the components of physical fitness and commonly included as part of exercise prescriptions for all ages. However, limited data exist regarding the relationship between flexibility and survival. We evaluated the sex-specific nature and magnitude of the associations between body flexibility and natural and non-COVID-19 mortality in a middle-aged cohort of men and women. Design: Prospective cohort study. Methods: Anthropometric, health and vital data from 3139 (66% men) individuals aged 46-65 years spanning from March 1994 to October 2022 were available. A body flexibility score, termed Flexindex, was derived from a combination of 20 movements (scored 0-4) involving seven different joints, resulting in a score range of 0-80. Kaplan-Meier survival curves were obtained, and unadjusted and adjusted hazard ratios (HRs) for mortality estimated. Results: During a mean follow-up of 12.9 years, 302 individuals (9.6%) comprising 224 men/78 women died. Flexindex was 35% higher in women compared to men (mean +/- SD: 41.1 +/- 9.4 vs. 30.5 +/- 8.7; p < 0.001) and exhibited an inverse relationship with mortality risk in both sexes (p < 0.001). Following adjustment for age, body mass index, and health status, the HR (95% CI) for mortality comparing upper and bottom of distributions of Flexindex were 1.87 (1.50-2.33; p < 0.001) for men and 4.78 (1.23-31.71; p = 0.047) for women. Conclusions: A component of physical fitness-body flexibility-as assessed by the Flexindex is strongly and inversely associated with natural and non-COVID-19 mortality risk in middle-aged men and women. Future studies should assess whether training-induced flexibility gains are related to longer survival.