A large-scale study on epidemiology and risk factors for chronic ankle instability in young adults.

Up to 40% of ankle sprains can result in chronic ankle instability (CAI). The prevalence of CAI and its association with body mass index (BMI) and height in the general young adult population has not been reported. The database records of young adults before recruitment into mandatory military service were studied. Information on the disability codes associated with CAI was retrieved. Logistic regression models were used to assess the association between the BMI and body height with various grades of CAI severity. The study cohort included 829,791 subjects (470,125 males and 359,666 females). The prevalence was 0.7% for mild CAI and 0.4% for severe instability in males and 0.3% and 0.4%, respectively, for females (p < .001). An increased BMI was associated with ankle instability in males (overweight, odds ratio [OR] 1.249, p < .001; obese, OR 1.418, p < .001) and females (overweight, OR 1.989 p < .001; obese, OR 2.754, p < .001). The body height was associated with an increased risk of CAI when the highest height quintile was compared with the lowest height quintile in both males (OR 2.443, p < .001) and females (OR 1.436, p < .001) for all levels of instability severity. The present study has shown a greater prevalence of CAI among males than females in a general healthy young adult population. CAI was associated with an increased BMI and greater body height for all grades of instability severity.