Different measures of body weight as predictors of sickness absence

Excessive weight is associated with increased sickness absence from work due to obesity-linked health problems. However, it is not known which obesity measure best predicts sickness absence. First, we aimed to compare body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR) as predictors of sickness absence spells of various lengths. Second, we aimed to compare BMI based on self-reported and measured weight and height as a predictor of sickness absence to assess the validity of self-reported BMI.

The participants were 5750 employees of the City of Helsinki, aged 40-60 years, who were followed up on average for 4.8 years using the employer's register. Sickness absence spells were classified as self-certified short (1-3 days), medically certified medium length (4-14 days), and long (>14 days) absence spells.

All measures of body weight predicted sickness absence. The relative rates of long sickness absence in the highest quintile as compared to the lowest quintile varied in women from 1.62 (95% CI 1.35-1.94) to 1.89 (95% CI 1.62-2.23) and in men from 1.40 (95% CI 0.76-2.59) to 2.33 (95% CI 1.32-4.11). Differences in the predictive power of BMI and WC were small: both were more strongly associated with sickness absence than WHR. Self-reported BMI performed equally well as measured BMI.

BMI - measured or self-reported - is a valid anthropometric indicator of body weight and predictor of obesity-associated health-risks. Its use is feasible for research purposes as well as for the assessment of weight-related risks to work ability.