Independent effects of sleep duration and body mass index on the risk of a work-related injury: Evidence from the US National Health Interview Survey (2004-2010)

Introduction: To answer whether BMI modifies the effect of short sleep or has an independent effect on work-related injury risk, we examined the risk of a work-related injury as a function of total daily sleep time and BMI using the US National Health Interview Survey (NHIS).

Methods: Data were pooled for the seven-year NHIS survey period from 2004-2010 for 101 891 "employed" adult subjects (51.7% male; mean [SEM] age 41.1 [.08] yrs) with data on both sleep and BMI. To account for the complex sampling design, including stratification, clustering, and unequal weighting, weighted multiple logistic regression was used to estimate the risk of a work-related injury.

Results: No significant interaction was found between usual daily sleep duration and BMI (p = .72). Statistically significant covariates included age, sex, weekly work hours, occupation, and if being paid hourly. The lowest categories of usual sleep duration (<6 and 6 - 6.9 h) showed significantly elevated injury risks than the referent category (7-8 h sleep), whereas sleeping more than 7-8 h, did not significantly elevate risk. With regards to BMI, the adjusted injury risk OR comparing workers who were obese (BMI: 30+) to healthy weight workers (BMI: <25) was 1.34 (95% CI:1.09-1.66), whereas the risk in comparing overweight workers (BMI: 25-29.99) to healthy weight, risk was elevated, but not statistically significant (OR = 1.08; 95% CI:.88-1.33).

Discussion and Conclusions: The results from this large representative sample of US workers suggest an independent risk of sleep duration and BMI on work-related injury risk.