Aim In this study we assessed the influence of individual factors on self-reported exposures from The Danish Work and Health Study 2012 (DWHS2012) when controlled for job exposures assessed by The Lower Body JEM.¹

Methods We used multiple linear regression. The outcome was self-reported hours per day spent standing/walking according to DWHS2012. Predictors were corresponding expert based exposure estimates from The Lower Body JEM, which covers 499 Danish ISCO-88 (DISCO-88) codes, and general health, low back pain, work ability, body mass index, and smoking according to DWHS 2012.

Results There were 5973 observations with both self-reported and JEM-based exposures (3261 men, 2712 women). The JEM explained 15% of the variance of the self-reported standing/walking. The crude regression equation between JEM-based and self-reported standing/walking was: self-reported exposure in hours = 1.13 hours + 0.75 JEM exposure in hours. Non-smokers/ex-smokers, those reporting better work ability and those without low back pain underestimated their exposure by 0.2 hours, 0.3 hours, and 0.3 hours, respectively. People with low self-reported health overestimated their exposure by 0.1 hour.

The full model accounted for 17.4% of the variability in self-reported estimates of standing/walking.

Conclusion The JEM explained 15% of the variance of the self-reported standing/walking, and other factors contributed to a very small degree. Studies using self-reported standing/walking at work are likely to provide different results regarding health associations than studies using observed or objectively measured exposures, and should be used and interpreted with care.

Reference

1. Rubak TS, Svendsen SW, Andersen JH, Haahr JP, Kryger A, Jensen LD, et al. An expert-based job exposure matrix for large scale epidemiologic studies of primary hip and knee osteoarthritis: the Lower Body JEM. BMC Musculoskelet Disord2014;15:204.