Tip of the iceberg: unveiling the impact on back disorders from cumulative physical job exposure and evaluating bias from the healthy worker effect using a nationwide longitudinal cohort study

PURPOSE

Longitudinal studies across various sectors with physically demanding jobs are notably absent in back disorder risk research. This study aimed to investigate the relationship between cumulative physical job exposure (PJE) and hospital-diagnosed back disorders among individuals in Denmark. To assess the healthy worker effect, we compared the cumulative risk estimate with results from a naive cross-sectional model ignoring PJE history.

METHODS

A nationwide longitudinal cohort study was conducted using Danish registers, encompassing individuals born between 1975 and 1978 and working in 1996. Cumulative PJE was measured with a 10-year look-back period for each year 2006-2017. PJE consisted of lower-body occupational exposures, including the total weight lifted, stand/sit ratio, and the frequency of lifting more than 20 kg per day from a job exposure matrix. Odds ratio for back disorders was estimated for each year and all years combined.

RESULTS

The results unveiled a significant 31% increase in the risk of hospital-diagnosed back disorders after 4 years of cumulative PJE. The lowest risk (7%) was observed for incident back disorders with 1 year of exposure, suggesting a healthy worker effect. Nevertheless, this risk is still significantly elevated. This cumulative estimate is fourfold the estimate from the 2006 naive cross section model.

CONCLUSION

Our study clearly demonstrates an 31% increase in the risk of hospital-diagnosed back disorders with just 4 years of PJE over a 10-year period. Further, we find that cross-sectional studies strongly underestimate the risk of back disorders due to the healthy worker effect.

Back disorder incidence and occupation in Denmark: a cross-sectional register-based study

PURPOSE

The purpose of the present paper is (1) to describe the occupational distribution of persons with incident back disorders and (2) to determine the incidence rate ratio (RR) for back pain amongst patients working in specific occupation groups.

METHODS

Using Danish registries, a total of 20,921 employed persons with incidents back disorders aged 18-64 years were identified in 2016 based on the inclusion criteria from the Danish Back Register. RR was estimated to test for differences in incident back disorder diagnoses across occupations. Pearson's Chi-square test was used to test for homogeneity in back disorder incidence across occupations.

RESULTS

The distribution of back disorder incidence for employed is above the distribution of employment in the background population for all age groups above 35 years. For employed women the three occupation groups with the highest RR of back pain incidence are: 'water, sewage and waste'; 'residential institutions and home care'; and 'transport of passengers', while similarly, amongst employed men: 'hairdressers and other personal care'; 'hospitals'; and 'cleaning'. RR of incident back pain disorders is lowest for women employed in 'universities and research' and for men employed in 'IT and telecommunications'.

CONCLUSIONS

This study is the first to investigate the occupational status and RR of back disorder incidence across occupation groups in Denmark. The distribution of back pain disorder incidents in the cross-sectional study is weighted to occupation groups involving hard physical activity. This evidence may be useful for considering work environment or pension reforms. These slides can be retrieved under Electronic Supplementary Material.

Predictors of back disorder among Almeda textile factory workers, North Ethiopia

Objectives

To guide the development of targeted interventions for the prevention of work-related back pain, this manuscript estimates the prevalence of back pain and its association with a variety of risk factors among Almeda textile factory production works from March to April 2015. An institutional—based cross-sectional study was carried out in Almeda textile factory, North Ethiopia. Randomly selected workers were administered a structured questionnaire about their socio-economic status, lifestyle, working conditions, back pain and selected risk factors. The data was entered to Epi Info 3.5.4 version and analyzed using SPSS version 16. Descriptive statistics were done to characterize the study participants. Bivariate and multiple logistic regressions were fitted to control confounding variables. Adjusted odds ratio with 95% confidence intervals was computed.

Results

The prevalence of work-related musculoskeletal disorders was 53.1%. Gender, age, years of service, lack of physical activity, unavailability of adjustable chair, work-load and poor light were significantly associated with increased risk of back pain. The high prevalence of work-related back pain disorder implies that; habit of doing physical exercise, availing adjustable chair and light at the working place, are key issues which require specific interventions.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3440-4) contains supplementary material, which is available to authorized users.