Academic journal article Scandinavian Journal of Work, Environment & Health

Does a History of Physical Exposures at Work Affect Hand-Grip Strength in Midlife? A Retrospective Cohort Study in Denmark

Academic journal article Scandinavian Journal of Work, Environment & Health

Does a History of Physical Exposures at Work Affect Hand-Grip Strength in Midlife? A Retrospective Cohort Study in Denmark

Article excerpt

Möller A, Reventlow S, Hansen ÂM, Andersen LL, Siersma V, Lund R, Avlund K, Andersen JH, Mortensen OS. Does a history of physical exposures at work affect hand-grip strength in midlife? A retrospective cohort study in Denmark. Scand J Work Environ Health. 2013;39(6):599-608. doi:10.5271/sjweh.3368

Objective The aim of this cohort study was to examine associations between physical exposures throughout working life and hand-grip strength (HGS) in midlife.

Methods The Copenhagen Aging and Midlife Biobank (CAMB) provided data about employment and HGS for 3843 Danes. Individual job histories, including duration of employment in specific jobs, were assigned exposures from a job exposure matrix. Exposures were standardized to ton-years (lifting 1000 kg each day in one year), stand-years (standing/walking for six hours each day in one year) and kneel-years (kneeling for one hour each day in one year). The effects of exposure-years on HGS were analyzed as linear effects and cubic splines in multivariate regression models, adjusted for potential confounders.

Results Mean age was 59 years among both genders and HGS was 49.19 kg [standard deviation (SD) 8.42] and 30.61 kg (SD 5.49) among men and women, respectively. Among men, exposure to kneel-years was associated with higher HGS [>0.030 kg (P=0.007) per exposure-year]. Ton- and stand-years were not associated with HGS among either men or women in linear analyses. In spline regression analyses, associations between ton- and stand-years and HGS were non-linear and primarily positive among men. Among women, the associations were non-linear and, according to ton-years, primarily negatively associated with HGS but statistically insignificant.

Conclusion A history of physical exposures at work explained only a minor part of the variation in HGS, though exposure to kneeling throughout working life was associated with a slightly higher HGS among men. Exposure to lifting and standing/walking was not associated with HGS.

Key terms ergonomics; muscle strength; musculoskeletal aging; occupational; physical activity

The influence of work-related exposures on muscle strength has been discussed since the 1980s, where occu- pational physical activity was thought to strengthen manual workers (1). Since then the focus has been on the deteriorating effects of physical exposures, which are now known to be important risk factors in the development of musculoskeletal symptoms and diseases (2, 3). It has been suggested that exposure and musculoskeletal injury (or deterioration) follow a dose-response relationship (4), but threshold values for duration or intensity of expo- sure have not been established (3, 5). One explanation for this is the multi-factorial origin of musculoskeletal symptoms and diseases, including genetic, morphologi- cal, psychological, and biomechanical risk factors (4, 5). Theories about cumulative load suggest "wear and tear" as an important factor in the deterioration of the musculoskeletal system (4,5), and the underlying muscu- loskeletal aging process also plays an important role (6). Few studies have used the objective outcomes of physical function as signs of occupational musculoskeletal dete- rioration though objective measures have been suggested to be less biased than self-reports (7). Hand-grip strength (HGS) is a simple objective measure of muscle strength and a well-known predictor of morbidity and disability among older people (8-10) and of mortality among both younger (11) and older age groups (8,12,13). A positive association between manual work and HGS was shown among men with a high workload compared to men with a lower workload in a cross-sectional study (14), sug- gesting a training effect. A few longitudinal studies have had contradictory results. Savinainen et al (15) found no association between perceived physical workload at baseline and HGS after 22 years of follow-up (mean age 67.3 at follow-up); while Stenholm et al (16) found that self-reports of physical work at baseline were associated with lower HGS at follow-up 22 years later (mean age 48 at follow-up). …

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