Relationship between cumulative exposure to occupational lifting throughout working life and risk of ischemic heart disease in men and women. The Copenhagen Aging and Midlife Biobank.

Ischemic heart disease (IHD) causes mortality and morbidity. High levels of occupational physical activity (OPA) increases IHD risk, and occupational lifting (OL) is suggested as a detrimental OPA exposure. This study investigated the association between accumulated OL throughout working life, and risk for IHD, and potential sex and hypertension differences. Data from Copenhagen Ageing and Midlife Biobank linked to register-based information on incident IHD during 9 years follow-up in the Danish National Patient Registry were included. The outcome was the odds of IHD from baseline (2009-2011) to end of follow-up (2018), among participants without IHD at baseline. Accumulated OL was assessed by linking occupational codes to a Job Exposure Matrix, creating a measure in ton-years (lifting 1,000 kg/day/year). Multivariable logistic regression tested associations between level of accumulated OL and IHD, among the 6,606 included individuals (68% men). During follow-up, 7.3% men and 3.6% women were hospitalized with IHD. Among all participants, the odds for IHD were 47% (OR 1.47, 95% CI 1.05-2.06) higher among those with ≥5 to <10 ton-years, 39% (OR 1.39, 95% CI 1.06-1.83) higher among those with ≥10 to <30 ton-years, and 62% (OR 1.62, 95% CI 1.18-2.22) higher among those with ≥30 ton-years, compared to no accumulated OL. However, these increased odds were in the same direction in the fully-adjusted model but statistically insignificant, ≥5 to <10 ton-years OR 1.28, 95% CI 0.88-1.88; ≥10 to <30 ton-years OR 1.20, 95% CI 0.85-1.69; and ≥30 ton-years OR 1.22, 95% CI 0.81-1.84. No statistically significant interactions, nor any associations, between OL and sex, or hypertension were seen.

Prospective relationship between occupational physical activity and risk of ischaemic heart disease: are men and women differently affected?

AIMS: High occupational physical activity (OPA) seems to increase risk of cardiovascular diseases among men. However, findings are mixed, and it is not known if women are differently affected. Therefore, the aim of this study is to investigate the relationship between OPA and risk for ischaemic heart disease (IHD), and whether it differs across sex. METHODS AND RESULTS: This prospective cohort study was based on 1399 women and 1706 men, aged 30-61 years, participating in the Danish Monica 1 study in 1982-84, actively employed, without prior IHD and answering an OPA question. The information on incidence of IHD, before and during the 34-years follow-up, was retrieved by individual linkage to the Danish National Patient Registry. Cox proportional hazards models were used to investigate the association between OPA and IHD. Compared to women with sedentary work, women in all other OPA categories had lower hazard ratio (HR) for IHD. Among men, the risk of IHD was 22% higher among those with light OPA, and 42% and 46% higher among those with moderate OPA with some lifting or strenuous work with heavy lifting, respectively, compared to men with sedentary OPA. Compared to women with sedentary work, HR for IHD was higher among men in all OPA categories. There was statistically significant interaction between OPA and sex. CONCLUSION: Demanding or strenuous OPA seems to be a risk factor for IHD among men, whereas a higher level of OPA seems to protect women from IHD. This emphasizes the importance of taking sex differences into account in studies of health effects of OPA.

In the Danish Monica I study among 1399 women and 1706 men, we investigated whether high physical activity at work was associated with higher risk of ischaemic heart disease and whether this association was different among men and women. The association between occupational physical activity and ischaemic heart disease was different among men and women. High physical activity at work was associated with around 45% higher risk of ischaemic heart disease in men, but with around 65% lower risk in women. The underlying mechanisms for this difference, e.g. differences in exposure and physiology, should be further investigated in future studies.

Does influence at work modify the relation between high occupational physical activity and risk of heart disease in women?

PURPOSE: To investigate whether influence at work modifies the association between demanding and strenuous occupational physical activity (OPA) and risk of ischaemic heart disease (IHD). METHODS: A sample of 12,093 nurses aged 45-64 years from the Danish Nurse Cohort Study was followed for 20.6 years by individual linkage to incident IHD in the Danish National Patient Registry. Information on OPA, influence at work, other occupational factors and known risk factors for IHD was collected by self-report in 1993. RESULTS: During follow-up 869 nurses were hospitalised with incident IHD. Nurses exposed to strenuous OPA and low influence at work had a 46% increased risk of IHD [hazard ratio (HR) 1.46 (95% confidence interval (CI) 1.02-2.09)] compared to the reference group of nurses with moderate OPA and high influence at work. Nurses exposed to strenuous OPA and high influence at work were not at an increased risk of IHD [HR 1.10 (95% CI 0.59-2.06)]. An additive hazards model showed there were 18.0 (95% CI -0.01 to 36.0) additional cases of IHD per 10,000 person years among nurses with strenuous OPA and low influence at work compared to nurses with moderate OPA and high influence at work. A detrimental additive interaction between strenuous OPA and low influence at work that could explain the additional cases of IHD among nurses with strenuous OPA and low influence at work was indicated. CONCLUSION: The findings suggest that high influence at work may buffer some of the adverse effects of strenuous OPA on risk of IHD.

High occupational physical activity and risk of ischaemic heart disease in women: the interplay with physical activity during leisure time.

BACKGROUND: Recent studies indicate that physically demanding work is a risk factor for heart disease among men, especially those with low or moderate physical activity during leisure time. Among women, present evidence is inconclusive. DESIGN: The design was a prospective cohort study. METHODS: This investigation in the Danish Nurse Cohort Study included 12,093 female nurses aged 45-64 years, who answered a self-report questionnaire on physical activity at work and during leisure time, known risk factors for ischaemic heart disease (IHD) and occupational factors at baseline in 1993. Information on the 15-year incidence of IHD was obtained by individual linkage in the National Register of Hospital Discharges to 2008. RESULTS: During follow-up 580 participants were hospitalised with IHD. A significant interaction between occupational and leisure time physical activity was found with the lowest risk of IHD among nurses with the combination of moderate physical activity at work and vigorous physical activity during leisure time. Compared to this group high physical activity at work was associated with a higher risk of IHD at all levels of physical activity during leisure time increasing from hazard ratio 1.75 (95% confidence interval (CI) 1.10-2.80) among nurses with vigorous physical activity during leisure time to 2.65 (95% CI 1.44-4.88) among nurses being sedentary during leisure time. CONCLUSIONS: This study among Danish nurses suggests that high physical activity at work is a risk factor for IHD among women. Vigorous physical activity during leisure time lowered but did not completely counteract the adverse effect of occupational physical activity on risk of IHD.