Associations Between Occupational Physical Activity and Left Ventricular Structure and Function over 25 Years in CARDIA

Aims: Leisure time physical activity (LTPA) confers cardiovascular health benefits, while occupational physical activity (OPA) may have paradoxically negative health associations. This study tested the explanatory hypothesis that unfavourable cardiac remodelling may result from chronic OPA-induced cardiovascular strain.

Methods And Results: Longitudinal associations of OPA and left ventricular (LV) structure and function were examined in 1462 participants {50.0% female, 56.4% White, aged 30.4 ± 3.4 years at baseline [Year 5 exam (1990-91)]} from the Coronary Artery Risk Development in Young Adults study. Left ventricular structure and function were measured as LV mass (LVMi), end-diastolic volume (LVEDVi), end-systolic volume (LVESVi), ejection fraction (LVEF), stroke volume (LVSVi), and e/a-wave ratio (EA ratio) via echocardiography at baseline and 25 years later. Occupational physical activity was reported at seven exams during the study period as months/year with 'vigorous job activities such as lifting, carrying, or digging' for ≥5 h/week. The 25-year OPA patterns were categorized into three trajectories: no OPA (n = 770), medium OPA (n = 410), and high OPA (n = 282). Linear regression estimated associations between OPA trajectories and echocardiogram variables at follow-up after adjusting for baseline values, individual demographic/health characteristics, and LTPA. Twenty-five-year OPA exposure was not significantly associated with LVMi, LVEDVi, LVSVi, or EA ratio (P > 0.05). However, higher LVESVi (β = 1.84, P < 0.05) and lower LVEF (β = -1.94, P < 0.05) were observed at follow-up among those in the high- vs. no-OPA trajectories.

Conclusion: The paradoxically adverse association of OPA with cardiovascular health was partially supported by null or adverse associations between high OPA and echocardiogram outcomes. Confirmation is needed using more precise OPA measures.