The “Futile Labour” Paradox: occupational physical activity fails to offset diabetes burden and is associated with microvascular stress signals in rural older adults

Background Physical activity is widely promoted as a cornerstone of healthy ageing; however, this assumption largely derives from leisure-time exercise and may not apply to labour-dependent older populations. In rural settings, occupational physical activity (OPA) is often necessity-driven, prolonged, and embedded within structural constraints, yet its associations with metabolic and vascular outcomes in later life remain poorly understood. Methods We conducted a community-based cross-sectional study of 2,258 adults aged ≥65 years from a representative agricultural region in Northeast China. Labour-type physical activity was classified as inactive, moderate, or high intensity. To mitigate underdiagnosis, we defined total diabetes burden as either diagnosed diabetes or undiagnosed hyperglycemia. Systemic insulin resistance was assessed using the triglyceride–glucose (TyG) index. Urine occult blood (UOB) positivity was analyzed as an exploratory marker compatible with physiological stress. Associations were examined using modified Poisson regression with robust variance, robust linear regression, and prespecified sensitivity analyses. Results High-intensity labour was associated with a modest reduction in insulin resistance among individuals without diagnosed diabetes ( β = −0.079, p = 0.005) and a lower prevalence of undiagnosed hyperglycemia (PR 0.69, 95% CI 0.53–0.88). In contrast, high-intensity labour was more common among individuals with diagnosed diabetes (PR 1.43, 95% CI 1.11–1.85). These opposing associations did not show a significant net association with total diabetes burden (PR 0.99, p = 0.912). Independently of metabolic status, high-intensity labour was associated with a higher prevalence of UOB positivity (PR 1.25, 95% CI 1.09–1.44). Conclusion In labour-dependent rural older adults, heavy occupational labour may not confer metabolic benefit at the population level and is independently associated with a microvascular stress–related signal. This “Futile Labour Paradox” challenges the assumption that physical activity is uniformly beneficial in later life and underscores the need to distinguish occupational labour from discretionary exercise.