Work-Related Stress Was Not Associated with Increased Cancer Risk in a Population-Based Cohort Setting

Abstract

Background: Stress is a commonly perceived cause of cancer, but the evidence to date is limited and inconclusive. We examined work-related stress in relation to cancer incidence in a population-based cohort, with outcome data from Swedish national registries.

Methods: The study population included 113,057 participants in the Västerbotten Intervention Programme. HRs were estimated using Cox proportional hazards regression, for cancer overall and for types with ≥500 cases, and adjusting for several potential confounders. The primary exposure was prediagnostic work-related stress, using the well established Karasek job demand/control model. Demand and control variables were dichotomized at the median, and participants were classified according to combinations of these categories. We also considered social network and aspects of quality of life.

Results: "High-strain" work (high demand/low control) was not associated with cancer risk compared with "low-strain" work (low demand/high control): multivariable HR 1.01 [95% confidence interval (CI), 0.94-1.08] for men and 0.99 (95% CI, 0.92-1.07) for women. Results were also null for most cancer types assessed: prostate, breast, colorectal, lung, and gastrointestinal (GI). The risk of GI cancer was lower for "passive" (low demand/low control) versus "low-strain" work, particularly for colorectal cancer in women: multivariable HR 0.71 (95% CI, 0.55-0.91), but statistical significance was lost after adjustment for multiple testing.

Conclusions: The findings of this population-based, cohort study do not support a role for work-related stress in determining cancer risk.

Impact: This study helps fill an important knowledge gap given the common concern about stress as a risk factor for cancer.

Figure 1.

Västerbotten Intervention Programme (VIP) follow-up characteristics. A, Follow-up time distribution. B, Incident cancer cases distribution. C, Cumulative incidence of cancer estimated in the cohort by sex.

Figure 2.

HRs for cancer risk by work-related stress categories (Karasek) in men and women. Estimates from Cox proportional hazard models using age as time scale, adjusted for educational status, smoking status, BMI, recreational physical activity, and alcohol intake.

Figure 3.

Comparison of age-adjusted and multivariable adjusted HR for cancer risk by work-related stress (Karasek), social network, and quality of life indicators. Estimates from Cox proportional hazard models using age as time scale. Multivariable adjusted estimates were adjusted for educational status, smoking status, BMI, recreational physical activity, and alcohol intake. HRs are interpreted as the relative hazard of cancer at higher scores (indicating a higher risk of work-related stress, larger social network, and better quality of life), compared with lower scores. HRs differing from 1 with an unadjusted P < 0.05 are labelled.