Introduction While a body of literature identifies relations between injury occurrence and resulting stress, literature relevant to relations between work factors and stress and injury occurrence is limited.

Objectives To identify the potential relations between: 1) work-related factors and stress and 2) stress and depression and injury outcomes in a high risk, understudied population.

Methods Specially designed questionnaires were disseminated to 1,200 full-time unionized janitors to collect information on their injury occurrences, personal characteristics, health history, and work-related exposures, for two sequential six-month periods. Risk ratios (RRs) and 95% confidence intervals (CIs) were calculated using multivariable Poisson regression with robust error variances, and included bias adjustment for non-response and adjustment for within-person correlation using general estimating equations (GEEs).

Results 527 total observations among 390 janitors identified associations between the following exposures and high/low stress outcome (collapsed 5 point Likert scale – often/very much versus (vs) not at all/very little/sometimes): work environment factors (range = 1, terrible/unhappy/mostly dissatisfied; 2, mixed feelings; 3, mostly satisfied/pleased delighted) how they felt about their job (1 vs 3 - RR 4.50; CI 2.38, 8.52); where they worked (1 vs 3 - RR 3.46; CI 2.03, 5.92); resources available for their job (1 vs 3 - RR 1.77 CI 1.14, 2.76); and job mentally or physically demanding (high/very high vs very low/low/medium demand) RR 2.49; CI 1.26, 4.93 and RR 3.74; CI 1.37, 10.25, respectively. High vs low stress exposure was associated with outcomes: diagnosed depression yes/no (RR 4.79; CI 2.22, 10.36); and risk of injury (RR 1.45; CI 1.00, 2.10).

Conclusions This analysis enabled identification of: work-related factors associated with reported stress; the relation between stress and depression; and risk of injury among those reporting stress levels. These findings serve as a basis for future research and relevant interventions to facilitate optimal working environments.