"Objectives The aim of this study was to examine the risk of work injury associated with changes in shift schedules and identify whether work injury risks differ between men and women.Methods Longitudinal panels from the Survey of Labor and Income Dynamics were used to describe work schedule patterns over a 6-year period among a representative sample of Canadian workers (N=19 131). Cox regression was used to estimate the risk of work injury among workers who (i) switched from regular day to nonstandard shifts, (ii) switched from nonstandard to day shifts and (iii) remained in nonstandard shifts, compared with (iv) those who worked regular day shifts only. Gender differences were examined in separate stratified analyses. Adjustments were made for potential respondent and occupational confounders. Results Increased injury risk was observed among those who: switched from day to nonstandard shifts [hazard ratio (HR) 2.60, 95% confidence interval (95% CI) 1.79–3.77], switched from nonstandard to days (HR 2.36, 95% CI 1.62–3.49), and worked nonstandard shifts only (HR 1.44, 95% CI 1.23–1.70). For women, work injury risk was higher among those who switched shifts (days to nonstandard HR 3.10, 95% CI 1.76–5.46; nonstandard to days HR 2.31, 95% CI 1.36–3.91), or worked nonstandard shifts only (HR 1.85, 95% CI 1.44–2.37) compared to day schedules. However, for men the risk of injury was elevated only among those who switched shifts (days to nonstandard HR 2.18, 95% CI 1.35–3.51; nonstandard to days HR 2.38, 95% CI 1.41–3.95). The only significant difference between men and women were among nonstandard shift workers. Conclusions Our results suggest that changing shift types may increase work injury risk among men and women, and that the risk remains increased among women who work nonstandard shifts for a prolonged period of time. This highlights the need for awareness and implementation of health and safety programs when workers initially change shift schedules and on a regular basis to maintain worker health."

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