Differential underestimation of work-related reinjury risk for older workers: challenges to producing accurate rate estimates

Background: Older workers are increasingly represented in the U.S. workforce, but frequently work part-timeor intermittently, hindering accurate injury rate estimates. To reduce the impact of reporting barriers on rate comparisons, we focused on reinjury (both injury recurrence and new injury) among workers with a workers' compensation claim, assessing: (1) reinjury risk for workers age 65+ versus <65; (2) importance of work-time at-risk measurement for rate estimates and comparisons; and (3) age distribution of potential risk factors. Methods: Washington State workers' compensation claims for a retrospective cohort of workers with work-related permanent impairments were linked to state wage files. Reinjury rates were calculated for the cohort (N = 11,184) and a survey sample (N = 582), using both calendar time and full-time equivalent (FTE)-adjusted time. Risk differentials were assessed using rate ratios and adjusted survival models. Results: The rate ratio for workers age 65+ (vs. <65) was 0.45 (p < 0.001) using calendar time, but 0.70 (p = 0.07) using FTE-adjusted time. Survey-based rates were 35.7 per 100 worker-years for workers age 65+, versus 14.8 for <65. Workers age 65+ (vs. <65) were more likely to work <100% FTE, but were similar regarding job strain, their ability to handle physical job demands, and their comfort reporting unsafe conditions or injuries. Conclusions: Accounting for work-time at risk substantially improves age-based reinjury comparisons. Although the marked elevation in self-reported reinjury risk for older workers might be a small-sample artifact (n = 34), workers age 65+ are likely at higher risk than previously appreciated. Ongoing workforce trends demand increased attention to injury surveillance and prevention for older workers.