Janitors' mental workload, psychosocial factors, physical fitness, and injury: The SWEEP study

Approximately 2.4 million janitors work in the United States. High physical workload may explain a lost-work days rate 2.7 times that of other occupations. Information is limited about non-physical workload factors for janitors and their relations to injuries. For this retrospective cross-sectional study, specially designed, pre-tested questionnaires were distributed to full-time janitor members of a union for two six-month sequential intervals. Questions addressed mental workload (modified NASA Task Load Index), job satisfaction (Andrews and Withey Job Satisfaction Scale), stress (Perceived Stress Scale-4 [PSS-4], and the Single Item Stress Scale [SISS]), physical fitness, and occupational injury experiences. Descriptive and multivariable analyses, with bias adjustment, were conducted. A decreased risk of injury was associated with increased job satisfaction (expressed as a risk ratio (RR): 0.91 [95% confidence interval (CI): 0.83, 0.97]) and increased physical fitness (0.89, [0.83, 0.96]). A highly suggestive increased risk of injury was associated with increased mental workload (1.07, [1.00, 1.15]).