Background: Approximately 2.38 million janitors are employed in the U.S. While high physical workload may explain a lost-work days rate 2.7 times greater than other occupations, little is known about the association between janitors' physical workload, mental workload, and stress.
Objective: The objective of this study was to assess the associations between physical (ergonomic) and mental workload exposures and stress outcomes among janitors.
Methods: Questionnaire data, focused on ergonomic workload, mental workload and stress, were collected from Minnesota janitors for a one-year period. Physical workload was assessed with Borg Scales and Rapid Entire Body Assessments (REBA). Mental workload assessment utilized the NASA Task Load Index (TLX). Stress assessments utilized single-item ordinal stress scale (SISS) and Perceived Stress Scale-4 (PSS-4) measures. Descriptive and multivariable analyses, including bias adjustment, were conducted.
Results: Odds ratios (OR) and 95% confidence intervals (CI) for ergonomic workload (task frequency) effects on SISS were: REBA (1.18 OR, 1.02-1.37 CI); Borg (1.25 OR, 1.00-1.56 CI); combined REBA and Borg (1.10 OR, 1.01-1.20 CI). Mental workload was associated with higher PSS-4 levels (0.15 Mean Difference, 0.08-0.22 CI) and a 3% increased risk for each one-unit increase in the SISS scale (1.03 OR, 1.02-1.05 CI).
Conclusions: This research demonstrated a moderate effect of physical and mental workloads on stress among janitors.
Keywords: Ergonomics; NASA TLX; Perceived Stress Scale; injury epidemiology.