Occupational Consistency between Main and Side Jobs and Age-related Differences in Occupational Injuries or Diseases among Japanese Workers: A Nationwide Cross-Sectional Study.

Mori, Takahiro; Nagata, Tomohisa; Odagami, Kiminori; Mori, Koji · J Occup Environ Med · 2026

cross_sectional · Level IV

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Abstract

This study examined whether the risk of occupational injuries or diseases in the main job differs by side job type (same or different occupation) and by age. A cross-sectional online survey of 22,369 employed individuals was analyzed. Participants were classified as no side job, same-occupation, or different-occupation side job. Multilevel logistic regression analyses were conducted to estimate odds ratios (ORs). Compared with no side job, both same- and different-occupation side jobs were associated with higher risks (ORs = 1.69 and 1.89). This pattern was observed in younger and middle-aged workers, whereas among older workers the association was stronger for different-occupation side jobs (OR = 1.49). Engaging in side jobs was associated with increased safety risks among younger and middle-aged workers, whereas occupational mismatch warrants attention among older workers.