Incidence rates of medically certified long-term sickness absence among Japanese employees: A focus on sex differences.

Abstract

Background: Long-term sickness absence (LTSA) is an important public health challenge, yet limited data exist on its incidence in Japan. We aimed to describe the incidence of all-cause and cause-specific LTSA by sex and age, using 10-year data from a large Japanese working population, focusing on sex differences.

Methods: The study participants were employees from 16 worksites in the Japan Epidemiology Collaboration on Occupational Health Study between April 2012 and March 2022. LTSA, defined as sickness absence from work lasting 30 days or more, was recorded at each worksite. The causes of LTSA were classified using the International Classification of Diseases, 10th Revision. Incidence rates for all-cause and cause-specific LTSA were calculated based on sex and age.

Results: During 730,391 and 161,513 person-years of follow-up, 6,518 and 1,866 spells of LTSA were recorded in males and females, respectively. Females had higher incidence rates of all-cause LTSA than males (115.5 vs. 89.2 per 10,000 person-years), especially among females in their 20s and 30s. This was partly attributed to younger females experiencing higher LTSA incidence rates due to mental disorders, neoplasms, and pregnancy-related illnesses. In older age, females had higher LTSA incidence rates than males for musculoskeletal diseases and injuries/external causes, whereas LTSA incidence rates due to circulatory diseases were lower than those in males.

Conclusion: The incidence of total and cause-specific LTSA varied greatly by sex and age, highlighting the need to consider employees' characteristics in the prevention and management of LTSA.