OBJECTIVES: The high labour load is continuously considered problematic in Japan. Although several legal regulations have been introduced by the Ministry of Health, Labour and Welfare (MHLW), the mental health and the productivity in the labour environment are far from improved. We examined the impact of labour load and mental stress on productivity loss during the busiest weeks in a Japanese domestic market research company.

METHODS: The survey of mental stress and productivity loss were conducted on 259 workers with informed consents from 20/12/2017 to 12/1/2018. The questionnaires included Japanese Occupational Stress Questionnaire (JOSQ), which all companies are legally required to conduct for monitoring each worker’s mental health, Kessler 6 Mental Health Scale (K6), Holmes' Social Readjustment Rating Scale (SRRS), and Work Productivity and Activity Impairment Questionnaire: General Health V2.0 (WPAI-GH). Using an exploratory factorial analysis of scores of JOSQ, K6, and SRRS identified three stress-associated factors. The work time length of each participant during November to December 2017 was extracted from the company’s database.

RESULTS: The median K6 score was higher in twenties than in fifties (five-points and two-points, respectively) (p=0.047), which indicated higher mental stress in twenties. The work productivity loss due to health problem estimated based on WPAI-GH was significantly higher in twenties than in forties (50% and 20%, respectively) (p=0.001). The result of a multivariate generalized-linear model after a model selection showed that the work productivity loss was significantly higher in females, twenties, and participants with a depressive tendency factor, extroversion, neuroticism, or openness personality, or high work load in November 2017.

CONCLUSIONS: Youngest workers showed highest mental stress and largest productivity loss in the busiest season. The youngest generation who holds generally greater potential in the company is considered most exhausted in our study, which indicates a major issue for the working environment of Japanese companies.