Introduction Nightshift work is prevalent in developed and developing countries in which female nightshift workers are more vulnerable, particularly for mental health.

Objective This study aims to investigate if the prevalence of negative emotion differ among male and female nightshift workers and explore the contributing factors using the baseline information of a prospective nightshift worker cohort in Shenzhen, China.

Methods We recruited 5329 workers and collected their blood/urine samples from 5 industries at the baseline, but only included 834 workers from 2 companies into this report because other 3 companies mainly composed of male workers. We adopted a standardized questionnaire to collect information on lifetime nightshift work, lifestyle factors, housework demands and socio-demographic data.

Results Overall, 510 workers were males (61.2%) and 324 were females (38.8%). More female than male workers were nightshift workers (90.1% vs. 82.7%), aged≥40 years (20.4% vs. 12.9%) and married (74.4% vs. 58.2%) but less females attained college or above (8.6% vs. 23.5%) and leisure-time exercises (32.7% vs. 50.0%). Significantly more female workers did different housework including cooking (12.7% vs. 9.6%), washing (50.6% vs. 31.4%) and taking care of children/elderly (20.4% vs. 12.2%), and the sex difference in housework demands was particularly prominent among nightshift workers. Female nightshift workers were more prone to negative emotion because of ‘feel exhaust or insufficient energy (40.1% vs. 32.2%)’, ‘worry of significant change of body weight (18.5% vs. 12.6%)’, ‘insomnia/poor sleep (31.5% vs. 21.3%)’, and ‘hard to concentration or forgetful (30.1% vs. 20.4%)’; however, there was no significant sex difference of negative emotion among daytime workers.

Conclusion This study reveals that female nightshift workers were more vulnerable to negative emotion, and nightshift work schedule and high housework burden are the contributing factors.