The ever-changing social implications of the COVID-19 pandemic have resulted in an urgent need to understand the working environments and health status of workers. We conducted a nationwide Internet-based health survey in Japanese workers in December 2020, in the midst the country's "third wave" of COVID-19 infection. Of 33,087 surveys collected, 6,051 were determined to have invalid responses. The 27,036 surveys included in the study were balanced in terms of geographical area, participant sex, and type of work, according to the sampling plan. Men were more likely than women to have telecommuted, while women were more likely to have resigned since April 2020. Moreover, 40% and 9.1% of respondents had a K6 score of 5 or higher and 13 or higher, respectively, they did not exhibit extremely poor health. The present study describes the protocol used to conduct an Internet-based health survey in workers and a summary of its results during a period when COVID-19 was spreading rapidly in Japan. In the future, we plan to use this survey to examine the impact of COVID-19 on workers' work styles and health.

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Background Two major definitions exist for presenteeism: sickness presenteeism and impaired work function. The evidence for comparing previous studies on presenteeism is insufficient because of the different definitions of presenteeism used. Aims To assess the relationship between the two major definitions of presenteeism. Methods This cross-sectional study analysed secondary data on 5334 respondents to an employee survey administered in a construction company in Japan. Impaired work function was measured using the Work Functioning Impairment Scale (WFun). Multiple logistic regression was performed. Results A strong linear association was observed between the number of days of sickness presenteeism and impaired work function (all P < 0.001). In contrast, the number of days of sickness absence was only partially positively associated with impaired work function. All choices for most frequent health problem were positively associated with impaired work function, beginning with mental problems (adjusted odds ratio [OR] = 20.45, 95% confidence interval [CI]: 14.94–28.01), followed by malaise (adjusted OR = 11.91, 95% CI: 9.08–15.62) and sleeping problems (adjusted OR = 8.62, 95% CI: 6.57–11.33). Conclusions A strong relationship was observed between the two major definitions of presenteeism, even after adjusting for a variety of chronic health conditions. Although a consensus on the definition of presenteeism is yet to be reached, this study provides insight on comparing existing studies on presenteeism.