Background: The present study was to demonstrate the prospective association of workaholism (i.e., work excessively hard in a compulsive fashion) with sleep quality among Japanese employees. Methods: A web-based prospective survey was conducted in October 2010 and May 2011 among registered monitors of a survey company. The questionnaire included workaholism, sleep quality, job characteristics, and demographics. For the first-wave survey, a total of 13,564 monitors were randomly invited. The first 2,520 respondents were included in this study. The respondents of the first-wave survey were invited to the second-wave survey and 2,061 answered. A total of 364 respondents who had the changes in their working conditions during follow-up were excluded. Due to missing values, data from 14 respondents were excluded. Thus, the final number of respondents for the analysis was 1683 (859 males and 824 females). Analysis of covariance (ANCOVA) was conducted to compare adjusted sleep quality at follow-up among workaholism groups (low, middle, and high). In ANCOVA, demographics, sleep quality at baseline, and job characteristics were adjusted. Results: High-workaholic group had significantly longer sleep latency at follow-up compared to low- and middle-workaholic groups after adjusting for demographics, sleep latency at baseline, and job characteristics. Additionally, high-workaholic group had significantly higher levels of daytime dysfunction compared to low-workaholic group. However, no significant differences were found between workaholic groups in overall sleep quality, sleep duration, habitual sleep efficiency, sleep disturbance, and use of sleep medication. Conclusion: Workaholism is associated with poor sleep quality at seven-month follow-up regarding sleep latency and daytime dysfunction.

本研究は、日本国内の労働者を対象として、ワーカホリズム (強迫的かつ過度に一生懸命働く傾向) が睡眠の質 (全般的な睡眠の質、入眠時間、睡眠時間、睡眠効率、睡眠障害、眠剤の使用、日中覚醒困難) に与える影響を検証することを目的に、国内のA調査会社に登録しているモニタを対象とした前向きコホート調査を2010年10月(ベースライン)と2011年5月(フォローアップ) に実施したものであり、以下の結果を得ている。

1. 入眠時間に関して、ワーカホリズム低群および中群と比べ、ワーカホリズム高群において全ての共変量(属性、ベースラインでの入眠時間、仕事関連要因)投入後もフォローアップ時点の入眠時間が有意に長いことが明らかになった。

2. 日中覚醒困難に関して、ワーカホリズム低群と比べ、ワーカホリズム高群において全ての共変量を投入後もフォローアップ時点の日中覚醒状態が有意に悪いことが明らかになった。

3.全般的な睡眠の質、 睡眠時間、睡眠効率、 睡眠障害、眠剤の使用、に関しては全ての共変量を投入後のワーカホリズム群間で有意な差は認められなかった。

以上、本論文はベースライン時のワーカホリズムが 7ヶ月後の睡眠時間および 日中覚醒困難に関して悪影響を及ぼすことが明らかにした。本研究はこれまで知見の少なかった、ワーカホリズムが睡眠の質に及ぼす長期的な影響を示唆するものであり、産業精神保健領域における重要な貢献をなすと考えられ、学位の授与に値するものと考えられる。