Association of habitual exercise with adults' mental health following the Fukushima Daiichi nuclear power plant accident: the Fukushima Health Management Survey

Introduction: The Great East Japan Earthquake and the Fukushima Daiichi nuclear power plant accident in March 2011 impacted survivors' mental health. This study examined whether exercise habits and mental health conditions were associated, and whether the degree of the effect varied depending on time. Methods: A self-administered questionnaire was sent annually to former residents (born before April 1, 1998) in registered evacuation areas. Exercise habit was evaluated by participants' exercise frequency, and responses were categorized into "almost never," "once a week," and "twice a week and more." Data were tracked during three periods: fiscal year (FY) 2011-2012, 2012-2013, and 2013-2014. The association between baseline habitual exercise and new onset of psychological distress was assessed using the Japanese version of the Kessler 6-item Psychological Distress Scale and logistic regression analysis. Results: A total of 1304 (5.7%) of 22,741, 1060 (4.7%) of 22,709, and 759 (3.6%) of 21,220 respondents had psychological distress in FY 2011-2012, 2012-2013, and 2013-2014, respectively. An association between exercise and psychological distress was observed in men in FY 2011-2012 (P for trend: 0.010) and in women in FY 2013-2014 (P for trend: 0.026). "Almost never" was associated with onset of psychological distress in men in FY 2011-2012 [odds ratio (OR): 1.317, 95% confidence interval (CI): 1.054-1.645] and in women in FY 2013-2014 (OR: 1.296, 95% CI: 1.027-1.636). Conclusions: Exercise habit was associated with psychological distress, and its effect in time varied according to sex.