The Hidden Toll: Secondary Health Consequences of Natural Disasters in Japan - A Systematic Analysis of 1,557 Studies

Introduction: While disasters directly claim many lives, secondary health effects among disaster-affected populations can be equally lethal. This scoping review aimed to map scientific evidence regarding secondary health effects following natural disasters in Japan. Methods: A systematic search was conducted using five databases: MEDLINE, CINAHL, EMBASE, PsychINFO, and Ichushi Web. Primary screening was performed independently by two blind reviewers who assessed titles and abstracts for inclusion. Descriptive statistical analysis was conducted on papers that passed secondary screening. Results: The database search yielded 16,870 papers, with 5,900 duplicates removed. Of the 10,970 papers screened, 1,557 met the inclusion criteria. The most frequently studied disasters were the Great East Japan Earthquake (n = 662, 42.5%), COVID-19 pandemic (n = 517, 33.2%), Great Hanshin-Awaji Earthquake (n = 102, 6.6%), Fukushima Daiichi Nuclear Accident (n = 90 papers, 5.8%), and Kumamoto Earthquake (n = 63, 4.0%). Predominant study designs included cross-sectional/observational studies (n = 660, 42.4%), follow-up studies (n = 490, 31.5%), survey research (n = 136, 8.7%), comparative studies (n = 102, 6.6%), and data analysis studies (n = 98, 6.3%). The most commonly investigated health conditions were psychiatric disorders (n = 824, 52.9%), followed by cardiovascular diseases (n = 163, 10.5%), health-related behaviors (n = 117, 7.5%), endocrine/metabolic disorders (n = 92, 5.9%), and respiratory diseases (n = 77, 4.9%). Conclusion: This scoping review captured a comprehensive overview of health effects following natural disasters in Japan, providing valuable insights into the patterns and distribution of secondary health impacts in disaster-affected populations.