Significant Association of House Collapse With High Urine Na/K Ratios Among 24,580 Coastal Residents Who Survived the Great East Japan Earthquake

Introduction: There is an association between dietary sodium/potassium intake and the pathogenesis of hypertension and cardiovascular disease. Some reports have indicated a correlation between psychological distress and high sodium intake. Victims who are affected by natural disasters tend to consume an unbalanced diet, with high sodium and low potassium levels, which may stem partly from high psychological distress due to natural disasters. Hypothesis: We tested the hypothesis that house collapse was associated with high urine Na/K (UNa/K) ratios in victims of the Great East Japan Earthquake. We also hypothesized that psychological distress could modify the relationship between house collapse and UNa/K ratio. Methods: We analyzed complete data collected from 24,580 coastal residents who did not take anti-hypertensive medications, were 20 to 74 years of age, and were enrolled in the Tohoku Medical Megabank Project Community-based Cohort (TMM CommCohort) Study. Participants were recruited between 2013 and 2015 at municipality-specific health checkup sites in the Iwate and Miyagi Prefectures. UNa/K ratios were assessed using spot urine samples. Participants were classified into four groups according to the extent of house collapse: total collapse (TC, n=4206); half collapse (HC, n=2825); partial collapse (PC, n=5964); and no damage (ND, n=11585). Using a covariance analysis, the multivariate-adjusted geometric means of the UNa/K ratios according to the group of house collapse were calculated, with adjustments for sex, age, systolic blood pressure, estimated glomerular filtration rate, HbA1c level, low-density lipoprotein cholesterol level, Kessler Psychological Distress Scale (K6) score, current alcohol consumption, current smoking habits, and daily exercise. In addition, after stratification according to K6 score (9/10), the multivariate-adjusted geometric means of the Una/K ratios were calculated according to house collapse group. Results: The multivariate-adjusted geometric means (95% confidence intervals) of UNa/K ratios of those whose houses underwent TC, HC, and PC were 3.33 (3.28-3.39), 3.37 (3.30-3.44), and 3.34 (3.30-3.40), respectively, all of which were significantly greater than the value of 3.23 (3.20-3.27) that was observed for the ND group. In analysis stratified by K6 score, the same tendencies were observed in both groups of K6<10 and K6≥10. Conclusions: House collapse was significantly associated with high UNa/K ratios, and psychological distress did not modify this association.