The disruption of routine treatment, including the interruption of medication, exacerbates chronic conditions during disasters. However, the health consequences of the interruption of medication have not been fully examined. On 22 July 2006, a flash flood affected more than 3,000 households in five cities and four towns in the northern part of Kagoshima Prefecture in southwest Japan. The aims of this study are to describe the prevalence of the interruption of medication among the outpatients in the flood-affected area and to determine the risk and preventive factors for the interruption of medication.

This was a cross-sectional study using a self-administered questionnaire. The study subjects were the outpatients who visited nine of 15 medical facilities in the flood-affected area from 23 January and 31 January 2007. Of 810 valid respondents, 309 who received medication treatment before the event were eligible for the study. Information on socio-demographic factors, chronic health conditions, preparedness-related factors before the event and damage-related factors were collected. Overall and evacuation status-specific prevalence of interruption of medication were presented. For those evacuated, the associations between interruption of medication and relevant patient characteristics, as well as deterioration of health status after the event, were examined.

The prevalence of interruption of medication was 9% in total, but it increased up to 23% among the evacuated subjects. Interruption of medication was more likely among those aged ≥75 years (odds ratio [OR] = 3.6; 95% confidence interval [CI] = 1.0−12.6) and those receiving long-term care services (OR = 4.6; 95% CI = 1.1−19.1), while it was less likely among those with hypertension (OR = 0.2; 95% CI = 0.1−0.8) and those prepared to go out with medication (OR = 0.2; 95% CI = 0.03−0.8). Those who experienced interruption of medication were more likely to have deteriorated health status one month after the event (OR = 4.5; 95% CI = 1.2−17.6).

Interruption of medication occurred more commonly among the evacuated subjects. Among the evacuated, the elderly and those receiving longterm care services were at high risk for interruption of medication, while the preparedness behavior of “preparing to go out with medication” had preventive effect. Special attention must be paid to the high-risk subgroups, and some preventive behaviors should be recommended.