**Background:** The Great East Japan Earthquake (GEJE) of March 11, 2011, caused approximately 19,000 deaths and displaced over 400,000 survivors, with older adults (≥65 years) accounting for over 20% of evacuees. Older adults are particularly vulnerable to disasters due to impaired mobility, chronic health problems, and social isolation. Previous studies on earthquake-related mortality were limited in geographic scope and causes of death examined. This study aimed to investigate the 3-year impact of the GEJE on mortality from five major causes (neoplasm, heart disease, stroke, pneumonia, and senility) among older adults in the three most severely affected prefectures (Fukushima, Miyagi, Iwate) compared with the other 44 prefectures in Japan.
**Methods:** This retrospective study used population-based death certificate data from 2006 to 2015, obtained from the Ministry of Health, Labour and Welfare of Japan. From 12,092,057 death certificates, exclusions were made for foreign nationality, unknown age, and mismatched registration years, yielding 11,997,759 deaths. The analysis focused on 7,383,253 deaths among adults ≥65 years from the five specified causes (senility analysis excluded ages 65–74 due to limited deaths, leaving 7,379,295 deaths). Causes were identified using ICD-10 codes. Population data came from the National Cancer Center of Japan by 5-year age categories. Mortality rates (MRs) per 100,000 population were calculated by sex, age category (65–69 through ≥95 years), and prefecture. Linear mixed models (LMMs) with log-transformed MR as the response variable were used to estimate risk ratios (RRs) and 95% confidence intervals (CIs). Fixed effects included area category (Fukushima, Miyagi, Iwate, other 44 prefectures), year of death (2006–2015), age category, sex, and interaction terms between area category and each year from 2010 to 2013. A random intercept for all 47 prefectures was included. A p-value < 0.05 was considered significant. Analysis was performed using SAS 9.4.
**Key Results:** The mean annual population aged ≥65 years was 25.6% in Fukushima, 22.9% in Miyagi, 27.7% in Iwate, and 23.6% in other prefectures. Mean annual mortality rates for those ≥65 years were 3,862 (Fukushima), 3,610 (Miyagi), 3,836 (Iwate), and 3,575 (other prefectures) per 100,000. For the interaction terms (area × year), the RRs for stroke significantly increased only in Miyagi Prefecture in 2011 (RR 1.13; 95% CI, 1.01–1.27). For pneumonia, the RR significantly increased in Miyagi in 2011 (RR 1.17; 95% CI, 1.04–1.31), while significant decreases were observed in Miyagi (RR 0.86; 95% CI, 0.77–0.97) and Iwate (RR 0.88; 95% CI, 0.78–0.98) in 2013. For senility, the RR significantly increased only in Miyagi in 2011 (RR 1.28; 95% CI, 1.07–1.54) and significantly decreased in Fukushima in 2013. No significant increases were found for neoplasm or heart disease in any prefecture or year. The RRs for neoplasm ranged between 0.95 and 1.01 across affected prefectures from 2010 to 2013. For heart disease, RRs in 2011 were 1.06 (95% CI, 0.95–1.20) in Fukushima, 1.03 (95% CI, 0.91–1.15) in Miyagi, and 1.06 (95% CI, 0.95–1.20) in Iwate—none statistically significant.
**Clinical Implications:** The study demonstrates that the GEJE had a limited, single-year impact on cause-specific mortality among older adults, with significant increases observed only in Miyagi Prefecture for stroke, pneumonia, and senility in 2011. The lack of significant findings in Fukushima and Iwate suggests that factors beyond earthquake intensity—such as evacuation patterns, shelter conditions, and healthcare disruption—may mediate disaster-related mortality risk. The transient nature of the increased risk (2011 only) suggests that acute-phase interventions in the first year post-disaster may be most critical. The findings highlight the importance of blood pressure screening and management (disaster hypertension) for stroke prevention, proper shelter conditions and infection control for pneumonia prevention, and maintaining physical activity and cognitive engagement for older adults to prevent functional decline. The decreased RRs for pneumonia in 2013 in Miyagi and Iwate and for senility in Fukushima in 2013 remain unexplained and warrant further investigation. Limitations include the lack of individual-level data on evacuation status, comorbidities, and daily activity levels, as well as the inability to compare coastal versus inland areas within prefectures. P-values were not adjusted for multiple testing and should be interpreted as exploratory.