Objective To examine the hypothesis that disability prevalence has increased to a greater degree in the areas severely affected by the earthquake and tsunami of 11 March 2011 than in other areas.

Methods Longitudinal analysis using public statistics data from the Ministry of Health, Labour and Welfare in Japan. The analysis included 1549 municipalities covered by the Long-term Care Insurance (LTCI) system. ‘Disaster areas’ were defined as three prefectures (Iwate, Miyagi, Fukushima). The outcome measure was the number of aged people (≥65 years) with LTCI disability certification. Rates of change in disability prevalence from February 2011 to February 2012 were used as the primary outcome variable, and were compared by analysis of covariance between ‘Coastal disaster areas’, ‘Inland disaster areas’ and ‘Non-disaster areas’.

Results Regarding disability prevalence at all levels, the mean value of the increase rate in Coastal disaster areas (7.1%) was higher than in Inland disaster areas (3.7%) and Non-disaster areas (2.8%) (p<0.001).

Conclusions The areas that were severely affected by the earthquake and tsunami had a significantly higher increase in disability prevalence during the 1 year after the earthquake disaster than other areas.