Introduction There is growing social concern about the expanding socioeconomic and health disparities that have occurred in Japan in the past 3 decades. We investigated if Japanese geographic and socioeconomic disparities in life expectancy at birth (LE) have widened in this period.

Methods We used data on the LE of municipalities calculated every 5 years between 1985 and 2005. The municipality is the smallest administrative unit, for which LE data are available. Sample sizes varied from 1963 to 3354 across years due to nationwide municipality mergers undertaken after 2000. We also gathered information on the unemployment rates and other socio-demographic characteristics of municipalities. We used the relative index of inequality (RII) of LE (which corresponds closely to the relative LE gap between the top vs bottom municipalities in terms of LE or socioeconomic status, accounting for the variations in population size across all municipalities).

Results Among men, in 1985, the LE gap was 4.2% when municipalities were ranked by LE and 1.6% when ranked by the unemployment rate (as ordered from the lowest to the highest). Among women, these gaps were 2.6% and 0.4%, respectively. These values changed only slightly over time, showing a tendency for a slight increase among men after 2000 and a decrease in women after 1995.

Conclusion In Japan, during the period 1985–2005 geographic and socioeconomic disparities in municipal LE were larger in men than women. However, the LE disparity has been relatively small and stable despite the increase in income inequality since the 1980s.