Background The Irish population is ageing, and the number of people reaching their 100^th birthday is also increasing. Prior researched has found that that the spatial distributions of those living beyond 100 years are not random. We explored the prevalence of centenarians in Ireland and whether the distribution was concentrated in areas with common lifestyle and environmental factors.

Methods We used data from mortality.org to track the number of centenarians and those aged over 100 years in Ireland since the 1950s. We used 2011 census data collected by the Central Statistics Office to calculate age standardised rates of centenarians in each county, acknowledging differing age structures in each country which may confound estimates of prevalence. We retrieved census data on disposable income, marriage status, social class and highest level of education reached at the county level to help explain the profiles of counties.

Results Roscommon, Clare and Mayo emerged as the counties with the highest age standardised rates of centenarians with 379, 358 and 275 centenarians/100,000 population aged 70–79 years. Limerick, Wexford and Laois had the lowest rates with 78, 61 and 29 centenarians per 100,000 population aged 70–79 years. Income was not lower or higher in Roscommon, Clare and Mayo than in the three low rate counties. Similarly, there was no difference in highest level of education achieved or in social class. Roscommon had a high proportion of married couples (40.2%) in comparison to the low rate counties (approx 37.5% on average).

Conclusion Our analyses show a concentration of centenarians in rural counties in the west of Ireland. This is consistent with prior research locating “pockets” of centenarians in isolated areas where agriculture is dominant, food is sourced locally and a sense of community prevails. Our estimates of education, social class and affluence did not reveal any patterns that have been demonstrated in other areas. Our data were limited by their aggregate nature. Further analyses may seek to use individual level data with information on other variables associated with longevity such as BMI and smoking. The Irish Longitudinal Study of Ageing (TILDA) may provide opportunity to analyse further. Data on the ageing population are essential from a public health perspective in addition to planning concerns for the health services.