Month of birth and survival to age 105+: Evidence from the age validation study of German semi-supercentenarians

Using data from Germany, we examine if month of birth influences survival up to age 105. Since age reporting at the highest ages is notoriously unreliable we draw on age-validated information from a huge age validation project of 1487 alleged German semi-supercentenarians aged 105+. We use month of birth as an exogenous indicator for seasonal changes in the environment around the time of birth. We find that the seasonal distribution of birth dates changes with age. For 925 age-validated semi-supercentenarians the seasonality is more pronounced than at the time of their birth (1880-1900). Among the December-born the relative risk of survival from birth to age 105+is 16% higher than the average, among the June-born, 23% lower. The month-of-birth pattern in the survival risk of the German semi-supercentenarians resembles closely the month-of-birth pattern in remaining life expectancy at age 50 in Denmark.