Variation of mortality rate during the individual annual cycle

The month of birth was significantly associated with the month of death in 102,265 individuals who died in Kiev during the period 1990-2000. A consistent trend in deaths was revealed, with an excess around the birthday. This excess on the actual anniversary of birth was 44.4% in men (chi2=11.48, P<0.001) and 36.2% in women (chi2=7.64, P<0.01) over the expected value. Significant variations in the mortality rate were obtained, according to the month of the individual annual cycle (IAC). The excess of mortality has been associated with the first and the last months of IAC in different age groups as well as for all major causes of death: circulatory (heart and cerebrovascular) diseases, malignant neoplasms and violent death. Neither the emotional stress nor the behavioral changes associated with the birthday can explain the results obtained. We hypothesize that 'birth stress' might be imprinted in a structure of the biological rhythms of the organism, thus resulting in periodic changes of vulnerability and survivability during the course of the IAC.