Study birth month affects life expectancy

Study by the University of Greifswald: The month of birth influences life expectancy

16/03/2011

Do people live longer because they were born in the month of May in November? The University of Greifswald reports on this strange connection on the basis of an evaluation of death data. Obviously, the birth month decides how high the relative life expectancy of a person is. So far, the scientists can only speculate about the exact correlations. The results of the meta-analysis could, however, make a significant contribution to improving the preventive measures of cardiac events.

November children live much longer
According to a scientific evaluation of the University of Greifswald November children live seven to eleven months longer than people who were born in, for example, in May. Relative life expectancy apparently depends on the month of birth and the season, according to the researchers. The scientists came to this conclusion by analyzing more than six million deaths in Germany caused by cardiovascular diseases. Those born in November lived a few months longer than any other birth month.

Results apply equally to women and men
The observation applies according to study results for both sexes alike. However, the study showed that the difference in men is even more apparent than in women. Male November children lived 11.7 months longer on average than their peers. Women born in November statistically lived 7.3 months longer than other seasons children.

For the study, the research team examined all Germany-wide deaths between 1992 and 2007. All mortalities examined showed as a result of death cardiovascular diseases such as a heart attack or stroke. The data came from two different sources. On the one hand, the researchers used existing death data from the Federal Statistical Office and, on the other hand, the results of the Research Data Center of the State Statistical Office in Saxony.

The researchers could rule out statistical randomness, as life expectancy rose continuously from May to November. November peaked in the life expectancy curve, after which life fell again. By no means does this hitherto unexplained phenomenon only refer to cardiovascular deaths. In order to secure the findings, the team also compared the data of other causes of death. Again, similar results could be observed.

No regional features
The data leave no doubt that there are special regional differences. The life curve is just as recognizable in southern Germany and northern Germany. There were also no differences in the comparison of East and West. Although the general life expectancy differs in the various federal states, the data always refer to the birth month curve.

Exact reasons of the influencing factors still unclear
Why the birth month affects the lifespan, about speculation can be made. The head of the research team, Dr. med. Thorsten Reffelmann: "At present, we can only speculate about the factors that have such a significant impact on cardiovascular risk in our first few months of life before or after birth." However, the scientist suspects that the intensity of the sun's rays, diet during pregnancy, pollution from environmental and air pollution or even infectious diseases could play a role. It is also possible that the nature and duration of physical stress and movements play a role during pregnancy. Because these are subject to strong fluctuations during the different seasons. Pregnant women move significantly less during the cold seasons than, for example, in spring. „In addition to meteorological data or sunlight exposure, many other factors are also conceivable. Food supply and nutritional habits in pregnancy, air pollution or infectious diseases in the course of a year or the extent of physical activity, which is also subject to seasonal fluctuations.“ explained Reffelmann.

Results significant for preventive cardiology medicine
The results are very important for preventive cardiology medicine, says Prof. Stephan Felix, Head of Greifswald Cardiology. It has long been suspected that the first stages of life, whether in the womb or shortly after birth, have a lasting impact on a variety of risks of serious illnesses such as heart attack, high blood pressure or stroke. The exact context needs to be followed by further research. The study results of the Center for Internal Medicine of the University of Greifswald were published in the American Science Magazine „Journal of the American College of Cardiology“ released.

Other studies indicate that stress, general well-being, as well as diet and lifestyle are very important factors in life expectancy. For example, a recent study by the University of Illinois found that "happiness" is an important factor in positively influencing life expectancy. A meta-analysis of over 160 studies found that positive emotions increase life expectancy and stress, in contrast, significantly weakens the immune system. (Sb)

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Picture: Alexandra H.