THURSDAY, July 19 (HealthDay News) -- You may think of your birthday as only being important to your age and the possible presence of candles, cards and cake, but a new study suggests a link between your month of birth and longevity.
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Researchers found that those who were born between September and November from the years 1880 to 1895 were more likely to reach the 100-year mark than their siblings who were born in March. The study does not prove a cause-and-effect link, just an association.
The meaning of the findings is unclear, and a researcher who studies lifespan called them mostly irrelevant to modern times.
But, Leonid Gavrilov, from the Center on Aging at the University of Chicago, who wrote the study with his wife, Natalia Gavrilova, said the findings point to the importance of the environment in which a child is conceived and later grows.
"We believe that avoiding any potential sources of damage to developing fetus and child may have significant effects on health in later life and longevity," Gavrilov said. "Childhood living conditions may have long-lasting consequences for health in later life and longevity."
The researchers looked at 1,574 centenarians -- people who reached the age of 100 -- in the United States. They found that those people born between September and November had about a 40 percent higher chance of living to 100 than those born in March.
Of course, the chances that people born in 1889-1895 would even reach the century mark was very low to begin with. Of those born in 1900 who were still alive at 50, just a third of 1 percent of men made it to 100, and just shy of 2 percent of women accomplished the feat, Gavrilov said.
Why might month of birth -- or month of conception -- affect how long someone lives? One possibility is that seasonal diseases played a role, Gavrilov said.
S. Jay Olshansky, a professor of public health at the University of Illinois at Chicago who's familiar with the findings, said the study is not newsworthy. "The results are probably valid, but largely irrelevant in our modern world since they apply to birth months from more than a century ago."
Regardless of the month someone was born or conceived, the odds are slim that you'll live to be 100. "This prospect has been rising through the 20th century, but not dramatically," Olshansky said.
At best, he said, "this research might offer a partial and extremely small explanation for a small fraction of why some people conceived and born more than a century ago lived for 100 years."
What does all this mean for your chances of living to 100 if you were born around the fall or -- perhaps less luckily -- in March? Good question -- and one that won't be answered until people around your age start hitting the century mark.
The study appeared in the Journal of Aging Research.
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SOURCES: Leonid Gavrilov, Ph.D., research associate, Center on Aging, University of Chicago; S. Jay Olshansky, Ph.D., professor, public health, University of Illinois at Chicago; 2011 Journal of Aging Research