There's a lot to be said for a birthday in September, October, or November. You get to celebrate the occasion in crisp autumn weather, safe from the blazing heat of summer and the bitter cold of winter. More importantly, according to a new study from researchers at the University of Chicago, your autumn birthday might be your ticket to a longer life. Is the timing of your birth the key to longevity? Here, a brief guide:

Do people born in fall really live longer?
Well, it's no guarantee, but apparently it improves your odds of reaching really, really old age. The researchers studied the lives of more than 1,500 people who were born between 1880 and 1895 who lived to be 100 or older. They found that most of the people who enjoyed extraordinarily long lives had birthdays in September, October, or November. By contrast, a slight majority of people in the non-centenarian population were born in the first half of the year. In fact, three birth months — March, May, and July — had 40 percent fewer centenarians. The researchers then compared the centenarians' birth months to those of nearly 12,000 siblings and spouses. 

Why compare them with brothers, sisters, and spouses?
The idea, the researchers said in the Journal of Aging Research, was to judge the significance of the centenarians' birthdays, as opposed to their living conditions, in explaining their longevity. Looking at the data for siblings allowed the researchers to take into account conditions early in life, such as poverty vs. wealth, that might have played a role. Looking at husbands and wives covered the same ground regarding the subjects' living conditions when they were older.

So why do those born in fall live longer?
The researchers couldn't pinpoint an explanation, but they have a few theories. "Childhood living conditions may have long-lasting consequences for health in later life and longevity," says Leonid Gavrilov, one of the study authors. For example, in the late 19th century, when these men and women were born, their mothers might have had access to better nutrition at different times of the year. Similarly, seasonal infections might have affected fetuses in the womb, hitting those conceived in different months at significantly different points in their development. Also, the milder fall weather might have helped babies born then to grow up stronger by protecting them from extra stress. More research will be needed to confirm the various explanations... and to determine whether other factors, such as air-conditioning and modern medicine, have erased the apparent advantages of being born in the fall.

Sources: Discovery News, Journal of Aging Research, HealthDay