Many people believe that the timing of your birth can affect your personality and even your fate. While astrology has been (mostly) debunked, several new studies have come to a surprising conclusion: The time of year in which you are born may have permanent effects on your health. According to this research, your season of birth affects mortality and other aspects of your health throughout your life.

Realities of Health and Your Season of Birth

Many cultures have beliefs related to how the timing of your birth can affect you. You may have heard the term “my sweet summer child,” which refers to the idea that an infant born in summer has yet to experience hardship. Most of this lore focuses on the fact that babies born in winter, a time of illness and hardship, are more likely to become ill from the challenges of the cold and dark months.

Prior research has suggested that winter babies indeed face unique health challenges. They are more likely to die of SIDS, a terrible event in which infants die suddenly of an unknown cause. Experts attribute this to the fact that babies are more likely to be wrapped in extra blankets or clothing in the colder months.

In addition, babies who are still small in the winter and early spring months are at higher risk of dying of RSV, a virus that causes serious respiratory symptoms in infants who have not yet developed mature immune systems.

The risks to winter babies are easy to comprehend. However, new studies are showing that the timing of your birth can have long-term effects on your health and your chances of living a long life.

How Your Season of Birth Affects Mortality

The Nurses’ Health Study began in the seventies and is one of the largest health studies to date, collecting data on the health and lifestyles of more than 100,000 nurses from all over the United States. Because this study collects a great deal of socioeconomic data, researchers can control for factors such as social class.

This was one of the first studies to find a link between the month of birth and mortality. Although it did not find a link between general mortality and birth timing, it did find a link between birth month and the chances of death from cardiovascular events. Specifically, people born in December appeared to have a lower chance of cardiovascular-related death.

This study introduces an interesting question: How can your month of birth affect your heart health decades later? Is this trend true for people in other occupations or in other countries?

A more recent study looked at Swedish people between the ages of 50 and 80 years old and different causes of death. People born in the spring were more likely to die of cardiovascular disease, while those born in September had a higher risk of dying of infections. Altogether, people born in November and December — the opposite of the proverbial sweet summer child — were the least likely to die of any cause.

Do Autumn Babies Live Longer?

How does this trend bear out over different geographic areas? A new study may answer this question. This study is ground-breaking because it used people from all over the world, including the Southern Hemisphere, as subjects. According to this new research, the season of birth can affect the health and ultimately the lifespan of people throughout the globe. Older people who were born in autumn live longer than people who were born in spring. This fact remains true in all regions of the world.

Although the reason for this link is not clear, many researchers believe that it may have something to do with the effects of vitamin D. Vitamin D is made in our skin cells when they are exposed to sunlight. Because it can be stored for several months at a time, babies born in late autumn have the most vitamin D while those born in spring are at high risk of deficiency.

Vitamin D is important for human health, but especially so for pregnant women. Pregnant women who have high vitamin D levels have a much lower chance of complications, which in turn leads to healthier babies. This little boost in the prenatal environment and birth may add up to dramatic effects over a lifetime.

What does this mean for those of us born in the spring? Although this research suggests that you are at higher risk due to your birth timing, there are many factors that contribute to your health and ultimately to your chances of living a long life. Eating healthy, getting enough exercise and getting plenty of sleep are still important choices that help to balance out a variety of other factors.