Understanding Life Expectancy

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Life expectancy refers to the average number of years an individual is expected to live. It can be affected by that person's family and health history, genetics, environment, lifestyle factors such as diet, and even age and sex.

Life expectancy also can refer to the average number of years a group of people or a specific population is expected to live. Whether referring to an individual or a group, the most common measure of life expectancy is life expectancy at birth, which is the age to which a newborn is expected to live given age-specific death rates at the time of their birth.

For example, according to the Centers for Disease Control and Prevention (CDC), the life expectancy at birth of a person born in 2017 is 78.6 years. However, as mentioned, life expectancy can be affected by certain factors. Take sex, for example: The life expectancy at birth of a male baby born in 2017 is 76.1 years, while that of a female newborn is 81.1 years.

Changes in Life Expectancy

Life expectancy can change. Deaths at young ages impact life expectancy averages much more than deaths at older ages. Young deaths impact life expectancy at birth statistics. 

Each year a person lives means they have survived multiple potential causes of death. This means that life expectancy actually can increase with age. For instance, in 2006 the life expectancy at birth of someone born in 1942 was about 68 years. If that person survived to 65, they could expect to live another 18.4 years, meaning their life expectancy was no longer the same as it was at birth—it was 5.9 years longer than the life expectancy of people born in 2006—83.4 years.

If that person lived to 75, their life expectancy increased to 86.8—9.3 years longer than the average child born in 2006.

Beating the Odds

All the statistics in the world ultimately can't predict precisely how long a person will live. Although there are many factors that contribute to life expectancy that cannot be altered—again, sex, race, genetics—there are plenty of things they can do. Longevity can be affected by measures to preserve health, for example—eating nutritious food, maintaining a healthy weight, staying physically and mentally active, engaging in social opportunities, abstaining from smoking, drinking little or no alcohol.

Taking measures to stay safe can also play a role—wearing a seatbelt in a car, for example, or a helmet and other safety gear when engaging in sports.

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