Have you ever wondered how old you’ll be when you die? Life expectancy represents the average number of years that someone can expect to live depending on the year they were born. For anyone born in the United States in 2017, life expectancy is 78.6 years, according to the Centers for Disease Control and Prevention (CDC).
Another way that experts measure life expectancy involves considering the percentage of people who live to specified ages. Using that approach, in 2017 nearly 25 out of 100 people in the United States lived to celebrate their 90th birthday, according to the CDC.
Both those calculations are based on averages of the entire population and include all sexes, races, and parts of the country. How long each individual lives is determined by many factors, says Qi Sun, MD, a doctor of science and an associate professor at the Harvard T.H. Chan School of Public Health. He explains that life expectancy is influenced by genes, environment, and lifestyle choices: “We can look at how the life span has increased over the last 100 years and see that it’s modifiable,” he says.
Family history is a big predictor of longevity. “If you look at parents’ life span and compare it with their offsprings’, you’ll find certain correlations because sometimes they share the same genes,” says Dr. Sun. If some of those genes lead to certain diseases, it may shorten life span. “On the other hand,” he adds, “families that have good genes may live longer.”
Some similarities in health patterns that may seem genetic could also be due to common habits and location. Family members often share the same environment, especially when children are young and still live at home. “Families eat a similar diet and have the same access to medical care, which are both factors that impact longevity,” Sun says.
women live longer than men
Women tend to live longer than men, and that’s been the case for at least the past century, says Robert Anderson, PhD, chief of the mortality statistics branch of the CDC. “Before that, a very high maternal mortality pulled down the average life expectancy for women,” he says.
Is U.S. life expectancy increasing?
The long-term increase in life expectancy over the past century is largely due to two factors. “From 1900 until 1950 and then from 1950 to 2000, there was a fairly dramatic increase in life expectancy, primarily due to control of infectious diseases,” says Anderson, citing significant discoveries in antibiotics and vaccines and improvements in sanitation.
Since 1950, gains in longevity are mostly due to advances in the prevention and treatment of chronic diseases, mainly heart disease and stroke. “There’s also been an improvement in the cancer death rates beginning in the mid-1990s,” Anderson says. Cardiovascular disease and cancer are the two leading causes of death in the United States, accounting for about 40 percent of total deaths.
Life expectancy has actually declined slightly over the past three years, according to the CDC. Although the CDC says the trend is largely driven by drug overdose and suicide, there is another, more significant factor: the obesity epidemic.
“I think it’s fair to say that we are already seeing the impact of obesity on life expectancy,” Sun says. “A lot of people out there blamed the opioid crisis or drug overdose for the decrease in life expectancy, but the obesity problem is much bigger.”
the most important factors
“Basically any factor that influences mortality also contributes to life expectancy, because mortality is how life expectancy is calculated,” says Sun. Blood pressure, cholesterol levels, body mass index, and diabetes are established risk factors for chronic diseases like heart disease and stroke, and people who have those diseases have a shorter life expectancy.
the healthiest lifestyle
“It’s never too late to adopt a healthier lifestyle,” says Sun. If a person has spent decades eating an unhealthy diet or being physically inactive, they may or may not have developed certain chronic conditions like diabetes or heart disease. Still, “If those individuals move their diet and exercise habits from the unhealthier end of the spectrum to the healthier side, they can improve their life span,” Sun says. “Just follow common sense: no smoking, avoid alcohol or drug abuse, eat a healthy diet, engage in physical activity, ensure proper healthcare coverage, and try to stay positive and optimistic.”
If you need more incentive to make lifestyle changes, consider this: Research shows that older adults are enjoying themselves more than just about everyone else. According to a survey of 1,546 Californians ages 21 to 99, people in their nineties were the most content. The research, published in August 2016 in The Journal of Clinical Psychiatry, found that older people were happier and less depressed, and had less anxiety than younger people.