Scientists share one easy swap you can start doing today that could help you live longer

• People who watch lots of TV are more likely to be unhealthy as they age, a study found.
• But swapping just an hour of TV for a walk could help you age better, the scientists said.

Watching less TV might help you live longer, new research suggests.

Researchers from the Harvard T. Chan School of Public Health investigated how sedentary behavior and light physical activity affected people's chances of aging healthily.

By 2050, 20% of the world's population is projected to be over 65, the researchers said. With this in mind, they wanted to identify lifestyle factors that could help people avoid problems associated with aging, such as chronic illnesses, cognitive decline, and physical limitations. The researchers defined healthy aging as being free of chronic diseases and problems with physical function, memory, or mental health at age 70.

The study was published in the journal JAMA Network Open on Tuesday. It used data collected across 20 years from 45,176 female participants of the Nurses' Health Study, an investigation into the risk factors of chronic diseases in women. Researchers compared the time participants spent watching TV and doing physical activity in an average week.

The team found that those who spent more time watching TV were less likely to age healthily. For every two hours participants spent watching TV, their odds of healthy aging decreased by 12%.

But the more time participants spent doing physical activity, the higher their odds of aging healthily. Every two hours of walking or standing they did each day was linked to a 12% higher chance of aging healthily. And the more intense the physical activity, the more their odds increased.

Even just replacing one hour of being sedentary while watching TV with one hour of moderate-to-vigorous physical activity — such as walking at a normal pace — each day was associated with 28% higher odds of healthy aging.

Watching less TV and walking more could help you live longer

From the study's findings, researchers identified four lifestyle factors that could help people become healthy: watching less than three hours of TV a day, walking or standing for at least three hours a day, doing at least 30 minutes a day of more intense activity like walking at a normal pace, and not being overweight.

They also found that participants who slept for fewer than seven hours each night could improve their odds of healthy aging by replacing TV time with sleep.

It's important to note that the findings of this study are not causal, meaning that researchers can't say for sure that watching TV causes unhealthy aging. But the researchers pointed out that sitting for long periods has been linked to reduced insulin sensitivity, increased inflammation, and reduced blood flow to the brain, while sitting in front of the TV specifically has been associated with unhealthy eating patterns, including overeating, which increases the risk of disease.

Since the study was done on a cohort of US nurses, the findings may not be the same for other demographics, the researchers added.

Professor Dan Belsky, an epidemiologist at the Robert N. Butler Columbia Aging Center, told Business Insider that this study "contributes additional data" to findings that have been known for a long time, that "people who report being more active also report better health outcomes."

He said: "What is needed now are studies to identify community- and society-level strategies that enable more people to be more active."