The study sheds light on the question of whether the slower mental and physical decline seen among active seniors extends to former couch potatoes who begin exercising later in life.
"Regular physical activity in older age is important to remain healthy. However, taking up physical activity at old age is also beneficial," Mark Hamer told Reuters Health in an email. He led the study at University College London.
These findings "underscore the importance of prevention as well as rehabilitation," said Ursula M. Staudinger, who directs the Robert N. Butler Columbia Aging Center in New York City.
"When you start later in life you can still get gains," Staudinger, who was not part of the research team, said.
For their study, Hamer and his coauthors analyzed information on 3,454 healthy seniors involved in the ongoing English Longitudinal Study of Ageing.
Participants reported how much they exercised at the start of the study, in 2002 to 2003. Researchers then followed them through regular health surveys for the next eight years.
At follow-up, 19 percent of the seniors were considered to be aging healthily. That is, they had not developed any major chronic diseases or depression and had not experienced any deterioration in their physical or mental status during the study period.
Seniors who were active at least once a week at the start of the study and remained active were the most likely to experience healthy aging. But those who started exercising during the study period benefited as well, Hamer and his colleagues reported in the British Journal of Sports Medicine.
People who remained active during all eight years were over seven times more likely to experience healthy aging than inactive seniors. Those who became active after the study started were three times more likely than inactive adults to age well.
That was after the researchers took into consideration other factors that might influence healthy aging like participants' gender, income and whether they smoked or were married.
"The results appear to suggest that maintaining or beginning any form of regular activity is beneficial," the researchers wrote. Further, they added, "this study supports public health initiatives designed to engage older adults in physical activity, even those who are of advanced age."
"The ageing population continues to grow," Hamer said. "Physical activity will help the elderly to remain healthy."
The findings cannot prove exercise warded off disease among study participants, just that it was correlated with healthy aging.
"We have to say goodbye to this notion that the chronological age on our passport or our birth certificate will tell us how old we are," Staudinger told Reuters Health.
"Healthy aging is happening on a societal level and each individual can contribute," she said, noting that "physical activity is one important instrument."
However, Staudinger cautioned, "with physical fitness as with cognitive fitness, if you stop working on it, it will drop again."