Inactive over-65s who took up weekly exercise had fewer walking problems two years later

Being able to walk a few blocks or climb a flight of stairs is one of the things that keeps older people independent. It is well known that active older adults tend to keep this ability longer. A harder question is whether it helps to start being active late in life, after years of doing very little.

A new analysis of a large US survey suggests it might. Among people over 65 who had been inactive for years, those who began moderate or vigorous activity at least once a week were less likely to report new trouble with walking or stairs about two years later. The study is a preprint, not yet peer-reviewed, and it is observational: people chose for themselves whether to become active.

What they did

The data come from the Health and Retirement Study, a long-running US survey of people over 50, conducted by the University of Michigan, which interviews the same people every two years. People were asked how often they did moderate and vigorous physical activity. Here, "regular activity" meant either kind at least once a week.

The analysis used target trial emulation: it set out the rules of an imagined randomized trial and then mimicked it with the survey data. Eligible were people aged 65 or over who had reported no regular activity at two interviews in a row and who had no difficulty with walking, stairs or everyday tasks such as dressing, bathing, shopping or managing money. At the next interview, those who now reported regular activity were counted as "initiators"; those still inactive were "noninitiators". Because a person could be inactive at one interview and start being active at a later one, the same person could enter the analysis more than once. There were 1,037 such entries from 765 people: 377 initiators and 660 noninitiators.

To make the two groups comparable, the analysis gave more or less weight to each person based on age, sex, income, wealth, education, self-rated health, weight, smoking, chronic illnesses and earlier activity. The main outcome was a first report of difficulty with walking a block or more or climbing stairs.

What they found

• At about 2 years: 32.75% of initiators had developed mobility difficulty, against 39.73% of noninitiators, a difference of about 7 percentage points. This was the only time point where the gap was statistically significant.
• At about 4 and 6 years: initiators still fared a little better (50.27% vs 53.17%, and 59.52% vs 64.96%), but the ranges of uncertainty included no difference at all.
• Everyday tasks: there was no clear difference in new difficulty with self-care (such as dressing or bathing) or with household tasks (such as shopping or cooking).
• Checks: three other ways of running the analysis gave similar results at two years.

What to keep in mind

• Not randomized. The study itself notes that people who start exercising may differ from those who don't, in motivation or underlying health, in ways the survey doesn't capture. The weighting only balances what was measured.
• Rough measure of activity. Activity was self-reported as how often, not how long or how much. So "regular activity" here does not mean meeting the official activity guidelines.
• Unknown timing. Interviews were two years apart, so the exact moment someone started being active, or first had trouble walking, is unknown.
• Starting is not sticking. People were grouped by what they did at one interview. Some initiators may have stopped later and some noninitiators may have started, which could explain why the gap narrowed over time.
• Modest numbers. With 377 initiator entries, the estimates are fairly imprecise, especially at later time points.
• Self-reported outcomes. Difficulties were reported by the participants, not measured.

Why it matters

The result fits with a well-known randomized trial cited in the paper, the LIFE study, in which a structured exercise programme reduced major mobility disability in sedentary older adults at risk of disability. This new analysis looks instead at people who started being active on their own, in ordinary life, after years of inactivity, and suggests that the change was linked to fewer walking problems in the following two years. Whether the benefit lasts, and how much activity is needed, are questions the study cannot answer; it calls for more detailed data on when people start and how long they keep going.