Nearly half of older adults get sharper or stronger with age, not weaker

The default assumption about aging is decline: memory gets a little worse, walking gets a little slower, every year a little less than the one before. A 12-year Yale study of the Health and Retirement Study — a large, federally funded survey of older Americans — found that assumption is true only on average, and badly misleading for any one individual.

What the study measured

Researchers followed more than 11,000 participants for up to 12 years, tracking two things geriatricians consider core indicators of overall health: global cognitive function and walking speed, the latter closely linked to disability, hospitalisation and mortality risk in the wider literature. Rather than only averaging scores across the group — which is where the "decline is inevitable" story comes from — the team tracked individual trajectories over time.

The result: 45% improved

Individually, 45% of participants showed a meaningful improvement in at least one of the two measures: 32% improved cognitively and 28% improved physically, with many gains large enough to be clinically significant. Counting people who simply held steady rather than declined, more than half avoided the commonly assumed trajectory of continuous cognitive deterioration. Crucially, these gains were not confined to people who started out impaired and were merely recovering — participants with normal baseline function improved too.

"What’s striking is that these gains disappear when you only look at averages. If you average everyone together, you see decline. But when you look at individual trajectories, you uncover a very different story." — Becca R. Levy, lead author

The strongest predictor: age beliefs

The researchers then asked why some people improved and others didn’t. Positive beliefs about aging — measured near the start of the study — predicted improvement in both cognition and walking speed, and the relationship held even after adjusting for age, sex, education, chronic disease, depression and length of follow-up. This builds on Levy’s earlier "stereotype embodiment theory," which has separately linked negative age beliefs to worse memory, slower walking and biomarkers associated with Alzheimer’s disease.

Why this matters beyond the headline

This is one study, and age beliefs are correlational rather than proven causal levers — the authors themselves frame it as opening the door to intervention research, not closing the case. But the core empirical finding (individual trajectories diverge sharply from population averages, and improvement is common rather than rare) is a useful corrective to the fatalism that often drives people to stop investing in training, nutrition and cognitive engagement as they get older.

Misi’s longevity stack exists for exactly this reason: strength, VO2max, protein and sleep are trainable at any age, and the trend line in your own PhenoAge and fitness-age data over successive quarters is a more honest predictor of your trajectory than an assumption about what "getting older" is supposed to look like.