We often hear that 60 is the new 50 and 70 the new 60. It is a bromide borne out by old photos. Just check out images of your grandparents or great-grandparents (depending on your age) and notice their stooped and soft bodies, their lined faces and how they seem anchored in their chairs when they were barely pushing 60. What a contrast with vigorous, gym-going sexagenarians of today!

Recent studies comparing populations born in different decades have looked beyond these surface impressions to nail down actual physical and mental differences in the ways we are aging. This research has identified particular areas of improvement. But these gains are not across the board, and they appear to depend on social, behavioral and economic factors.

A pair of new studies from Finland—one looking at physical aging and one looking at cognitive aging—strikingly demonstrates some of the details of generational change. The research, overseen by gerontologist Taina Rantanen of the University of Jyväskylä, compares adults born in 1910 and 1914 with those born roughly 30 years later. The two age groups were assessed in 1989 and 1990 and in 2017 and 2018, respectively. The beauty of this work is that both birth cohorts were examined in person at age 75 and again at 80 with the same substantial battery of six physical tests and five measures of cognition. Most cohort studies look at a narrower range of measures, and many of them rely on self-assessments.

The later-born group could walk faster, had a stronger hand grip and could exert more force with their lower leg. Such metrics are reliable predictors of disability and mortality. On cognitive tests, the later cohort had better verbal fluency (naming more words beginning with a K in three minutes), clocked faster reaction time on a complex finger-movement task, and scored higher on a test matching numbers to symbols.

But not everything changed across the generations: measures of lung function were surprisingly static, and there was no improvement in the short-term-memory task of recalling a string of digits—possibly because rote memorization has been de-emphasized in school and in daily life in recent decades, the researchers suspect.

Many of these findings fit with other cohort studies. For example, a Dutch study of cognitive aging published in 2018 showed that elderly adults born between 1931 and 1941 outshone same-age adults born in the 1920s on a range of cognitive measures—though again not on short-term memory. And a 2013 Danish study revealed that birth-year-related differences can persist into very old age: 95-year-olds born in 1915 outperformed 93-year-olds born in 1905 on a cognitive exam. The later-born Danish cohort did no better on measures of gait speed and grip strength, but its members were more adept at activities of daily living—such as bathing and dressing—perhaps because of their improved cognitive status.

There are many reasons that people are aging better, including improved medical care and a drop in smoking, but the factors that loomed largest in the Finnish study of physical function, lead author Kaisa Koivunen says, were that the later-born adults were more physically active and had bigger bodies, which suggests better nutrition. (In 1943 Finland became the world's first country to require universal free lunch at school.) For brain function, the key seems to be more years of education. In both the Finnish and the Dutch studies, cognitive differences between the cohorts largely disappeared when researchers controlled for this factor.

Education is a powerful influence on aging and health, says Luigi Ferrucci, scientific director of the U.S. National Institute on Aging: “With more education, you are probably going to have a larger income, which means you are more likely to go to the doctor, have good nutrition and have a job that is not eviscerating your body.” In prosperous countries, these advantages have not only lengthened life but most likely ensured that more years are spent in good health.

In the U.S., Ferrucci says, the benefits of prosperity are less equally distributed than in Finland or Denmark. He points out that the average life span is seven years shorter in a poor state such as Mississippi than in a wealthier one such as California. “Here we still have lots of people who cannot take the drugs they need because they cannot pay for them,” he says, and they may lack access to healthy foods and opportunities for exercise and learning that extend our vital years. In short, 70 may be the new 60 for many of us but not for all.