Background Low muscle strength predisposes older people to health decline in terms of walking limitations and increased mortality rates. Some studies have reported greater functional reserve capacity in more recently born cohorts, but it is unclear what impact these birth cohort differences have on the associations of muscle strength with walking ability and mortality. We compared the associations of muscle strength with walking speed and mortality risk between two birth cohorts born 28 years apart.

Methods Both cohorts were recruited from the Finnish population register and were examined with identical protocols at ages 75 and 80 years. Participants in the first cohort were born in 1910 and 1914 and were assessed in 1989–1990 (n=500). Participants in the second cohort were born in 1938–1939 and 1942–1943 and were assessed in 2017–2018 (n=726). Maximal walking speed, and maximal isometric grip and knee extension strength were measured at the research center. Mortality was ascertained from registers over five years of follow-up. Linear and Cox regression models were used to estimate the associations between strength, walking speed and mortality and interactions by birth cohort.

Results The later born men and women had 13% and 20% faster walking speed, respectively, compared to the earlier born cohort (p<.001). Knee extension strength was 18% higher in the later born men and 26% higher in the later born women (p<.001). Grip strength was 8% higher in later born men and 10% higher in later born women (p<.001). Mortality rates were lower in the later born birth cohort (in men, 2.63 deaths per 100 person-years vs. 4.21 and in women, 1.22 vs. 3.71). Better grip and knee extension strength were associated with faster walking speed and lower mortality hazards in both sexes and birth cohorts when adjusted for age and education. Most associations were similar between the cohorts. Only in men, the association between knee extension strength and walking speed was weaker in the more recent born cohort compared to the earlier born cohort (B -.243, SE .073, 95% CI -.387; -.100).

Conclusion Older Finnish adults born in the 1930s and 1940s have better muscle strength and walking speed and lower mortality compared with a cohort born three decades earlier. Muscle strength remains a significant predictor of walking speed and mortality despite these birth cohort differences. However, the higher muscle strength reserve of more recently born cohorts may help them to maintain walking ability and health for longer.