Healthy ageing from birth to age 84 years in the Helsinki Birth Cohort Study, Finland: a longitudinal study

Background The true prevalence of healthy ageing on a population level is unknown. In this study we aimed to examine the upper limit for the prevalence of healthy ageing, by quantifying the probability of surviving and remaining free of chronic diseases that could impact functioning (ie, healthy survival) across adulthood. We also estimated the prevalence of clinically assessed healthy ageing, and the determinants of healthy survival and healthy ageing.Methods In this longitudinal study, we assessed men and women born in 1934-44 from the Helsinki Birth Cohort Study (Helsinki, Finland; n=13 140). We obtained information on chronic diseases, deaths, and early-to-midlife variables from national registers, databases, and health records for the period Jan 1, 1971, to Dec 31, 2017 (follow-up 951 088 person-years). We also collated data from clinical visits conducted in 2001-04 and 2017-18. Healthy ageing was defined on the basis of clinical data according to six criteria covering chronic diseases, cognitive function, physical performance, depressive symptoms, pain interference, and social functioning. We analysed the probability of healthy survival across adulthood using the Kaplan-Meier method, and the determinants of healthy survival using Cox regression models. We assessed the association of healthy ageing status in 2017-18 (n=813 with available data) with late-midlife factors collected in 2001-04 using age-adjusted logistic regression.Findings The probability of healthy survival was 42 & BULL;8% (95% CI 41 & BULL;6-44 & BULL;0) in men and 40 & BULL;1% (38 & BULL;9-41 & BULL;4) in women at age 65 years, and 22 & BULL;5% (21 & BULL;5-23 & BULL;6%) in men and 24 & BULL;4% (23 & BULL;3-25 & BULL;6) in women at age 75 years. Healthy survival was associated with socioeconomic position in childhood (adjusted hazard ratio [aHR], upper-middle class vs manual worker, men: 1 & BULL;21 [1 & BULL;11-1 & BULL;31]; women: 1 & BULL;15 [95% CI 1 & BULL;05-1 & BULL;26]) and years of education (aHR per 1 SD increase, men: 1 & BULL;12 [1 & BULL;08-1 & BULL;16]; women: 1 & BULL;03 [1 & BULL;00-1 & BULL;07]). In men, healthy survival was also associated with lower maternal BMI in late pregnancy (aHR per 1 SD increase 0 & BULL;93 [0 & BULL;90-0 & BULL;96]), and in women, with shorter height at age 7 years (aHR per 1 SD increase 0 & BULL;95 [0 & BULL;91-0 & BULL;99]). Among the 813 individuals with relevant clinical assessment data, 159 (19 & BULL;6%) met all six criteria for healthy ageing at mean age 76 years (SD 3). In addition to age, we found that nutrition (Alternative Healthy Eating Index, age-adjusted odds ratio [aOR] per 1 point increase 1 & BULL;03 [1 & BULL;01-1 & BULL;05]), former smoker status (vs non-smoker status, aOR 0 & BULL;68 [0 & BULL;47-0 & BULL;98], and use of lipid-lowering medication (vs not used, aOR 0 & BULL;60 [0 & BULL;42-0 & BULL;87]) in late midlife (mean age 61 years [SD 3]) were associated with healthy ageing.Interpretation The probability of healthy survival, as the upper limit for healthy ageing, was less than 50% from age 65 years. The probability of healthy survival and healthy ageing was influenced by several factors across the life course. Promotion of healthy ageing needs to take a life course approach.