Genetic and environmental influences on longitudinal frailty trajectories from adulthood into old age

Jonathan K L Mak, Ralf Kuja-Halkola, Ge Bai, Linda B Hassing, Nancy L Pedersen, Sara Hägg, Juulia Jylhävä, Chandra A Reynolds

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Abstract

BACKGROUND: Frailty is a complex, dynamic geriatric condition, but limited evidence has shown how genes and environment may contribute to its longitudinal changes. We sought to investigate sources of individual differences in the longitudinal trajectories of frailty, considering potential selection bias when including a sample of oldest-old twins.

METHODS: Data were from two Swedish twin cohort studies: a younger cohort comprising 1,842 adults aged 29-96 years followed up to 15 waves, and an older cohort comprising 654 adults aged ≥79 years followed up to five waves. Frailty was measured using the frailty index (FI). Age-based latent growth curve models were used to examine longitudinal trajectories, and extended to a biometric analysis to decompose variability into genetic and environmental etiologies.

RESULTS: A bilinear model with an inflection point at age 75 best described the data, indicating a four- to five-fold faster FI increase after 75 years. Twins from the older cohort had significantly higher mean FI at baseline but slower rate of increase afterwards. FI level at age 75 was moderately heritable in both men (42%) and women (55%). Genetic influences were relatively stable across age for men and increasing for women, although the most salient amplification in FI variability after age 75 was due to individual-specific environmental influences for both men and women; conclusions were largely consistent when excluding the older cohort.

CONCLUSION: Increased heterogeneity of frailty in late life is mainly attributable to environmental influences, highlighting the importance of targeting environmental risk factors to mitigate frailty in older adults.

Original languageEnglish
Pages (from-to)333–341
Number of pages9
JournalThe journals of gerontology. Series A, Biological sciences and medical sciences
Volume78
Issue number2
Early online date17 Sept 2022
DOIs
Publication statusPublished - 2023
Publication typeA1 Journal article-refereed

Publication forum classification

  • Publication forum level 3

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