title: Does telomere length predict decline in physical functioning in older twin sisters during an 11-year follow-up?
abstract: Leukocyte telomere length (LTL) is known to be associated with mortality, but its association with age-related decline in physical functioning and the development of disability is less clear. This study examined the associations between LTL and physical functioning, and investigated whether LTL predicts level of physical functioning over an 11-year follow-up. Older mono- (MZ) and dizygotic (DZ) twin sisters (n = 386) participated in the study. Relative LTL was measured by qPCR at baseline. Physical functioning was measured by 6-min walking distance and level of physical activity (PA). Walking distance was measured at baseline and at 3-year follow-up. PA was assessed by questionnaire at baseline and at 3- and 11-year follow-ups. The baseline analysis was performed with path models, adjusted with age and within-pair dependence of twin pairs. The longitudinal analysis was performed with a repeated measures linear model adjusted for age and longitudinal within-pair dependence. A nonrandom missing data analysis was utilized. At baseline, in all individuals, LTL was associated with PA (est. 0.14, SE 0.06, p = 0.011), but not with walking distance. Over the follow-up, a borderline significant association was observed between LTL and walking distance (est. 0.14, SE 0.07, p = 0.060) and a significant association between LTL and PA (est. 0.19, SE 0.06, p = 0.001). The results suggest that LTL is associated with PA and may, therefore, serve as a biomarker predicting the development of disability. Longitudinal associations between LTL and PA were observed only when nonrandom data missingness was taken into account in the analysis.
authors.affiliation: Gerontology Research Center, Department Health Sciences, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland. elina.sillanpaa@jyu.fi.
authors.forename: Elina
authors.initials: E
authors.lastname: Sillanpää
authors.affiliation: Gerontology Research Center, Department Health Sciences, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Törmäkangas
authors.affiliation: Gerontology Research Center, Department Health Sciences, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.
authors.forename: Taina
authors.initials: T
authors.lastname: Rantanen
authors.affiliation: Department of Public Health, University of Helsinki, Helsinki, Finland.|National Institute for Health and Welfare, Helsinki, Finland.|Institute for Molecular Medicine (FIMM), University of Helsinki, Helsinki, Finland.
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.affiliation: Gerontology Research Center, Department Health Sciences, University of Jyväskylä, P.O. Box 35, 40014, Jyväskylä, Finland.
authors.forename: Sarianna
authors.initials: S
authors.lastname: Sipilä
mesh_terms: D000368:Aged; D000375:Aging; D018450:Disease Progression; D004200:Diseases in Twins / Q000378:metabolism / Q000401:mortality* / Q000503:physiopathology; D005260:Female; D005387:Finland / Q000453:epidemiology; D005544:Forecasting; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D008875:Middle Aged; D051346:Mobility Limitation; D009043:Motor Activity; D015996:Survival Rate / Q000639:trends; D016615:Telomere / Q000502:physiology*; D014427:Twins
keywords: Biological aging; Missing data not at random; Physical activity; Physical functioning; Six-minute walking test; Telomere; Twin study