title: Intrapair Comparison of Life-Course Appetite and Physical Activity in Elderly Danish Twins: Reliability and Association With Subsequent Survival.
abstract: Avoiding overeating and being physically active is associated with healthy aging, but methodological issues challenge the quantification of the association. Intrapair comparison of twins is a study design that attempts to minimize social norm-driven biased self-reporting of lifestyle factors. We aimed to investigate the association between self-reported lifestyle factors and subsequent survival in 347 Danish twin pairs aged 70 years and older and, additionally, to investigate the reliability of these self-reports. The twins were interviewed in 2003 and followed for mortality until 2015. They were asked to compare their appetite and physical activity to that of their co-twins in different stages of life. On an individual level, we found a positive association between current self-reported physical activity and late-life survival for elderly twins. This was supported by the intrapair analyses, which revealed a positive association between midlife and current physical activity and late-life survival. A positive association between lower appetite and late-life survival was found generally over the life course in the individual level analyses but not in the intrapair analyses. Kappa values for the inter-twin agreement on who ate the most were 0.16 to 0.34 in different life stages, and for physical activity 0.19 to 0.26, corresponding to a slight-to-fair agreement. Approximately, 50% of the twin pairs were not in agreement regarding physical activity, and of these twins 75% (95% CI: 67-82%) considered themselves the most active twin. These findings indicate a still-existing tendency of answering according to social norms, even in a twin study designed to minimize this.
authors.affiliation: Department of Public Health,Unit of Epidemiology, Biostatistics and Biodemography,University of Southern Denmark,Odense,Denmark.
authors.forename: Laura E
authors.initials: LE
authors.lastname: Løkkegaard
authors.affiliation: Department of Public Health,Unit of Epidemiology, Biostatistics and Biodemography,University of Southern Denmark,Odense,Denmark.
authors.forename: Lisbeth A
authors.initials: LA
authors.lastname: Larsen
authors.affiliation: Department of Public Health,Unit of Epidemiology, Biostatistics and Biodemography,University of Southern Denmark,Odense,Denmark.
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001066:Appetite / Q000502:physiology*; D003718:Denmark; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D057566:Self Report; D014427:Twins
keywords: appetite; elderly; physical activity; reliability; self-report; survival; twins