The genetic component of discrete disability traits: an analysis using liability models with age-dependent thresholds

Area of Science:

• Gerontology
• Behavioral Genetics
• Epidemiology

Background:

• Aging populations present challenges in maintaining Activities of Daily Living (ADL).
• Understanding the genetic and familial influences on disability is crucial for targeted interventions.
• Twin studies provide a powerful design to disentangle genetic from environmental factors.

Purpose of the Study:

• To investigate the presence and significance of familial and genetic effects on ADL disability in older Danish twins.
• To analyze these effects across different disability scales and for both males and females.
• To explore age-dependent thresholds in disability models.

Main Methods:

• Utilized multithreshold liability models for discrete disability scores.
• Analyzed data from the 1995 Longitudinal Study of Aging of Danish Twins (LSADT) for individuals over 75.
• Incorporated age-dependent thresholds into the disability models.

Main Results:

• Familial effects were observed in all five disability scales for females and three for males.
• Significant genetic effects were found in the Upper Limb-T scale (females) and PADL-H scale (males).
• Genetic influences were pronounced in Mobility-T (females) and Lower Limb-T (males and females) scales, with sex-specific patterns in tiredness vs. need-for-help scales.

Conclusions:

• Both familial and genetic factors play a significant role in ADL disability among older Danish twins.
• Genetic effects appear more pronounced for tiredness-related disabilities in females and need-for-help in males.
• Increased sample sizes may reveal further genetic influences on ADL disability.