A Comparative Evaluation of Three Large Language Models for Parent-Centered Questions About Anorexia Nervosa.

The aging process is characterized by an involuntary reduction in muscle mass and strength, resulting from a combination of genetic, environmental, and lifestyle factors, along with their intricate interplay (). Muscle strength begins to gradually decline from around the age of 30, but significant changes in the aging process occur after the age of 50, with an annual diminishing of muscle strength by 1%–2% (). Low muscle strength is associated with an increased risk of chronic diseases, disability, and mortality (,). Among modifiable factors, physical activity (PA) plays a key role in preserving muscle strength and mitigating age-related decline. Regular PA can counteract losses in muscle mass and function, supporting mobility and reducing the risk of disability (). At the same time, reduced muscle strength may lead to lower PA engagement, creating a feedback loop that accelerates physical decline (). Conversely, greater muscle strength can enhance one’s ability and motivation to remain active, reinforcing long-term physical function and well-being (). Handgrip strength (HGS) is a widely used, reliable marker of overall muscle strength and an important indicator of functional status and health in aging populations (). HGS, even when measured in midlife, predicts future adverse outcomes, including disability and mortality (–). HGS can, therefore, be considered to signal the individual’s intrinsic physiological capacity to resist functional decline into critical disease and disability levels (). HGS is a complex, multifactorial trait affected also by internal factors such as age and sex. Males typically exhibit higher HGS throughout the lifespan, and subtle sex differences have been observed in the rate of age-related decline (,). Classical twin designs among monozygotic (MZ) and dizygotic (DZ) twins, who share 100% and ~50% of their segregating genes, respectively, have shown that HGS is moderately to highly heritable, with genetic factors accounting for 30%–65% of its variance (). This heritability appears relatively stable with age (,,), though some findings suggest environmental influences may increase over time (,). Evidence regarding sex differences in the genetic architecture of HGS is mixed. While one study reports comparable genetic and environmental contributions across sexes (), others have found higher heritability in males (,) and greater shared environmental influence in females (). Additionally, the types of environmental factors that contribute to HGS also appear to differ between sexes across adulthood (). From a genetic perspective, HGS is a polygenic trait, that is, it is influenced by many genes across different loci, each with a low effect (,). A polygenic score (PGS) is a genetic tool used to estimate an individual’s predisposition to a trait or condition, based on the aggregated effect sizes of multiple genetic variants, typically single-nucleotide polymorphisms (SNPs), across the genome (). However, as with many complex traits, PGSs capture only a fraction of the heritability estimated from family-based designs, leaving a substantial proportion of so-called “missing heritability” that may reflect unmeasured genetic effects, gene–environment interplay, or methodological differences between approaches (,). In addition, while the observed sex differences in the genetic architecture of human traits are generally considered to have limited consequences (,), studies have shown that the effects of many disease-specific PGS can vary by age and sex ().