title: Common genetic factors influence hand strength, processing speed, and working memory.
abstract: BACKGROUND
  It is important to detect cognitive decline at an early stage, especially before onset of mild cognitive impairment and dementia. Processing speed and working memory are aspects of cognitive function that are associated with cognitive decline. Hand strength is an inexpensive, easily measurable indicator of cognitive decline. However, associations between hand strength, processing speed, and working memory have not been studied. In addition, the genetic and environmental structure of the association between hand strength and cognitive decline is unclear. We investigated phenotypic associations between hand strength, processing speed, and working memory and examined the genetic and environmental structure of the associations between phenotypes.
  
  
  METHODS
  Hand strength, processing speed (digit symbol performance), and working memory (digit span performance) were examined in monozygotic and dizygotic twin pairs. Generalized estimating equations were used to identify phenotypic associations, and structural equation modeling was used to investigate the genetic and environmental structure of the association.
  
  
  RESULTS
  Generalized estimating equations showed that hand strength was phenotypically associated with digit symbol performance but not with digit span performance. Structural equation modeling showed that common genetic factors influenced hand strength and digit symbol and digit span performance.
  
  
  CONCLUSIONS
  There was a phenotypic association between hand strength and processing speed. In addition, some genetic factors were common to hand strength, processing speed, and working memory.
authors.affiliation: Department of Health Promotion Science, Osaka University Graduate School of Medicine.
authors.forename: Soshiro
authors.initials: S
authors.lastname: Ogata
authors.forename: Kenji
authors.initials: K
authors.lastname: Kato
authors.forename: Chika
authors.initials: C
authors.lastname: Honda
authors.forename: Kazuo
authors.initials: K
authors.lastname: Hayakawa
mesh_terms: D000328:Adult; D000368:Aged; D003072:Cognition Disorders / Q000235:genetics / Q000503:physiopathology; D005260:Female; D059647:Gene-Environment Interaction; D018737:Hand Strength / Q000502:physiology*; D006801:Humans; D007564:Japan; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D008606:Mental Processes / Q000502:physiology*; D008875:Middle Aged; D010641:Phenotype; D012042:Registries; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic