title: Social relationships and risk of dementia: a population-based study.
abstract: BACKGROUND
  The objective was to examine whether aspects of social relationships in old age are associated with all-cause dementia and Alzheimer's disease (AD).
  
  
  METHODS
  We studied 1,715 older adults (≥ 65 years) who were dementia-free at baseline over a period of up to 16 years. Data on living status, contact/visit frequency, satisfaction with contact frequency, and having/not having a close friend were analyzed using Cox proportional hazards regressions with all-cause dementia or AD as the dependent variable. To control for reverse causality and to identify potential long-term effects, we additionally performed analyses with delayed entry.
  
  
  RESULTS
  We identified 373 incident cases of dementia (207 with AD) during follow-up. The variable visiting/visits from friends was associated with reduced risk of all-cause dementia. Further, a higher value on the relationships index (sum of all variables) was associated with reduced risk of all-cause dementia and AD. However, in analyses with delayed entry, restricted to participants with a survival time of three years or more, none of the social relationship variables was associated with all-cause dementia or AD.
  
  
  CONCLUSIONS
  The results indicate that certain aspects of social relationships are associated with incident dementia or AD, but also that these associations may reflect reverse causality. Future studies aimed at identifying other factors of a person's social life that may have the potential to postpone dementia should consider the effects of reverse causality.
authors.affiliation: Department of Psychology,Umeå University,S-901 87 Umeå,Sweden.
authors.forename: Daniel Eriksson
authors.initials: DE
authors.lastname: Sörman
authors.affiliation: Department of Psychology,Umeå University,S-901 87 Umeå,Sweden.
authors.forename: Michael
authors.initials: M
authors.lastname: Rönnlund
authors.affiliation: Department of Psychology,Umeå University,S-901 87 Umeå,Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Sundström
authors.affiliation: Department of Clinical Sciences,Division of Psychiatry,Umeå University,S-901 85 Umeå,Sweden.
authors.forename: Rolf
authors.initials: R
authors.lastname: Adolfsson
authors.affiliation: Aging Research Center (ARC),Karolinska Institutet,S-113 30 Stockholm,Sweden.
authors.forename: Lars-Göran
authors.initials: LG
authors.lastname: Nilsson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000209:etiology / Q000523:psychology; D015984:Causality; D003704:Dementia / Q000209:etiology* / Q000523:psychology; D005260:Female; D006801:Humans; D007398:Interpersonal Relations; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors
keywords: Alzheimer’s disease; dementia; longitudinal; social network; social relationships