Reader Response: Associations of Social Isolation and Loneliness With Later Dementia
TomoyukiKawada, Professor, Nippon Medical School
Submitted June 09, 2022
Shen et al. investigated the association of social isolation and loneliness with dementia.1 They also measured gray matter volumes (GMVs). The adjusted hazard ratios (95% CIs) of social isolation and loneliness for dementia were 1.26 (1.15-1.37) and 1.04 (0.94-1.16), respectively. In addition, socially isolated individuals had lower GMVs in the temporal, frontal, and other brain regions; the authors speculated that GMVs partly mediated the association between social isolation at baseline and subsequent cognitive function.
Regarding the mechanism of the association, I cannot accept the concept of social isolation-related lower GMVs. Genetic and molecular basis of mitochondrial dysfunction and oxidative phosphorylation may be partly and indirectly related to social isolation, and causal direction should be specified by further studies.2
Functional decline may be closely related to cognitive decline and dementia.3 Fujiwara et al. conducted a 4-year prospective study in which the significant association between social isolation and functional decline was observed only in men.4 This means that sex may have a possibility of interaction with social isolation and/or dementia. When conducting a long-term follow-up study, physio-psychosocial functions should be included for the risk assessment of dementia, stratified by sex.
Disclosure
The author reports no relevant disclosures. Contact journal@neurology.org for full disclosures.
References
Shen C, Rolls E, Cheng W, et al. Associations of Social Isolation and Loneliness With Later Dementia [published online ahead of print, 2022 Jun 8]. Neurology. 2022;10.1212/WNL.0000000000200583.
Drinkwater E, Davies C, Spires-Jones TL. Potential neurobiological links between social isolation and Alzheimer's disease risk [published online ahead of print, 2021 Jun 28]. Eur J Neurosci. 2021;10.1111/ejn.15373. doi:10.1111/ejn.15373
De Looze C, Williamson W, Demnitz N, O'Connor D, Hernández B, Kenny RA. Physical function, an adjunct to brain health score for phenotyping cognitive function trajectories in older age: Findings from the Irish Longitudinal Study on Ageing (TILDA) [published online ahead of print, 2022 Jan 29]. J Gerontol A Biol Sci Med Sci. 2022;glac024. doi:10.1093/gerona/glac024
Fujiwara Y, Nishi M, Fukaya T, et al. Synergistic or independent impacts of low frequency of going outside the home and social isolation on functional decline: A 4-year prospective study of urban Japanese older adults. Geriatr Gerontol Int. 2017;17(3):500-508. doi:10.1111/ggi.12731
Shen et al. investigated the association of social isolation and loneliness with dementia.1 They also measured gray matter volumes (GMVs). The adjusted hazard ratios (95% CIs) of social isolation and loneliness for dementia were 1.26 (1.15-1.37) and 1.04 (0.94-1.16), respectively. In addition, socially isolated individuals had lower GMVs in the temporal, frontal, and other brain regions; the authors speculated that GMVs partly mediated the association between social isolation at baseline and subsequent cognitive function.
Regarding the mechanism of the association, I cannot accept the concept of social isolation-related lower GMVs. Genetic and molecular basis of mitochondrial dysfunction and oxidative phosphorylation may be partly and indirectly related to social isolation, and causal direction should be specified by further studies.2
Functional decline may be closely related to cognitive decline and dementia.3 Fujiwara et al. conducted a 4-year prospective study in which the significant association between social isolation and functional decline was observed only in men.4 This means that sex may have a possibility of interaction with social isolation and/or dementia. When conducting a long-term follow-up study, physio-psychosocial functions should be included for the risk assessment of dementia, stratified by sex.
Disclosure
The author reports no relevant disclosures. Contact journal@neurology.org for full disclosures.
References