Higher age, low education, genetic vulnerability, earlier head injury, mild cognitive impairment, stroke, hypertension, dyslipidaemia, hyperinsulinaemia, type 2 diabetes, obesity, subclinical atherosclerosis and cardiac arrhythmias are the known risk factors for dementia.Depression social isolation are also associated with increased risk .Having an extensive social network and social resources is associated with less cognitive decline in old age.
What about loneliness? It is unclear to what extent social isolation and feelings of loneliness specifically contribute to the onset of dementia, especially when other known risk factors are adjusted for.
Amsterdam Study of the Elderly (AMSTEL) is a prospective community-based cohort study.Tjalling Jan Holwerda et al examined the association between social isolation, feelings of loneliness and dementia at 3-year follow-up as part of this larger study.
A total of 5666 older persons were randomly selected from the population and at the 3-year follow-up,16% had died, 7.0% were too ill or cognitively impaired to participate, 16% refused to participate, and 5% were no longer available for other reasons.participants with dementia at baseline (3%) were excluded, leaving 2173 participants for this analysis.
At baseline, 46 % participants were living alone, 51 % were not or no longer married, and 73 % were not receiving social support. A total of 20% older persons reported feelings of loneliness.
Of the participants living alone at baseline, 9.3% had developed dementia at 3 years follow-up compared with 5.6% of participants living with others. Of participants not or no longer married, 9.2% had developed dementia compared with 5.3% of those who were married.Of participants with feelings of loneliness at baseline, 13.4% met criteria for dementia at 3 years compared with 5.7% of participants without such feelings.
The association between feelings of loneliness and incident dementia was examined with stepwise adjustment for potential confounding and explanatory variables. The adjusted OR in the final model was 1.64 (95% CI 1.05 to 2.56) for feelings of loneliness, signifying an increased risk of incident dementia. The objective aspects of social isolation (living situation and marital status) did not show such an association after adjustment.
Feelings of loneliness independently contribute to the risk of dementia in later life. Authors argue that the observation that ‘feeling lonely’ rather than ‘being alone’ was associated with dementia onset suggests that it is not the objective situation, but rather the perceived absence of social attachments that increases the risk of cognitive decline.
There are three potential explanations for this association. 1. Loneliness may affect cognitive and memory systems by reducing cognitive activity and decreasing neural reserve i.e. contribute to dementia 2. Loneliness may be a consequence of preclinical dementia ( behavioural reaction to impaired cognition or as a consequence of undetected pathology contributing to dementia). 3. Feelings of loneliness could be an indicator of unfavourable premorbid personality traits and behaviour which are risk factors for dementia , for example distress proneness has been shown to be a risk factor for the development of Alzheimer’s disease.
Limitations: Severity and extent of loneliness was not assessed using more comprehensive tools. Structural aspects of social relationships (number of contacts and network size) were not studied. Information whether feelings of loneliness had developed recently or whether they were part of an enduring condition or personality trait was not collected.
Feelings of loneliness were associated with development of dementia . Social isolation or depression could not account for this association. Whether cognitive deterioration and dementia are a consequence of feelings of loneliness or whether feelings of loneliness are a behavioural reaction to diminished cognition is unknown.
Summary of the article:
Feelings of loneliness, but not social isolation, predict dementia onset: results from the Amsterdam Study of the Elderly (AMSTEL).Holwerda TJ, Deeg DJ, Beekman AT, van Tilburg TG, Stek ML, Jonker C, Schoevers RA. J Neurol Neurosurg Psychiatry. 2014 Feb;85(2):135-42.