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Key findings

  • Social isolation trended with lower serum BDNF, and having emotional support available was significantly associated with higher BDNF
  • Having someone available to listen or provide emotional support was associated with significantly reduced dementia risk
  • Stroke-free participants who had someone available to listen were at significantly lower risk of subsequent stroke

Lower levels of brain-derived neurotrophic factor (BDNF), a molecule critical for synaptic plasticity and neuronal repair, are known to be associated with increased risk of stroke and neuropathology that accompanies dementia. Likewise, having a small social network has been linked with increased risk of stroke and cognitive dysfunction.

Joel Salinas, MD, MBA, MSc, chief of the McCance Brain Health Unit, and Jonathan Rosand, MD, chief of Neurocritical Care and Emergency Neurology, and colleagues were the first group to investigate whether BDNF might be a biological link between social relationships and the likelihood of stroke or dementia. In Alzheimer’s & Dementia: Translational Research & Clinical Interventions, they conclude that social support was indeed associated with BDNF levels, and therefore BDNF may be a key mechanism underlying social determinants of stroke and dementia.

The research team analyzed 3,294 participants from the original Framingham Heart Study, which was started in 1948, and the Framingham Offspring Study, which was started in 1978. In these studies, BDNF was measured and social relationships were quantified with the Berkman–Syme Social Network Index, which is a self-reported questionnaire that measures the extent of social isolation or social connectedness regarding 4 types of contacts: marriage, sociability with close friends and relatives, participation in religious meetings or services and participation in other community organizations. The index also measures how often support is available in terms of listening, advice-giving, affection and emotional support.

The participants were available for cross-sectional analysis of associations between social relationships and BDNF. The average age was 65 years, 56% were women and four percent reported social isolation. There was a trend for social isolation to be associated with lower serum BDNF (P = .052), although social connectedness was not. Having someone available to provide emotional support most (or all of) the time was significantly associated with higher BDNF.

The researchers retrospectively analyzed the associations between social relationships and dementia (n=1,834) and stroke (n=3,210). Over a median follow-up period of 11 years, 13% of participants developed dementia and six percent had new-onset stroke. Neither social isolation nor social connectedness was associated with dementia or stroke.

However, participants who had someone available to listen to them most (or all of) the time had a 41% reduced risk for stroke (hazard ratio [HR], 0.59; 95% confidence interval [CI], 0.41–0.83; = .003) and a 33% reduced risk of dementia (HR, 0.67; 95% CI, 0.49–0.92; = .01). Having someone provide emotional support most (or all of) the time was associated with a 31% reduced risk of dementia (HR, 0.69; 95% CI, 0.51–0.94; P = .02).

The authors emphasize that an observational study cannot establish causal relationships between social isolation and neurologic disease, and they call for other types of research. For now, they conclude that simply helping older adults gain companionship and emotional support may reduce their risks of stroke and dementia.

41%
Reduced risk of stroke among people who often had someone available to listen

33%
Reduced risk of dementia among people who often had someone available to listen

31%
Reduced risk of dementia among people who often had someone providing emotional support

Learn more about the McCance Brain Health Unit

Learn more about neurocritical care at Mass General

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