Living in a smaller household raises your risk for dementia, according to a study published Tuesday in Scientific Reports. But living with four or more people doesn’t necessarily give you additional protection, the authors noted.
The team used data from the UK Biobank on people aged 50 and up who didn’t have a history of dementia. There were 275,629 participants with an average age of 60 at the start of the study. Over an average follow-up span of 9.5 years, 6,031 people developed all-cause dementia. During the course of the study, researchers documented structural differences from brain scans.
Researchers classified participants with one person in the household as living alone, and those with more than one person as living with someone.
“We found that small household size was associated with a 1.05-fold increased risk of developing dementia,” the authors wrote.
The results showed strong associations between household size and vascular dementia as well as non-Alzheimer’s non-vascular dementia. The risk reduction associated with larger household size was more pronounced for non-Alzheimer’s non-vascular dementia than for vascular dementia.
As the number of household members decreased, the risk of dementia went up, the authors noted. But beyond about four people, the increases in household size didn’t provide additional protection against developing dementia. The team didn’t note an association between household size and Alzheimer’s disease, which is a type of dementia.
“This nuanced relationship highlights the complex interplay between social networks, socioeconomic status, household size and cognitive health,” the authors wrote.
“Consistent with previous population-based studies, our study reaffirms that living alone is a risk factor for dementia,” the authors added.
That’s likely because being with others provides brain stimulation and helps people avoid social isolation that can lead to added stress, the authors explained. Cognitive reserve theory suggests that missing day-to-day companionship and social isolation may lower mental stimulation and weaken neural connectivity, which could lead to cognitive decline. Social isolation may lead to stress responses that include inflammation, which is associated with a higher dementia risk.
Household size may be a potential modifiable risk factor for dementia, the team added.
