Loneliness trajectories and dementia risk: Insights from the HUNT cohort study

Loneliness is postulated to be a risk factor for dementia. However, the findings are inconsistent, and long-term studies on this association remain scarce.

In all, 9389 participants self-reported loneliness in the Trøndelag Health Study (HUNT) in HUNT1 (1984-1986), HUNT2 (1995-1997), and/or HUNT3 (2006-2008) and underwent cognitive assessment in HUNT4 (2017-2019) at age 70 years or older. Logistic regression was employed to analyze the association between the course of loneliness and dementia, with those never lonely as a reference.

In the fully adjusted model, the odds ratio (OR) for persistent loneliness was 1.47 (95% confidence interval [CI] 1.10, 1.95). This attenuated when adjusting for depression (OR 1.28, 95% CI 0.95, 1.72).

Persistent loneliness from midlife into older age, as well as becoming lonely, were associated with increased odds of dementia, whereas transient loneliness in midlife was not. These findings underscore the importance of reducing loneliness.

The study was registered with ClinicalTrials.gov (NCT04786561) and is available online .

Persistent and incident loneliness was associated with a higher risk of dementia.Transient loneliness was not associated with a higher risk of dementia.Loneliness 11 years before to the cognitive assessment was associated with dementia.Reducing the sense of loneliness might reduce or delay the onset of dementia.