Loneliness, social isolation, their synergistic interaction, and mortality.

A small number of studies point to cumulative effects of loneliness and isolation in mid-life and older adulthood on health, disability and quality of life, and synergistic effects on mortality risk.

“While a small number of studies point to cumulative effects of loneliness and isolation in mid-life and older adulthood on health, disability and quality of life (Barnes et al., 2021;Shimada et al., 2025), as well as synergistic effects on mortality risk (Beller & Wagner, 2018;Foster et al., 2023;Ward et al., 2021), these studies have largely relied on cross-sectional data and focused on physical”

Social isolation and loneliness are distinct concepts and are only weakly correlated with each other.

“That the two concept are distinct is supported by several studies that show that they are only weakly correlated with each other [18–21].”

Beller and Wagner showed a significant interaction between social isolation and loneliness on mortality, with the effect of social isolation becoming stronger at higher levels of loneliness.

“Beller and Wagner [18] showed a significant interaction, with the effect of social isolation becoming stronger at higher levels of loneliness, suggesting that being both socially isolated and lonely confers a much higher mortality risk than being only socially isolated or only lonely.”

The socially isolated and lonely group was the most at-risk group.

“The socially isolated and lonely group was clearly the most at risk group, as expected, consistent with previous research [18,45].”