Sex-specific associations of social isolation and loneliness with residual life expectancy at age 45 years among middle-aged and older adults in China.

Background: Globally, one-third of older adults experience social isolation or loneliness, making them critical public health priorities. However, the impact of social isolation and loneliness on life expectancy remains underexplored. This study investigated the separate and joint associations of social isolation and loneliness with residual life expectancy at age 45 years, alongside the sex-specific variations in these associations with the aim of informing targeted strategies for mitigating social health disparities in rapidly ageing populations.

Methods: This prospective cohort study was conducted using data from the China Health and Retirement Longitudinal Study. A total of 11,315 community dwellers (5,274 men; 6,041 women) aged 45 years and above included. After the baseline 2011 assessment year, participants from the 2013, 2015, 2018, and 2020 waves were followed up. The measurements included the following: social isolation, assessed on the basis of social network usage, activities, and engagements; loneliness, evaluated on the basis of the subjective feeling of loneliness; and a flexible parametric Royston-Parmar model to estimate hazard ratios (HR) for all-cause mortality and to predict residual life expectancy differences.

Results: In men, socially isolated and lonely individuals had the greatest reduction in residual life expectancy at age 45 years, losing 4.61 years (95% CI: 1.49-7.74) compared to those with neither experience. Social isolation alone (3.82 years lost) and loneliness alone (2.83 years lost) resulted in significant reductions. In women, social isolation alone was significantly associated with reduced residual life expectancy (3.11 years lost, 95% CI: 0.68-5.55), whereas loneliness alone and combined exposure did not show statistically significant effects.

Conclusions: Significant sex-specific differences were identified in the impact of social isolation and loneliness on residual life expectancy. Thus, implementing sex-specific public health strategies that focus on dual psychosocial intervention for men and social integration for women is crucial to mitigate premature deaths in ageing populations.