Researchers have identified in a new study that loneliness during childhood was associated with accelerated cognitive decline and risk of dementia in middle and older ages. The study was published inJAMA Network Openby Jinqi W. and colleagues. This indicates that mitigating loneliness in childhood is a significant strategy to prevent dementia throughout the lifespan. The study was conducted with data from the nationally representative China Health and Retirement Longitudinal Study cohort, which followed participants from June 2011 to December 2018, with a maximum follow-up of 7 years. 13,592 participants were included in the analysis with a mean age of 58.34 years (SD 9.39), and 52.8% were female (n=7175). Childhood loneliness was operationalized as recurrent loneliness and not having close friends by age 17. Adult loneliness was measured with a standardized single item from the Centre for Epidemiological Studies Depression Scale. Cognitive endpoints were episodic memory and executive function, with dementia diagnosed clinically or identified through the presence of cognitive and functional deficits. Statistical methods used linear mixed-effects models for cognitive impairment and Cox proportional hazards regression models for risk of dementia. • Possible childhood loneliness was reported by 6525 (48.0%) of the total participants, and clear childhood loneliness was reported by 565 (4.2%) participants. • Both groups had significant correlations with long-term brain health outcomes. • Childhood loneliness correlated with accelerated cognitive decline, with β coefficients of −0.03 (95% CI, −0.05 to −0.02) SD/year for loneliness and −0.02 (95% CI, −0.02 to −0.01) SD/year for potential loneliness. • Notably, childhood loneliness also predicted a higher risk of dementia (HR 1.41; 95% CI, 1.03–1.93). • These relationships remained after controlling for adult loneliness and even when analysis was limited to participants without adult loneliness. Adult loneliness was a partial mediator but not a modifier. • Adult loneliness mediated 8.5% (95% CI, 2.9%–14.1%) of the association between childhood loneliness and cognitive decline, and 17.2% (95% CI, 4.9%–29.5%) of the association between childhood loneliness and risk for dementia. •Adult loneliness, however, failed to significantly modify the strength of either association, such that the risk associated with early experiences remained independently significant. In this cohort study, childhood loneliness was associated with cognitive decline and dementia risk in middle and later adulthood, even in the absence of adult loneliness. Early interventions aimed at reducing childhood loneliness may help promote lifelong cognitive health and reducing dementia risk. Wang J, Jiao D, Zhao X, et al. Childhood Loneliness and Cognitive Decline and Dementia Risk in Middle-Aged and Older Adults. JAMA Netw Open. 2025;8(9):e2531493. doi:10.1001/jamanetworkopen.2025.31493