Impact of loneliness on cancer mortality: a systematic review and meta-analysis.

Objective: Loneliness and social isolation can have profound emotional and psychological impact on patients with cancer. Previous studies suggest loneliness may adversely impact cancer prognosis and survival. Potential mechanisms include a variety of biological, psychological and social factors, from impaired ability to access treatment to immune dysregulation. However, its impact is not clearly defined. We conducted the first systematic review and meta-analysis to investigate mortality in relation to loneliness and social isolation among cancer populations. Methods and analysis: We systematically searched MEDLINE, Embase and PsycINFO until 13 September 2024, for studies reporting on the impact of loneliness or social isolation on all-cause and cancer mortality in patients with cancer. Three reviewers independently screened studies, extracted data and assessed bias. A random-effects meta-analysis was used to examine associations between loneliness/social isolation and all-cause and cancer mortality. Results: Of 12 602 citations, 16 studies met eligibility criteria and 13 were included in the meta-analysis. Social isolation and loneliness were most frequently measured using the Social Network Index and UCLA Loneliness Scale, respectively. The median sample size was 6248, with a mean participant age of 63 years. Meta-analysis demonstrated loneliness/social isolation was associated with increased all-cause mortality (HR (95% CI)=1.34 (1.26 to 1.42), p<0.001) and cancer-specific mortality (HR (95% CI)=1.11 (1.02 to 1.21), p=0.014). Conclusion: Loneliness and social isolation may be associated with increased all-cause and cancer-specific mortality in patients with cancer. If these findings are confirmed by future, more definitive studies, together they support the need to incorporate psychosocial assessments and targeted interventions into cancer care to improve patient outcomes. PROSPERO registration number: CRD42024590482.