Association between digital biomarkers, loneliness and social isolation: a systematic review and meta-analysis

QuestionWhat is the current evidence base for the association between digital biomarkers from wrist-worn wearables, loneliness and social isolation in adults? Study selection and analysisWe systematically searched six databases from inception to 24th September, 2024. We narratively synthesised findings and pooled effect sizes using random-effects meta-analyses where possible. FindingsWe included 14 studies from 12 articles (12 assessing loneliness, two assessing social isolation). Eight studies used sleep metrics, four used physical activity metrics, and two studies used machine learning approaches. Three meta-analyses were conducted: worse sleep efficiency (SE), but not total sleep time or sleep onset latency, was associated with higher loneliness (Fishers z = -0.20, 95% CI -0.34 to -0.06, p = 0.006). Two studies examined wake after sleep onset (WASO), and found longer periods of WASO were associated with higher loneliness. These findings on loneliness were echoed in the study examining social isolation. One study found that lower total physical activity was associated with higher levels of loneliness and social isolation, while other activity intensities showed mixed evidence. Machine learning studies demonstrated high accuracy in predicting loneliness, though models using digital biomarkers from smartphones provided better accuracy. ConclusionsWorse SE, more WASO, and lower total physical activity were associated with loneliness and social isolation, particularly in middle- and older-age. Digital biomarker-based machine learning studies are sparse but show potential in predicting loneliness. Leveraging digital biomarkers as proxy markers of loneliness and social isolation could facilitate early detection of these conditions. Key messages of the articlesO_ST_ABSWhat is already known on this topicC_ST_ABSLoneliness and social isolation are linked to negative health outcomes, including increased dementia risk. Digital biomarkers have shown potential in detecting mental health conditions and symptoms, but no systematic review has explored their association with loneliness and social isolation. What this study addsThis review identified 14 studies examining the association between digital biomarkers and loneliness or social isolation. Worse sleep efficiency, more wake after sleep onset, and lower physical activity were associated with higher levels of loneliness and social isolation. How this study might affect research, practice or policyDigital biomarkers could support the early detection of loneliness and social isolation, enabling timely intervention.