Population-specific predictors of obesity hypoventilation syndrome: A systematic review of South Asian and selected Western cohorts

Background Obesity hypoventilation syndrome (OHS) is underdiagnosed in ethnically diverse populations where Western-derived screening guidelines may not apply. This systematic review synthesizes evidence from South Asian and selected Western cohorts to characterize population-specific OHS predictors. Methods PubMed/MEDLINE, Embase, and Cochrane Library were searched (inception to April 2026) for peer-reviewed studies of adults with BMI ≥30 kg/m² and OHS confirmed by daytime PaCO₂ >45 mmHg. Two reviewers performed data extraction, risk-of-bias assessment (Newcastle–Ottawa Scale), and GRADE evidence grading. Quantitative pooling was not performed due to heterogeneity in study design, sampling frames, and outcome definitions. Results Six studies (1,056 participants; India, US, Spain) were included. South Asian cohorts developed OHS at BMI thresholds 4 to 9 kg/m² below Western benchmarks (cutoff 30.95 kg/m²; AUC 0.742). Female sex was the strongest independent predictor in one South Asian cohort (OR 4.1; 95% CI 1.6–10.4; p=0.003). Minimum nocturnal SpO₂ ≤60% showed strong discrimination (AUC 0.883; sensitivity 90%, specificity 85%). Spirometric restriction was consistent across cohorts (FVC 63–78% predicted). One study found OHS patients produced more CO₂ than eucapnic obese controls (336±79 mL/min) at comparable minute ventilation, a finding requiring confirmation in larger cohorts. Conclusions OHS predictors from Western, male-predominant cohorts may not generalize to South Asian populations (six heterogeneous studies; three countries). Lower BMI thresholds, female sex as a South Asian predictor, and nocturnal SpO₂ desaturation are hypothesis-generating signals requiring prospective validation. Excess CO₂ production (one small cohort) requires replication but, if confirmed, would support weight reduction as a complementary target alongside PAP therapy.