CARDIOVASCULAR HEALTH IN A CHANGING CLIMATE: ENVIRONMENTAL RISK FACTORS AND IMPLICATIONS FOR PREVENTION

Abstract

Introduction: Climate-related thermal stress may affect cardiovascular healthcare demand; however, evidence from Pakistan is limited. This study investigated the associations between ambient temperature, acute cardiovascular admissions, in-hospital mortality, and length of stay in Lahore, highlighting implications for healthcare preparedness. Methods: A retrospective multicenter observational time-series study was conducted, analyzing 12,917 admissions among adults aged 20 years and older at three Lahore hospitals from 2023 to 2025. Hospital-specific quasi-Poisson distributed lag nonlinear models estimated cumulative temperature–admission associations over 0 to 21 days, adjusting for seasonality, relative humidity, rainfall, and calendar effects. Estimates were pooled using multivariate random-effects meta-analysis. Adjusted admission-level models evaluated mortality and length of stay among survivors. Results: Acute coronary syndrome comprised 48.3% of admissions, acute decompensated heart failure 31.9%, and arrhythmia 19.8%. Low temperature was not significantly associated with total admissions (RR 1.27, 95% CI 0.71 2.27; p=.418). The estimated minimum-risk temperature matched the high-temperature comparison, so we could not estimate an independent heat-risk effect for total admissions. Extreme-heat days (RR 1.00, 95% CI 0.91–1.10) and heatwaves (RR 1.04, 95% CI 0.93–1.16) were not clearly associated with admissions. Each 5°C increase in admission day mean temperature corresponded to a 2% longer expected hospitalization among survivors (adjusted mean-stay ratio 1.02, 95% CI 1.01–1.03; p<.001), while mortality findings remained inconclusive (adjusted OR 1.04, 95% CI 0.92–1.16). Subgroup and sensitivity analyses were also inconclusive. Conclusion: Higher admission-day temperatures were associated with modestly longer hospitalizations among survivors, while associations with admissions and mortality remained uncertain. Imprecise estimates and boundary reference temperatures limited the strength of inferences. The study did not establish climate-change attribution or preventive effectiveness.