Quadrupling of heat-attributable cardiovascular deaths by 2050 across 471 cities in south and southeast Asia: urban greening could prevent 32,000 deaths

Background Extreme heat intensifies cardiovascular disease (CVD) mortality in urban heat islands (UHI). Climate change threatens to amplify this burden, yet comprehensive assessments are absent for rapidly urbanising Global South regions. We modelled urban greening impacts on heat-attributable CVD in South and Southeast Asia, a region of >2 billion people, where rapid urbanisation, dense populations and diminishing green space increase heat-attributable CVD risk. Purpose To quantify heat-attributable CVD deaths at baseline and 2050 under different climate scenarios and model how urban greening could mitigate this burden. Methods We analysed 471 (779 million residents) of the 500 most populous cities in South and Southeast Asia using high-resolution (100m) satellite data across 15 countries. City-specific relationships between land surface temperature (LST) and normalised difference vegetation index (NDVI) were fitted, controlling for building height, topography and distance-to-water to estimate cooling efficiency (NDVI-regression coefficient). Climate zone-specific regression models converted LST change to air temperature change. Heat-attributable CVD deaths were estimated for baseline (2016-23) and 2050 under SSP2-4.5 (moderate) and SSP5-8.5 (high) emission scenarios using published climate zone-specific temperature-mortality impact. Two scenarios (+0.05 and +0.10 NDVI units; about +10-20pp greening) were modelled, with preventable deaths estimated as difference between baseline and post-greening estimates. Uncertainty was quantified by 1,000 Monte Carlo simulations. Results Heat contributed to 33,172 [95% CI: 22,317-44,494] annual CVD deaths at baseline (3.3 per 100,000). By 2050, deaths increase 3.3-fold under SSP2-4.5 (109,637 deaths; 10.8 per 100,000) and 3.9-fold under SSP5-8.5 (130,799 deaths; 13.3 per 100,000) (Figure 1), exceeding projections for high-income nations. Regional vulnerability changed considerably: under SSP5-8.5, Southeast Asian cities face 767% increases (21.2 per 100,000) vs 168% in South Asia (9.5 per 100,000). Moderate greening (+0.05 NDVI) may prevent ~20% of baseline deaths (6,622) and ~15% of 2050 SSP5-8.5 deaths (16,668) (Figure 2). Aggressive greening (+0.10 NDVI) may prevent ~35% of baseline (11,671) and ~25% of 2050 deaths (32,928). Benefits seemed to scale with climate severity: Southeast Asian cities have greater preventable death rates (4.4 vs 2.3 per 100,000 for +0.05 NDVI). The highest preventable death rates among the 50 most populous cities (2050, SSP5-8.5, +0.10 NDVI) were in Yangon (9.6 per 100,000) and Mumbai (8.0 per 100,000). Conclusion UHI effects may quadruple heat-attributable CVD mortality by 2050 across analysed cities in Asia. Strategic urban greening could prevent up to 25% of this burden. This shows CVD prevention must expand beyond efforts to control conventional risk factors to structural environmental interventions through coordinated urban planning and policy action.Figure 1:Heat-CVD Deaths 2050 (SSP5-8.5)