Projected heat- and cold-related mortality in Taiwan under climate and population change

Objectives

Reliable estimates of future health impacts due to climate change are essential for designing effective adaptation and mitigation strategies. This study aims to quantify heat‑ and cold‑related mortality in Taiwan across counties, age groups, and disease categories, and to establish an epidemiological framework for future mortality projections under climate and demographic change.

Material and Methods

County-specific temperature–mortality associations were estimated for all counties in Taiwan using daily mortality counts by age group and meteorological observations (1998–2022), modelled via distributed lag non‑linear models (DLNMs). County-specific estimates were pooled via multivariate meta-analysis to derive overall exposure–response relationships.

Results

Across 14 counties and 6 disease categories, cold temperatures were the dominant driver of current temperature-attributable mortality. The minimum mortality temperature was approximately 22–23 °C. Cold exposure (10th percentile, ∼13 °C) was associated with a 42% higher all-cause mortality risk (RR 1.42, 95% CI 1.36–1.48), while heat (90th percentile, ∼27 °C) conferred a 10% excess risk (RR 1.10, 95% CI 1.07–1.13). Cold accounted for 9.7% (95% CI 8.5–10.5%) of all-cause deaths and heat for 3.4% (95% CI 2.6–4.0%), yielding a total temperature-attributable fraction of 13.0% (95% CI 11.9–14.1%). Disease-specific analyses revealed the highest cold risks for nervous system diseases (RR 1.64, 95% CI 1.33–2.01; AF 20.2%, 95% CI 8.7–25.3%). Adults aged 65 and over showed consistently elevated risks across all causes compared to younger adults.

Conclusions

These findings establish robust, pooled temperature–mortality relationships across Taiwan, revealing cold exposure as the dominant driver and older adults as the most vulnerable group. The projection framework, integrating CMIP6 climate and SSP demographic scenarios, will be applied in subsequent analyses to quantify future health burden.

Key messages

• Cold temperatures drive most temperature‑related deaths in Taiwan, outweighing heat impacts, with a minimum mortality temperature around 22-23 °C.

• Older adults (≥65 years) bear the highest temperature‑related mortality risk, highlighting cold‑focused adaptation as a public health priority.