Abstract Body (Do not enter title and authors here):

Introduction:
Extreme heat events pose increasing risks for cardiovascular mortality. This study examined trends in cardiovascular deaths associated with heat-related illness in the United States from 1999 to 2020.
Hypothesis:
We hypothesized that cardiovascular mortality associated with heat-related illness increased from 1999 to 2020, with significant disparities across age, sex, race, region, and urbanization, reflecting disproportionate climate vulnerability among at-risk populations.
Methods:
Mortality data from CDC WONDER (1999–2020) were analyzed. Death listings for both cardiovascular disease (I00–I99) and heat-related illness (T67, R53, R55) were included. We used the 2000 U.S. standard population to generate age-adjusted mortality rates (AAMRs) per 100,000. Joinpoint regression calculated the annual and average annual percentage change (APC and AAPC). Stratified analyses were conducted by race/ethnicity, age, sex, region, and urban/rural status. A significance level of p < 0.05 was used.
Results:
From 1999–2020, 121,600 heatwave-related cardiovascular deaths occurred. AAMR rose from 1.76 to 2.27. In 1999, the South had the highest AAMR (2.02), Northeast the lowest (1.29); in 2020, the Midwest was highest (2.59), Northeast remained lowest (1.45). Black individuals had the highest AAMR in both 1999 (2.50) and 2020 (2.43), Asians the lowest (1.05; 1.43). Rural mortality exceeded urban in both years (2.00 vs 1.71 in 1999; 2.34 vs 2.24 in 2020). Males had higher AAMRs than females (1.87 vs 1.63 in 1999; 2.44 vs 2.06 in 2020). The West showed the largest increase (AAPC: 2.42%; 95% CI: 0.29–4.61); the South had the smallest, nonsignificant change (AAPC: 0.23%; 95% CI: –0.51–0.97). American Indians showed the largest decline (AAPC: –4.81%; 95% CI: –7.94–1.58), Whites the greatest rise (AAPC: 1.25%; 95% CI: 0.10–2.41). Urban areas had a higher AAPC (1.26%) than rural (0.71%). Males showed a significant increase (AAPC: 1.31%; 95% CI: 0.39–2.23), females nonsignificant (AAPC: 1.05%; 95% CI: –0.73–2.87). Age 35–44 had the lowest mortality (0.11 in 1999; 0.06 in 2020) and declined (AAPC: –3.75%; 95% CI: –4.70–2.78); 85+ had the highest (38.20 and 48.99). The largest increase was in age 55–64 (AAPC: 2.14%; 95% CI: 1.50–2.78); smallest in 45–54 (AAPC: 0.33%; 95% CI: –0.59–1.26).
Conclusion:
Cardiovascular deaths linked to heatwaves rose over two decades, affecting older adults, men, and Western states most, while American Indians and younger adults showed improvement.