The Mortality Response to Absolute and Relative Temperature Extremes.

Area of Science:

• Environmental Health
• Epidemiology
• Climate Science

Background:

• Absolute extreme temperatures' health impacts are well-studied, unlike relative temperature extremes.
• Relative extreme events are unusual for the season but not necessarily extreme overall.
• Recent metrics define absolute and relative extreme heat/cold events.

Purpose of the Study:

• To evaluate all-cause mortality from absolute and relative extreme temperature events.
• To assess immediate and cumulative 20-day mortality impacts across 51 US metropolitan areas.
• To compare heat and cold event impacts, including regional variations.

Main Methods:

• Utilized a distributed lag nonlinear model for mortality analysis (1975-2010).
• Defined absolute extreme heat/cold events (EHE/ECE) and relative extreme heat/cold events (REHE/RECE).
• Conducted meta-analysis across 8 US regions for 51 metropolitan areas.

Main Results:

• Heat events showed immediate mortality increases (0-day lag) with subsequent harvesting.
• Absolute extreme heat events (EHE) had statistically significant 20-day mortality increases.
• Cold events (ECE/RECE) exhibited delayed mortality increases, with significant cumulative impacts for both.
• Relative extreme cold events (RECE) showed significant mortality in southern regions, suggesting acclimatization issues.

Conclusions:

• Relative extreme cold events present a notable public health concern, particularly in areas with less acclimatization.
• Absolute extreme heat events have lasting mortality impacts, while relative heat events show short-term displacement.
• Both absolute and relative cold events contribute to excess mortality, highlighting the need for targeted interventions.