Mortality and temperature in Sofia and London

Area of Science:

• Environmental epidemiology
• Public health
• Biometeorology

Background:

• Extreme temperatures (heat and cold) are linked to increased mortality, but detailed understanding remains limited.
• Previous research indicates mortality increases independently of seasonal patterns, necessitating further investigation into specific temperature-mortality relationships.

Purpose of the Study:

• To investigate the associations between daily mortality and ambient temperature in two distinct European capitals: Sofia and London.
• To analyze the impact of both extreme cold and heat on all-cause mortality over four-year periods.

Main Methods:

• Utilized generalized additive models to analyze daily deaths, air pollution, and weather data from Sofia (1996-1999) and London (1993-1996).
• Employed non-linear modeling for confounders like season and humidity, assessing temperature-mortality relationships using two-day and two-week averages.
• Estimated lag effects, linear effects, and attributable fractions for heat and cold.

Main Results:

• Extreme cold (below 10th centile) increased mortality by 4.2% per degree in London and 1.8% in Sofia.
• Heat (above 95th centile) increased mortality by 1.9% per degree in London and 3.5% in Sofia.
• Cold effects manifested around three days lag and persisted for at least two weeks, especially in London; heat effects were more immediate.

Conclusions:

• Short-term average temperatures may not fully capture the impact of cold, and potentially heat (due to harvesting effects).
• Cold temperatures pose a significant risk to the general population in London, with effects not limited to those nearing death.
• Findings underscore the public health impact of temperature extremes and the need for tailored environmental health strategies.