Heatwaves in Norway and impacts on public health: Need for Heat Action Plans

We indicate the future need for heat action plans in Norway that account for public health. They will need to include alert systems, working with service providers and engaging the community.

Background: Extreme temperatures, both hot and cold, increase death rates and can exacerbate a range of diseases. Older people, >65 years of age, suffer disproportionally more than younger people during extreme temperature events. The Meteorological Institute of Norway has released new definitions of heatwaves in Norway and these indices are currently being tested. Using historical data from the EU EXHAUSTION project we test the impact of these heat waves on mortality and morbidity for these heat waves and make recommendations on heat wave plans.

Methods: The data covers Oslo, Bergen, Trondheim, and Tromsø in the 2008-2018 period. We used daily mortality counts for natural mortality provided by the Norwegian Death Registry and hospital admissions from the Norwegian Patient Registry. Counts were also available stratified by age (0-74, 75-84, 85+) and sex. We used city level temperature data from the meteorological institute. We used Poisson regression models to model the death counts in response to periods of heat. Given that many of our variables are related, we did univariate analyses looking at one heat wave index at a time. We repeated the same analyses stratified by sex and age group.

Results: Initial results indicate that periods of heatwaves tend to be followed by an increase in death. We particularly see an increased risk of mortality of up to 2.5 times more for periods with continuous five days maximum temperature of 28 degrees C and minimum temperature below 16 degrees C. The effect is also seen to be stronger in women and in older people.

Discussion: These results are relevant for developing heat action plans that target vulnerable populations in Norway. This is especially important as we see increasing heat episodes in Norway in the next three decades and preparing such plans will be essential. An increase in aging populations in Norway in the future will mean increasing impacts for the elderly and a need for including all vulnerable groups in the plans. We forecast that such plans need to include alert systems (advance warning and advice over the summer), working with service providers and engaging the community.