Heatwaves in cities in Norway and impacts on mortality: Urgent Need for Heat Plans

Abstract Background Heatwaves have been increasing in frequency in Europe, thus activating heat health action plans in many countries. Extreme temperatures increase death rates (mortality) 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 with temperatures over 28 degrees and nighttime temperatures over 16 degrees. Using historical data on temperature and data from the Death Registry in Norway we test the impact on mortality for these heat waves. Methods The data covers Oslo, Bergen, Trondheim, and Tromsø in the 2008-2018 period. We used daily mortality counts for natural mortality over the study period of 1996 to 2018, 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 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 historically periods of heatwaves tend to be followed by an increase in death in urban areas in Norway. The effect seems stronger in women and in older people. Discussion These results are relevant for developing hat action plans that target the 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 for Norway. This work is a joint collaboration between the key health and meteorological institutes in Norway, thus highlighting the role of interdisciplinary collaboration in developing heat health action plans. Key messages • Heatwaves are associated with mortality in Norway. • There is an urgent need for early warning systems and heat health action plans in Norway.