Netherlands: Heatwaves caused minor rise in mortality

During the recent heatwaves of this summer, there were 2,714 deaths per week on average. This is around 100 deaths more than during an average week in the summertime. Despite the rise in mortality, the additional number of deaths is relatively low. The long heatwave in the summer of 2006 caused mortality to rise by almost 400 per week. Statistics Netherlands (CBS) reports this based on preliminary weekly mortality rates.

There have been two nationwide heatwaves in 2018: from 15 through 27 July and from 29 July through 7 August. Likewise, 2006 had two heatwaves: from 30 June through 6 July and from 15 through 30 July. The second heatwave of 2006 lasted 16 days, one of the longest and most intense in over a century. An additional two short-lived heatwaves were recorded by the Royal Netherlands Meteorological Institute (KNMI) in De Bilt: one in 2013 lasting seven days and one in 2015 which lasted six days.

More deaths as temperature rises

Previous research conducted by CBS and the Netherlands Interdisciplinary Demographic Institute (NIDI) has indicated a correlation between high temperatures and increased mortalities. During the two consecutive heat waves in July 2006, there were an additional estimated one thousand deaths compared to an average month of July. 

Although this year has had two heat waves, mortality did not increase significantly. Nowadays, there is more awareness of what to during a heat wave. Furthermore, a long spell of cold weather this past spring sparked an influenza epidemic, which caused a higher number of premature deaths.

Higher mortality among elderly people in particular

The heat affected the oldest part of the population most seriously. The additional deaths were mainly among people aged 80 years and over. During the heatwaves of 2018, the number of deaths among this age group was 1,500 per week on average, almost the same number as during the heatwave of 2006 (1,536). However, the total number of over-80s in the population increased from 590 thousand on 1 January 2006 to 780 thousand on 1 January 2018. 

Relatively speaking, mortality was therefore much lower in 2018 than in 2006, but it was higher than during a normal week in summertime. In 2018, on average 193 persons per 100 thousand inhabitants aged 80 years or older died per week in week 29, 30 and 31. This was 262 in the weeks of the heatwave in 2006 (week 27. 29 and 30). In the same weeks in 2015 to 2017, 183 persons died per 100 thousand inhabitants per week who were aged 80 or older. 

Compared to the same period in previous years, as well as the heatwave in 2006, a relative decline was seen instead in mortality among the age groups 65 to 79 years and 0 to 64 years.