Acute fatal effects of short-lasting extreme temperatures in Stockholm, Sweden: evidence across a century of change.
BACKGROUND
Climate change is projected to increase the frequency of extreme weather events. Short-term effects of extreme hot and cold weather and their effects on mortality have been thoroughly documented, as have epidemiologic and demographic changes throughout the 20th century. We investigated whether sensitivity to episodes of extreme heat and cold has changed in Stockholm, Sweden, from the beginning of the 20th century until the present.


METHODS
We collected daily mortality and temperature data for the period 1901-2009 for present-day Stockholm County, Sweden. Heat extremes were defined as days for which the 2-day moving average of mean temperature was above the 98th percentile; cold extremes were defined as days for which the 26-day moving average was below the 2nd percentile. The relationship between extreme hot/cold temperatures and all-cause mortality, stratified by decade, sex, and age, was investigated through time series modeling, adjusting for time trends.


RESULTS
Total daily mortality was higher during heat extremes in all decades, with a declining trend over time in the relative risk associated with heat extremes, leveling off during the last three decades. The relative risk of mortality was higher during cold extremes for the entire period, with a more dispersed pattern across decades. Unlike for heat extremes, there was no decline in the mortality with cold extremes over time.


CONCLUSIONS
Although the relative risk of mortality during extreme temperature events appears to have fallen, such events still pose a threat to public health.
From the aDepartment of Public Health and Clinical Medicine, Division of Occupational and Environmental Medicine, Umeå University, Umeå, Sweden; bAgeing and Living Conditions Programme, Umeå University, Umeå, Sweden; cCentre for Population Studies, Umeå University, Umeå, Sweden; and dDepartment of Public Health and Clinical Medicine, Division of Epidemiology and Global Health, Umeå University, Umeå, Sweden.
Daniel Oudin
DO
Åström
Bertil
B
Forsberg
Sören
S
Edvinsson
Joacim
J
Rocklöv
D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D055873:Extreme Cold / Q000009:adverse effects*; D055874:Extreme Heat / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009026:Mortality / Q000639:trends*; D012306:Risk; D017678:Sex Distribution; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors; D055815:Young Adult