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The effect of temperature on mortality in Stockholm 1998-2003: a study of lag structures and heatwave effects
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.ORCID iD: 0000-0003-4030-0449
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Occupational and Environmental Medicine.
2008 (English)In: Scandinavian Journal of Public Health, ISSN 1403-4948, Vol. 36, no 5, 516-523 p.Article in journal (Refereed) Published
Abstract [en]

AIMS: To describe seasonal patterns of natural mortality in Stockholm as well as the temperature-mortality relationship and the lag structure for effects of high and low temperatures; to describe the impact of high temperatures on cardiovascular and respiratory mortality, and the general effect of high temperatures in different age groups; and to investigate whether there is any indication of an additional heatwave or cold spell effect.

METHODS: Generalized additive Poisson regression models were fitted to mortality and temperature data from Stockholm from the period 1998-2003, controlling for influenza, season, time trends, week day, and holidays.

RESULTS: The mortality in Stockholm followed a seasonal pattern, with a peak in the winter season. The ;;optimal temperature'' was around 11-12 degrees C. Above this temperature, the cumulative general relative risk (RR) corresponded to a 1.4% (95% confidence interval (CI)=0.8-2.0) increase per degrees C, and below this temperature the cumulative RR corresponded to a 0.7% (95% CI=0.5-0.9) decrease per degrees C. Age-specific RRS were estimated above the threshold for age <65 years, age 65-74 years, and age >74 years, with estimated increases of 0.5% (not significant), 1.5% (not significant) and 1.6% (95% CI=0.9-2.3) per degrees C, respectively. The RRs for cardiovascular and respiratory causes were studied above the breakpoint, and estimated to be 1.1% (95% CI=0.3-2.0) and 4.3% (95% CI=2.2-6.5) per degrees C, respectively. The lag structures from moving averages and polynomial distributed lag models coincided with a rather direct effect during summer (lag 0 and 1) and a more prolonged effect during winter, covering about a week. The inclusion of an indicator of heatwaves added an increase in daily mortality of 3.1-7.7%, depending on the threshold.

CONCLUSIONS: These results show that the predicted increase in heat events must also be taken seriously in Scandinavia, whatever the extent of the decreasing cold related mortality. The relative risks associated with heat and heatwaves seem stronger than the cold effects and thus a larger public health threat, since northern populations have not yet adapted to heat as have been done over a long time for the cold periods. The pressure on the healthcare sector will probably increase in the warm season, periodically it may become even greater than the pressure due to cold weather, which will be a new phenomenon for the healthcare sector to cope with. We need to be prepared for these kind of events by developing adaptation and education strategies to handle the consequences that a warmer climate will have for public health and the healthcare sector.

Place, publisher, year, edition, pages
2008. Vol. 36, no 5, 516-523 p.
National Category
Environmental Health and Occupational Health
URN: urn:nbn:se:umu:diva-18792DOI: 10.1177/1403494807088458PubMedID: 18567653OAI: diva2:174771
Available from: 2009-02-25 Created: 2009-02-25 Last updated: 2015-04-29Bibliographically approved
In thesis
1. Short-term effects of ambient temperature on daily deaths and hospital admissions
Open this publication in new window or tab >>Short-term effects of ambient temperature on daily deaths and hospital admissions
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Incidence of death and hospitalizations have been observed to depend on short-term changes in weather and to increase with extreme temperatures. This thesis aims to strengthen the scientific knowledge on the relationship between temperature and daily deaths, but also the relationship between temperature and daily hospital admissions.

Methods: We constructed time series regression models using daily counts of death and daily weather from the Stockholm area incorporating adjustment for potential confounding factors, season, and long-term time trends. From these models, we established the short-term relationship with daily temperatures and the associated relative risks on daily deaths allowing for a delay between exposure and subsequent deaths. Daily hospital admissions and daily temperatures were analyzed correspondingly using data from Skåne.

Results: Hot and cold temperatures significantly impact on mortality rates as well as rates of hospitalization in Sweden. We found an immediate heat effect on daily deaths, while the impacts of cold temperatures were delayed up to a week after exposure. Cold-related deaths are generally cardiovascular in nature, while deaths resulting from warm temperatures are cardiovascular, respiratory as well as non-cardiorespiratory in nature. The impacts following a heat wave appear to increase proportionally with the length of the extreme hot conditions. The results suggest that the population aged 45 years and older is the main group at elevated risk of death when exposed to high and low temperatures. Moreover, the results suggest that there are several factors of susceptibility on an individual basis that correspond to larger relative risk with high and/or low temperatures.

Daily hospitalisations increased in particular among individuals with respiratory illnesses during extreme persistent heat, whereas high temperatures in general have little impact. In contrast, hospitalizations increased for up to two weeks following exposure to cold temperatures.

Conclusions: The health impacts related to temperature are a serious concern and the attributed impacts are likely to increase to some extent in the future due to an ageing population. Public health preventive strategies should be developed to prevent health consequences related to heat waves and cold temperatures. Future studies should aim at identifying susceptible individuals with elevated death risk at hot and cold ambient temperature conditions.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2010. 70 p.
Umeå University medical dissertations, ISSN 0346-6612 ; 1341
temperature, humidity, weather, climate, climate change, hot, heat, cold, cold spell, cold wave, heat wave, health, hospitalization, hospital admission, death, mortality, morbidity, epidemiology, environmental epidemiology, time series
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Research subject
Occupational and Environmental Medicine
urn:nbn:se:umu:diva-32906 (URN)978-91-7264-973-6 (ISBN)
Public defence
2010-04-23, Room 135, Family medicine, Umeå University, Umeå, 13:00 (English)
Available from: 2010-04-01 Created: 2010-03-30 Last updated: 2015-04-29Bibliographically approved

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