Seasonal Variations in Mortality Caused by Cardiovascular Diseases in Norway and Ireland

Abstract

Background Seasonal variations in mortality resulting from cardiovascular diseases (CVD) have been demonstrated in many countries, with the highest levels observed during the coldest months of the year. We studied the seasonal changes in CVD mortality in Norway and the Republic of Ireland, two countries which are demographically quite similar, but climatically different; we also examined the relation between CVD mortality and air temperature.Methods Registered monthly data for mortality from CVD for the period 1985-1 995 were obtained from the Norwegian Central Bureau of Statistics and the Irish Central Statistics Office. Meteorological data were provided by the Norwegian Institute of Meteorology and Met Eireann, in Ireland. Monthly mortality ratio for both men and women aged 60 and older was calculated from the mortality date. Mean monthly air temperatures for the two countries were calculated from the meteorological data. ResultsFor the 1 0-year period investigated, the lowest and highest monthly mortality ratios were on average found in August and January, respectively, and mean excess winter mortality, expressed as the difference between the August and January values for the entire 1 0-year period, was 22% (Norway) and 35% (Ireland). However, when the percentage difference in the months with the respective highest and lowest mortality ratios were calculated for each year, the average of these differences for each of the 10 individual years was 29% and 45%. Mortality ratio was found to increase much more steeply with decreasing air temperature in Ireland than in Norway. ConclusionAlthough the seasonal variation between CVD mortality in both countries is similar, the different relation with climatic conditions may result from differences in housing standards, allowing outdoor temperatures to have a greater influence on indoor temperature in Ireland than in Norway.

Weekly pattern of emergency room admissions for peptic ulcers: A population-based study

“…Numerous studies have investigated diurnal, weekly, or seasonal variations in the onset of different diseases, such as cardiovascular diseases [7,[22][23][24] , cerebrovascular diseases [25,26] , and psychiatric disorders [27][28][29] , as well as complicated (including hemorrhage and perforation) and uncomplicated PUs [8][9][10][11] , for which the highest incidences are in winter. This seasonal fluctuation of PU may be affected by several factors, including climatic factors [30] , increased intake of NSAIDs in winter [31] , significantly increased number of H. pylori infections in winter [32] , and variations in alcohol consumption [33] .…”

Effects of the thermal environment on human health: an investigation of 30 years of daily mortality data from SW Germany

“…It is assumed that some of these seasonal variations in mortality can be ascribed to the effects of outdoor air temperature (Kunst et al 1993, Saez et al 1995, Laake & Sverre 1996, Eng & Mercer 1998, Lerchl 1998, Pell & Cobbe 1999. The relation of mortality data to thermal conditions shows a typical seasonal pattern with a maximum in February and a minimum in August (Sakamoto-Momiyama 1977).…”

“…This suggests that people die who would have died in the short term anyway ('mortality displacement'; Alberdi 1998). On the other hand, a proportion of the additional mortality during extreme heat also concerns avoidable deaths and is consequently combined with a considerably diminished longevity (Eng & Mercer 1998).…”

“…This suggests that people die who would have died in the short term anyway ('mortality displacement'; Alberdi 1998). On the other hand, a proportion of the additional mortality during extreme heat also concerns avoidable deaths and is consequently combined with a considerably diminished longevity (Eng & Mercer 1998).Mortality rates and thermal stress seem to be more closely linked in summer than in winter (Kalkstein & Greene 1997), because in summer there is often more direct exposure to outdoor conditions than in winter. Moreover, other effects, such as a higher risk of infection, partly reflect the relation in winter.…”

Seasonality of climate-human mortality relationships in US cities and impacts of climate change

“…Although many different causes of death exhibit this seasonality, cardiovascular and respiratory mortality seasonal variations have garnered the most attention (Donaldson et al 1998, Eng & Mercer 1998, Danet et al 1999, Kloner et al 1999, Lanksa & Hoffmann 1999, Pell & Cobbe 1999, McGregor 2001, McGregor et al 2004). The seasonal component so dominates the long-term signal that it is even evident in plots of daily data.…”