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The role of temperature and atmospheric pressure in heart failure deaths

HeartFailureExposure to cold or high-pressure weather could trigger events leading to hospitalisation or death in heart failure patients, found a Canadian study. The authors of the study say elderly with heart failure should avoid fog and low cloud in the winter as a preventive measure.

Previous research has shown that changes in the weather can affect the health of vulnerable people – for example, heat waves and cold spells have been shown to increase disease and even lead to death in people from low-income neighborhoods.

The new study, led by researchers at Université Laval and Université de Sherbrooke in Quebec, Canada, reveals the impact of changes in temperature and air pressure on heart failure patients. "We know that doctors rarely take the weather forecast into account when treating or making recommendations to heart failure patients," said Professor Pierre Gosselin, lead author of the study from Universitié Laval. "So with the extreme differences in temperature due to climate change, we wanted to show how the weather is becoming a more relevant factor. Our study shows that exposure to cold or high-pressure weather could trigger events leading to hospitalization or death in heart failure patients."

Treating heart failure patients is expensive: according to the Institut Canadien d'Information sur la Santé, people over 65 accounted for 78% of patients with the most expensive hospitalisation costs per diagnosis between 2011 and 2012 in Canada. Of these, the cost of heart failure ranked third and was estimated at CAN$276m.

In the new study, the team assessed 112,793 people aged 65 years and older that had been diagnosed with heart failure in Quebec between 2001 and 2011. Patients with heart failure were identified in the Quebec Integrated Chronic Disease Surveillance System (QICDSS) database using the International Classification of Diseases (ICD). The participants were followed for an average of 635 days. During this time, the researchers measured the mean temperature, relative humidity, atmospheric pressure and air pollutants in the surrounding environment and studied the data to see if there was an association.

The results showed a higher risk of hospitalisation or death in the winter period of the year (October to April) compared to the summer period (May to September). The researchers noticed that the risk to experience hospitalisation or death of heart failure cause was increased of 0.7% for every 1°C decrease in the mean temperature of the previous seven days. They also found that the risk of heart failure incident increased by 4.5% for each increase of 1 kPa in atmospheric pressure.

In other words, a drop of 10°C in the average temperature over seven days, which is common in several countries because of seasonal variations, is associated with an increased risk in being hospitalised or dying of heart failure of about 7% in people aged over 65 diagnosed with the disease.

During the follow-up period, 21,157 heart failure events occurred, representing 18.7% of the people studied. In total, 18,309 people were hospitalised and 4,297 died. In some cases, hospitalisation and death occurred the same day. The researchers calculated this to 0.03% of patients experiencing an incident per day, which extends to about 1,500 hospitalisations or deaths over a 10-year period, or 150 events per year.

Gosselin and the team suggest that elderly with heart failure should be given support and access to preventive measures, especially since managing heart failure is expensive for society. He commented: "Our study suggests that exposure to cold or high-pressure weather could trigger events leading to hospitalisation or death in heart failure patients. This means that they should avoid exposure to fog and low cloud weather in winter as they often accompany high pressure systems."

Background: There are limited data on the effects of climate and air pollutant exposure on heart failure (HF) within taking into account individual and contextual variables.
Objectives: We measured the lag effects of temperature, relative humidity, atmospheric pressure and fine particulate matter (PM2.5) on hospitalizations and deaths for HF in elderly diagnosed with this disease on a 10-year period in the province of Quebec, Canada.
Methods: Our population-based cohort study included 112,793 elderly diagnosed with HF between 2001 and 2011. Time dependent Cox regression models approximated with pooled logistic regressions were used to evaluate the 3- and 7-day lag effects of daily temperature, relative humidity, atmospheric pressure and PM2.5 exposure on HF morbidity and mortality controlling for several individual and contextual covariates.
Results: Overall, 18,309 elderly were hospitalized and 4297 died for the main cause of HF. We observed an increased risk of hospitalizations and deaths for HF with a decrease in the average temperature of the 3 and 7 days before the event. An increase in atmospheric pressure in the previous 7 days was also associated with a higher risk of having a HF negative outcome, but no effect was observed in the 3-day lag model. No association was found with relative humidity and with PM2.5 regardless of the lag period.
Conclusions: Lag effects of temperature and other meteorological parameters on HF events were limited but present. Nonetheless, preventive measures should be issued for elderly diagnosed with HF considering the burden and the expensive costs associated with the management of this disease.

Alain Vanasse, Denis Talbot, Fateh Chebana, Diane Bélanger, Claudia Blais, Philippe Gamache, Jean-Xavier Giroux, Roxanne Dault, Pierre Gosselin

[link url=""]Elsevier material[/link]
[link url=""]Environmental International abstract[/link]

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