Elderly patients with a history of cardiovascular disease might want to limit outdoor activities this winter season, according to a group of researchers in Quebec. Their recent study showed that risk of heart failure in older populations can increase as temperature drops.
Climate change—extreme temperatures, extended heat waves and cold snaps—can have various negative health effects in vulnerable populations, including poorer demographics, people living with chronic disease and elderly individuals, lead researcher Pierre Gosselin, MD, and colleagues wrote in the study. But the team wanted to extend research to include the effects of atmospheric pollutants, fine particulate matter (PM) and relative humidity on cardiovascular disease and heart failure.
The researchers used the Quebec Integrated Chronic Disease Surveillance System to build a cohort of 112,793 elderly heart failure patients, all 65 years of age or older, who were diagnosed with cardiovascular disease between 2001 and 2011. Time-dependent Cox regression models were used to approximate three- and seven-day lag effects of daily temperature, humidity, PM exposure and atmospheric pressure on heart failure morbidity and mortality in the subjects, who were all living in the Canadian province at the time.
Though most patients—44.2 percent—were concentrated in the Montreal area, Gosselin and colleagues spread their research across Quebec, which sees average temperatures ranging from negative-16 degrees Celsius in the winter to 20 degrees Celsius in the summer. Patients were also pooled from other census metropolitan areas and rural regions.
Most individuals had cardiovascular risk factors prior to Gosselin’s study, with just over 60 percent of the total population recorded as suffering from hypertension at baseline, according to the research. A smaller percentage—just 32 percent—of individuals identified as diabetic.
The study’s authors followed patients for an average of 635 days during a decade and found that 18.7 percent of the study cohort were hospitalized for heart failure events during that time. Of a total 21,157 heart failure events, 4,297 individuals died and 18,309 patients were hospitalized. This translated to a daily incidence rate of 0.03 percent, Gosselin and colleagues wrote.
The study stated average temperature and risk of negative heart failure outcomes corresponded linearly, with heart failure risk increasing as temperature dropped. For every decrease of 1 degree Celsius in temperature, the risk of heart failure increased by 0.7 percent, the authors wrote, which means a 10-degree drop in temperature over a weeklong period—not uncommon in Quebec—could result in a 7 percent increase in cardiovascular risk in the vulnerable elderly population. These conclusions were reached after considering several individual and contextual covariates, like existing cardiovascular risk factors and medications, the authors noted.
Gosselin and colleagues also found that for every change of 1 kPa in atmospheric pressure at sea level, risk for heart failure events increased by 4.5 percent in their seven-day lag model. High pressure is often accompanied by fog and low clouds in wintertime, the authors wrote, which can be dangerous conditions for at-risk patients. They found no correlation between daily relative humidity and acute risk of heart failure.
Although the relative risk of heart failure events in conjunction with colder temperatures didn’t show a strong correlation, the researchers said they’d still recommend avoiding chilly conditions to older individuals who have been treated for cardiovascular disease in the past.
“We think that preventive instructions should be provided to individuals with this disease, especially since its management is expensive for the society,” they wrote. “In 2011 and 2012 in Canada, elderly accounted for 78 percent of the patients with the most expensive hospitalization motives per diagnosis in short-term care; heart failure was ranked third, with costs estimated to [$223 million].
“To our knowledge, this is the first study of its kind performed in Canada. It paves the way to the realization of further studies to support the surveillance of chronic cardiovascular diseases in a context of climate changes.”