There is an increase in the number of heart disease or heart attack deaths during the annual flu season for people aged 65 or older.
Does flu season, or, more correctly does contacting the flu, have an effect on heart conditions? Researchers from Columbia University, NY, Dept. of Environmental Health Sciences, and the New York City dept. of Health & Hygiene collaborated to determine just that. A study submitted to the Journal of the American Medical Association in Feb. 2016 utilized statistics from NYC’s municipal Dept. of Vital Statistics to determine mortality from heart disease or heart attacks during the annual winter flu season. The goal was to determine if a person with heart disease or heart attack history is more likely to suffer cardiac arrest after experiencing an Influenza-like Illness (ILI). Influenza, as defined by Health Canada, is a virus that causes an infection of the nose, throat, and lungs, and is highly contagious. It has previously been reported that the flu viruses can cause direct cardiac changes, ranging from no symptoms to abnormalities in a person’s heart’s electrical changes. The flu virus also impacts a body systemically by causing the release of inflammatory cytokines (tiny proteins that signal cells to release inflammatory agents) and cause changes in some clotting patterns.
This research study utilized a Time-Series Analysis method (a method of research that looks at and analyzes groups of data that occur over time, eliciting patterns), and looked at 73,336 causes of cardiovascular deaths during influenza seasons from 2006-2012. Researchers then investigated whether or not the individual in question had presented with ILI symptoms in the past 21 days. The H1N1 flu period was excluded from results (2009/2010). The authors investigated all deaths that occurred during flu season, and gathered information such as date of death, age, & the etiology of death from NYC’s statistics department. The authors included cases where the cause of death was heart disease and/or heart attack. Emergency Department data was also utilized in order to obtain a history on whether or not the person had reported ILI symptoms in the past 21 days. This time series analysis method also included isolating variables such as temperature, relative humidity, day of the week trends, and looking at the number of emergency department (ED) visits for specific strains of the flu virus. Between 2006 and 2016 (again, not the H1N1 time period), cardiovascular disease among people 65yrs or older accounted for 83% (the studies’ participant number was 73363) of mortalities.
The results indicated that the timing of these deaths showed a strong seasonal timeline trend, that corresponded with flu season. This means that there was a noticeably higher mortality rate for elderly persons during flu season which reduced to baseline at the conclusion of that year’s flu season. These results support the concept that there is a greater impact of influenza virus on people over 65 than others that are younger. For example, the article states that for every 102 extra ED visits for ILI (so, any extra 102 persons going to the ED for flu like symptoms compared to non-flu season times) there would be a 6-7% increase in deaths due to heart disease. The strongest link was between flu virus and heart attacks. Interestingly, a decrease in absolute humidity (think of those really cold, dry winter days) also correlated with a 3% increase in heart disease mortality. Limitations of the study included only people that had visited an ED for their symptoms. Some of the illnesses may not have been reported, or those minor symptoms may have not sought out medical attention. Thus, this study only reflects data from assumedly moderate or severe symptomatic individuals.
The knowledge that cardiovascular disease sufferers are at a significantly greater risk of mortality after an influenza exposure is very important for patients, families, care-givers, and the health care system at large. It enforces the need for everyone to remember proper hand hygiene, self-screen for illnesses before visiting a vulnerable friend or family member or other public place, getting your flu shot as recommended by your physician, and taking steps to ensure a positive state of health prior to the annual flu season to prevent disease transmission. Prevention, in this case, could really be the best medicine. For health care providers and the health system, being able to predict when there will be an increase in patients, and the types of patients, can assist with planning of resources and completing proper staff training prior to the actual outbreak. According to this study’s authors, it is possible to predict cardiovascular mortality during a flu season with 94% accuracy – quite a feat in terms of planning and preventative medicine. The influenza virus is not the only factor of cardiovascular-related mortality. Things like fat intake, activity level, stress level, and even some hemostatic variables out of our control, change in the winter months. It is the holiday season, and the former of the above factors are definitely affected by the festivities. However, a link between contracting a flu virus and its effect on individuals with heart conditions cannot be ignored.
Written By: Tori Cuthbertson, BSc AEMCA