Flu makes people six times more likely to suffer a heart attack or stroke in the three days following an infection, new research suggests.
The virus substantially increases sufferers risk of a heart attack for up to a week and stroke for up to one month after they become infected, the research adds.
Suffering from a respiratory infection, which can also include pneumonia, causes inflammation, which can lead to blood clots and subsequent cardiovascular events, a study found today.
To put the findings into context, lead researcher Dr Charlotte Warren-Gash, from the London School of Hygiene & Tropical Medicine, said: ‘In Scotland, among those aged 75 years and above, around two in 10,000 people have a heart attack each week.
‘Our analysis found this figure rose to 10 in 10,000 in the week after having a respiratory infection.’
Researchers believe their findings highlight the importance of being vaccinated against flu and pneumonia, particularly among vulnerable people, such as the elderly or those with pre-existing heart problems.
The life-threatening Aussie flu epidemic earlier this year contributed to NHS bosses making the unprecedented decision to cancel 55,000 operations to cope with the so-called winter crisis.
Flu makes people six times more likely to suffer a heart attack or stroke (stroke)
WHAT FLU STRAINS ARE IN THE UK IN 2018?
There are many different types of flu circulating around the world, but four main types are being seen in Britain this winter.
H3N2 – Dubbed ‘Aussie flu’ after it struck Australia hard last winter, this strain is more likely to affect the elderly, who do not respond well to the current vaccine. This is one of the most common strains seen so far this winter, with at least 63 confirmed cases seen in official laboratories.
H1N1 – This strain – known as ‘swine flu’ – is generally more likely to hit children, who respond well to vaccination. This has been seen nearly as often as H3N2 so far this year, with at least 50 cases confirmed in labs. In the past it was commonly caught from pigs, but that changed in 2009 when it started spreading rapidly among humans in a major global pandemic.
B / Yamagata – This is known as ‘Japanese flu’. Only people who received the ‘four strain’ vaccine – which is being slowly rolled out after it was introduced for the first time last winter – are protected against the Yamagata strain. Those who received the normal ‘three strain’ vaccine are not protected. This strain has been seen in at least 63 lab cases so far this winter.
B / Victoria – This strain is vaccinated against in the normal ‘three strain’ vaccine, but has hardly appeared so far this winter, with just around four confirmed cases.
Understanding who is at risk may lead to interventions
Dr Warren-Gash said: ‘Heart disease, strokes and lower respiratory infections have been the three leading causes of death globally for over 15 years, and are important public health problems that affect large numbers of people worldwide.
‘As people age, having more than one medical condition becomes more common, so it is even more important to understand the links between different diseases.
‘If we can understand who is at risk of these cardiovascular complications after respiratory infections, we can potentially intervene to prevent them, with methods such as vaccines.’
Results further suggest the cardiovascular risks of respiratory infections are greatest in those over 65.
Dr Warren-Gash added: ‘For most young, healthy people, the risk of heart attacks and strokes occurring after a respiratory infection is low.
‘This research is particularly relevant for those over the age of 65, as well as people with pre-existing heart diseases, as these groups are at higher risk of heart attacks and strokes.’
The findings were published in the European Respiratory Journal.
Highlights the importance of vaccinations
The study did not assess less common respiratory infections or how they specifically affect people of different ages.
Dr Warren-Gash said: ‘Our research highlights the importance of ongoing work into which doses of vaccine are best to protect people from heart attacks and strokes.
‘Although flu and pneumonia seem to have the biggest impact, this research also shows that a group of other respiratory viruses had some triggering effects.
‘We don’t currently have vaccines for these viruses so further research is needed.’
Suffering from a respiratory infection, which can also include pneumonia, causes inflammation, which can lead to blood clots and subsequent cardiovascular events (stock)
How the research was carried out
The researchers analysed national infection surveillance data from the Scottish Morbidity Record.
They identified 1,227 adults who had suffered their first heart attack and 762 who had one stroke, as well as a respiratory bacterial or viral infection, between 2004 and 2014.
The rate of cardiovascular events in the stages immediately after a respiratory infection were compared against those that occurred at other times.