Fatal heart attacks more common on a Monday, research suggests; scientists unable to fully explain 'Blue Monday' phenomenon.

The study found that the likelihood of a heart attack occurring on a Monday was 13% greater than expected.

Doctors at the Belfast Health and Social Care Trust and the Royal College of Surgeons in Ireland analysed data from 10,528 patients across the island of Ireland – 7,112 in the Republic and 3,416 in Northern Ireland. They had been admitted to hospital between 2013 and 2018 with the most serious type of heart attack – an ST-segment elevation myocardial infarction (STEMI) which takes place when a major coronary artery is completely blocked.

The researchers found a spike in STEMI heart attacks at the start of the working week, with rates highest on a Monday. There were also higher than expected rates on a Sunday, according to the findings presented at the British Cardiovascular Society (BCS) conference in Manchester.

Scientists have been unable to fully explain this “Blue Monday” phenomenon. Previous studies suggesting heart attacks are more likely on a Monday highlighted an association with circadian rhythm – the body’s sleep or wake cycle.

According to the British Heart Foundation (BHF) there are more than 30,000 hospital admissions due to STEMI each year in the UK. The attack requires emergency assessment and treatment to minimise damage to the heart, normally performed with emergency angioplasty – a procedure to reopen the blocked coronary artery.

Cardiologist Dr Jack Laffan, who led the research at the Belfast Health and Social Care Trust, said: “We’ve found a strong statistical correlation between the start of the working week and the incidence of STEMI. This has been described before but remains a curiosity. The cause is likely multifactorial, however, based on what we know from previous studies, it is reasonable to presume a circadian element.”

Professor Sir Nilesh Samani, medical director at the BHF, said: “Someone is admitted to hospital due to a life-threatening heart attack every five minutes in the UK, so it’s vital that research continues to shed light on how and why heart attacks happen. This study adds to evidence around the timing of particularly serious heart attacks, but we now need to unpick what it is about certain days of the week that makes them more likely. Doing so could help doctors better understand this deadly condition so we can save more lives in future.”