London, June 5 : Fatal heart attacks are more likely to happen at the start of the working week than at any other time, according to new research. The study, presented at the British Cardiovascular Society (BCS) conference in Manchester, UK, found that the likelihood of a heart attack occurring on a Monday was 13 per cent greater than expected. Doctors at the Belfast Health and Social Care Trust and the Royal College of Surgeons in Ireland analysed data of 10,528 patients across the island of Ireland (7,112 in the Republic of Ireland, 3,416 in Northern Ireland) admitted to hospital between 2013 and 2018 with the most serious type of heart attack known as an ST-segment elevation myocardial infarction (STEMI). STEMI occurs when a major coronary artery is completely blocked. The researchers found a spike in rates of STEMI heart attacks at the start of the working week, with rates highest on a Monday. There were also higher rates of STEMI than expected on a Sunday. Scientists have so far been unable to fully explain why this "Blue Monday" phenomenon occurs. Previous studies suggesting that heart attacks are more likely on a Monday have highlighted an association with circadian rhythm -- the body's sleep or wake cycle. "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," said Dr Jack Laffan, a cardiologist who led the research at the Belfast Health and Social Care Trust. "The cause is likely multifactorial, however, based on what we know from previous studies, it is reasonable to presume a circadian element," he added. STEMI requires emergency assessment and treatment to minimise damage to the heart, and this is normally performed with emergency angioplasty -- a procedure to re-open the blocked coronary artery. "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," said Professor Sir Nilesh Samani, Medical Director at the British Heart Foundation (BHF). /IANS