Heart attacks are more dangerous in the morning than at any other time of day, research has shown. The study has shown that compared with other times, patients who had an attack between 6am and noon suffered around 20% more damage to their hearts. Researchers say this pattern is thought to be linked to circadian rhythms, the 24-hour “body clock” processes that influence many biological functions including blood pressure.
A team of Spanish researchers led by Dr Borja Ibanez set out to determine the impact of the time of day when a heart attack happens. They analyzed data on 811 patients admitted to the Hospital Clinico San Carlos in Madrid. They measured the amount of dead heart tissue left by attacks. The size of the dead area, or “infarct”, was calculated by looking at levels of enzymes in the patients. Timing of heart attacks was divided into four six-hour periods running in phase with 24-hour circadian rhythms.
Results showed that patients with the largest infarct size were those whose heart attacks occurred in the dark-to-light transition period between 6am and noon. In total, 269 patients had their heart attack during the morning danger period. Another 240 suffered attacks between noon and 6pm, 161 between 6pm and midnight, and 141 between midnight and 6am.
Judy O'Sullivan, senior cardiac nurse at the British Heart Foundation, said, “This study provides some interesting observations on the association between the time of day a heart attack occurs and the degree of subsequent damage to the heart muscle. However further research is needed before we can draw firm conclusions. Regardless of the time of day, the quicker someone having a heart attack is treated, the less the damage they will have, which is why it is essential that anyone who experiences heart attack symptoms should call 999 immediately.”
The findings were published online in the journal Heart.
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