Stress and the heart: The sleep factor

Sinus arrhythmia, sinus pauses and A‐V blocks may occur during REM sleep, during which an increase in the variability of blood pressure and heart rate occurs. Peak mortality for myocardial infarction (MI) occurs between 4.00 and 7.00 am and there is a circadian variation in myocardial ischaemia. The incidence of MI is higher in those sleeping more than nine hours as compared to those sleeping 7‐8 hours, while those sleeping less than six hours have more symptomatic coronary heart disease (CHD). Poor sleep quality also increases the risk of CHD and seems to be an indicator of mental and somatic disease. Other major factors are obesity and snoring, since habitual snoring increases the risk of hypertension and CHD. During obstructive sleep apnoea syndrome (OSAS) the pulmonary and systemic arterial pressures rise, straining the heart, and hypoxaemia increases vulnerability to fatal arrhythmias. Chronic obstructive pulmonary disease is another risk factor and part of the association between CHD and sleep disturbances could be explained even by modifications in lipoprotein catabolism.