Sleep and cardiovascular health in women : the Stockholm female coronary risk study

Abstract

Background: Both sleep disturbances and snoring has been related to an increased mortality and CHD risk. However, despite the fact that women report sleep difficulties more often than men, most studies have been done in men. A large amount of the studies is of cross-sectional character and no conclusions about cause and effect can be drawn. Few studies have investigated possible underlying mechanisms as e.g. the metabolic syndrome and atherosclerotic progression. Rarely the change of sleep quality over a longer time period has been studied.

Aims: 1) To examine the effect of poor sleep quality on prognosis of CHD and wether this association can be explained by depression. 2) To examine the association between the metabolic syndrome, snoring and sleep quality, respectively, among healthy women. 3) To examine the effect of snoring on the progression of atherosclerosis. 4) To describe changes in women's sleep quality over a time period of nine years and to examine the relation of sleep at baseline to cardio-cerebro - vascular health outcome after nine years.

Material and Methods: This doctoral thesis is based on data from the Stockholm Female Coronary Risk (FemCorRisk) Study. The FemCorRisk stduy is a population-based casecontrol study which comprises 292 women aged 65 years or younger who were admitted for an acute event of CHD between 1991 and 1994 in any of the coronary care units of all hospitals in the greater Stockholm area. Age matched healthy controls from the census register were examined. All women answered an extensive questionnaire about their lifestyle and socio-economic status, including a short version of the Karolinska sleep questionnaire. 103 women were followed for three years for progression of atherosclerosis. All CHD patients were followed for 5 years for death from CHD, recurrent myocardial infarction or revasculatization procedure. Nearly all control women were followed for nine years and sleep quality; health and employment status and were recorded.

Results: In coronary patients poor sleep quality was related to a more than doubled risk of recurrent events (HR=2.5; 95% Cl: 1.2-5.2) during five years. This association could not be explained by depressive symptoms. Also waking up not well-rested was associated with an increased risk for a recurrent event. Snoring in combination with feelings of tiredness was associated with an accelerated progression of atherosclerotic luminal narrowing of the coronary vessels during three years compared to non-snoring women (0. 18 mm vs. 0. 07 min change, p<. 000 1). In healthy women snoring was significantly and poor sleep quality borderline associated with the metabolic syndrome. Snoring women had an odds of 4.5 (95% Cl: 1.7-11.9) for the metabolic syndrome compared to non-snoring women. Furthermore, poor sleep quality was related to an increased risk of cardio-cerebro-vascular disease during nine years (OR=1.2; 95% Cl: 1.0- 1.4). Women with poor general health and cardiocerebro-vasculare disease reported worse sleep quality than their healthy counterparts.

Conclusions: Both poor sleep quality and snoring were associated with CHD vulnerability in women. In healthy women the metabolic syndrome is suggested as a possible mediator of this association. Poor sleep is suggested as an early predictor of ill-health and should be taken into consideration of clinical physicians.