Metabolic syndrome is the name for a group of risk factors that significantly raise the risk of developing diabetes mellitus, stroke, and heart disease. The following conditions, when occurring in multiples, are risk factors for metabolic syndrome: an increase in waistline indicative of abdominal obesity; high serum triglycerides; low HDL cholesterol level sometimes referred to as “good “ cholesterol; high blood pressure and elevated fasting blood sugar. The syndrome is estimated to be present in 34% of all Americans age 20 and over. That number increases to 50% after the age of 59.
A study published online in the March 25 The Lancet Diabetes & Endocrinology by endocrinologists from several European countries demonstrates the relationship of this syndrome to poor and inadequate sleep. The authors reviewed studies relating sleep to metabolic health from 1998 to 2013. They found a remarkable relationship between sleep duration and metabolic syndrome. The overall rate was 22% of the studied population. However, it doubled to 48% among short sleepers getting six to seven hours of sleep and increased to an astounding 83% of those getting less than six hours.
This is not the first study to link this epidemic health problem to sleep. In a study published in 2011 in The New England Journal of Medicine, it was pointed out that 70% of those with sleep apnea have metabolic syndrome. In this study, treatment of sleep apnea with CPAP (continuous positive airway pressure) resulted in a 20% reduction of the syndrome.
In another report, the Millennium Cohort Study, published last year, 47,000 military personnel were studied. In this study, troubled sleep, short sleep, and sleep apnea predicted the onset of type 2 diabetes in a large group of healthy young military personnel.
The relationship between poor and fragmented sleep and metabolic syndrome seems to be established. Certainly, genetic and environmental factors are very important. However, the role of sleep is now becoming more prominent. We think that insufficient and fragmented sleep results in stress that in turn leads to the production of hormones such as cortisol, adrenaline, and ghrelin. As a result, these hormones can cause an elevation of blood sugar, hypertension, and obesity.
The take home message from these studies is that sleep is very important in metabolic and cardiovascular health. The authors of the study point out that we as physicians need to take a more structured approach to the sleep of our patients. They encourage the routine use of sleep questionnaires that may expose underlying problems with sleep quality and duration in routine medical practice. I think that this is an excellent idea. However, until that day comes, I encourage all of you who have or are at risk for metabolic syndrome to be very mindful of your sleep.