For a long time now I’ve been a fan of sleep. Not just because of its relatively immediate impact on energy levels and sense of wellbeing, but also because of the research which links adequate sleep with improved health in the long term. Short sleep times have, for instance, been linked with an increased risk of heart disease. One such study as published this week in the Archives of Internal Medicine. The population being studied comprised more than 1200 Japanese men and women with an average age of 70. The group was followed for an average of just over 4 years.
All the members of this group were suffers of hypertension (high blood pressure). The individuals were assessed to see how their blood pressure at night compared with levels during the day. Generally, blood pressure falls at night. However, in some of the group blood pressure rose slightly (referred to in the study as a ‘riser pattern’).
Overall, individuals sleeping for less than 7.5 hours a night, compared to those sleeping longer, were found to be at a 68 per cent increased risk of cardiovascular disease (heart attack and stroke), death from cardiovascular disease, or what is known as sudden cardiac death. The greatest risk appeared to be for those who in addition to sleeping less than 7.5 hours, also exhibited the ‘riser pattern’ in terms of their blood pressure. Compared to those without this pattern who also slept for long, this subgroup were about four and half times more likely to suffer from one of the endpoints monitored in the study.
It is not possible from epidemiological studies to know if lower sleep times increases risk of cardiovascular disease and death, or these things are just associated with each other. However, there is at least some reason to think there is a causal link. Lack of sleep has been noted to increase activity in part of the nervous system known as the sympathetic nervous system. In turn, this can increase blood pressure. Suboptimal sleep has also been shown to induce changes which predispose towards insulin resistance (a precursor of type 2 diabetes and a risk factor for cardiovascular disease). And finally, lack of sleep has also been shown to cause a rise in the level of the inflammatory marker C reactive protein that is also associated with an increased risk of cardiovascular disease.
What this mean is that is at least some evidence which explains how a lack of sleep might increase the risk of cardiovascular disease. And all-in-all, there is good reason to believe not scrimping of sleep may add years to our life as well as life to our years.
Eguchi K, et al. Short Sleep Duration as an Independent Predictor of Cardiovascular Events in Japanese Patients With Hypertension. Arch Intern Med. 2008;168(20):2225-2231