Over the past decade, the vital importance of good sleep for health has been emphasised by many people in the medical profession. A recent study has suggested that 7–8 hours of high quality sleep every night is as good for your body as not smoking. Although this timeframe is said to be the “sweet spot” for good quality sleep, many people will sleep for this time and still feel unrefreshed when they wake.
But, it is actually the quality of deep sleep that determines how rejuvenated and refreshed you are the next day. There are many factors that contribute to good quality sleep which include following your genetic sleep pattern i.e. 70% people are larks — they go to bed early and wake up early, whilst the remaining 30% are night owls i.e. they go to bed late and wake up late. It is also important to go to bed at approximately the same time and wake up at approximately the same time every day regardless of whether you’re working or it is the weekend. Sleeping in a cool dark room, devoid of electronics also improves the quality of sleep.
A recent study of pooled data of 3 million people showed that sleeping outside the 7–8 hour per night window increases the risk of death and cardiovascular disease. This was a UK study published in the Journal of the American Heart Association which showed a J-shaped relationship between hours of sleep. Sleeping less than 6 hours per night has been linked to a much greater incidence of cardiovascular disease, cancer, obesity and diabetes. Poor quality sleep is linked to a 44% increased risk for coronary heart disease. Poor quality sleep is defined as non-restorative sleep or waking unrefreshed. It is suggested that the ideal sleeping time for people between 25–65 is somewhere between 7–9 hours and for those above 65 some in the 7–8 hour range.
For people who slept for 9 hours or beyond, there was a 14% increased death risk and for those who slept for 10 hours and beyond a 30% increased death risk.
There is a clear link between insufficient sleep (less than 6 hours) and hormonal changes which are associated with poor energy and increased appetite leading to obesity and impaired blood sugar levels. Insufficient sleep is also linked to inflammation which is a key factor in the generation of cardiovascular disease and cancer.
The big question is why is there a link between increased sleep time and disease? It may actually be that increased sleep is a marker of other health problems such as sleep apnoea or an underlying disease state e.g. inflammation, anaemia etcetera. In other words, it is the disease leading to increased sleep rather than the increased sleep time leading to disease. There is a known link to increasing sleeping times and depression, unemployment and lower socio-economic status — all features of increased risk for disease.
As with most situations, it is having balance in your life that is important. Too much or too little of most things can cause problems. There is an interesting similar relationship with alcohol consumption. It is suggested that teetotallers have more disease than people who are light to moderate drinkers as opposed to heavy drinkers who always come unstuck with some health issue.
The most important message here is that high quality sleep is vital but make sure it is the right dose.