Radio Sputnik discussed the study with Mamas Mamas, professor of cardiology at Keele University and an honorary professor of cardiology at the University of Manchester.
Sputnik: What is the correlation between our sleeping patterns and risks of cardiovascular diseases?
Mamas Mamas: We looked at the risk of future cardiac events and mortality and what we found is that longer sleep durations are particularly associated with increased risks of death and developing cardiac events such as heart attacks, stroke, heart failure etc. It seems to be a dose-response effect and what I mean by that is that for each hour over eight hours you increased risk increases.
Mamas Mamas: I think this is one of the difficulties with one of these sorts of studies. What our study shows is that there is an association; it doesn’t necessarily show that it is a cause. What we don’t know is whether prolonged sleep is a marker of underlying cardiac problems or whether prolonged sleep may directly cause these problems. I think it’s the former. I think it’s probably a marker of either risk factors or underlying cardiac disease. For example, if you are diabetic, you smoke or you have COPD, you are much more likely to sleep for longer durations and they’re exactly the sorts of risk factors that contribute to these adverse outcomes.
Sputnik: Some people feel drowsiness if they sleep eight hours or less; how do you find the perfect balance to sleep just the right amount of time and avoid health problems? From this information, if you sleep too much you are at risk, but if you sleep too less you’re at risk too; what is the right balance?
Mamas Mamas: The guidelines say it’s between seven and eight hours; I personally only sleep six hours. I think the key factor is making sure you are refreshed; I think that whatever duration you are sleeping if you wake up and you’re feeling tired and drowsy or you’re falling asleep inappropriately during the day then there’s a problem. I think then you need to seek medical attention, to be referred to a sleep laboratory that can really investigate your sleeping patterns. I think also if you’re finding that you’re sleeping for long periods of time then you need to think about your lifestyle: so think about are you at the right weight, do you smoke, are you drinking a lot of alcohol? Perhaps you need to visit your primary care provider or a GP to check your blood pressure, cholesterol and calculate what your cardiac risk is. If it’s very high you may undertake lifestyle changes or even start taking medications like Astatine.
Mamas Mamas: I think that one of the problems with this sort of analysis is that the methods by which people ascertain sleep aren’t very robust; often they’re questionnaires. And we know that if people are asked questionnaires the responses may not be entirely accurate. When you ask very overweight people that you see in clinic – “how much do you eat?” – they often say, “I hardly eat anything at all, doctor.” We also know that studies that have actually monitored people’s sleeping at sleep labs only correlate moderately well with how much patients report that they sleep. Going back to your question about when you should sleep, I don’t think there’s any really strong data around, there’s no proper sleep studies, for example, that have put people to sleep at different times and then looked at future outcomes. I think that’s a very difficult question to answer. I think the main thing is that if you feel refreshed then that’s good sleep.
Mamas Mamas: I don’t think it’s a matter of safety. For example, by origin I’m Mediterranean and in these countries you often have a siesta because the temperatures can hit 40 degrees Celsius and that’s just normal, that’s part of people’s lives. So, I don’t think there’s any adverse risk from that. I think that if you’re going to bed for a period of time, you wake up and you’re feeling tired during the day and then you’re falling asleep inappropriately – I think that is a problem and there are conditions that can show this. This may suggest that the quality of your sleep overnight isn’t good; you may have a condition called obstructive sleep apnea, which is a condition particularly of overweight people or people that drink too much. It’s a condition when for short periods of time you can stop breathing during sleep and that can then cause problems with feeling drowsy and tired during the day and that is associated with quite a high risk. It may be worth seeing your GP who can arrange a sleep study if that’s the case.