Do you often struggle because you do not sleep enough at night? Or maybe you sleep as much as you can every day, since the programs allow it? None of these two options is good, suggests a new study, and you may be at risk for metabolic problems. We already know that too little sleep can have an impact on our health in many ways; but, on the contrary, to what extent does too much sleep affect our well-being? A study recently conducted by researchers at the Seoul National University College of Medicine in South Korea found that both of these extremes are likely to increase the risk of metabolic syndrome. This refers to a group of associated metabolic conditions, including low glucose tolerance, hypertension and obesity. Dr. Claire E. Kim and her team analyzed data from the Health Examinees (HEXA) study, a large population study that studies the interaction of genetic and environmental factors in the context of chronic disease incidence in Korea of the South. Their results – reported in the journal BMC Public Health – not only indicate a correlation between sleep extremes and the metabolic syndrome, but also suggest that risks may be different depending on a person’s sex.
Kim and the team analyzed the medical data of 133,608 men and women between the ages of 40 and 69. The participants also declared for themselves how much they sleep every day, including nighttime sleep and any daytime nap. The HEXA study included information on the participants’ clinical histories, the use of drugs, the modification of lifestyle factors and the family’s medical history. All volunteers also provided samples of plasma, serum, blood cells, urine and chromosomal DNA, among other things. Analyzes of data collected by participants – including self-reported sleep hygiene information – revealed that less than 6 and more than 10 hours of daily sleep were related to the presence of metabolic syndrome. Individuals were thought to have a metabolic syndrome if they had at least three of these telltale symptoms: excess fat around their waist; high levels of triglycerides; low levels of HDL cholesterol; fasting high blood sugar; and hypertension. Just over 29% of male participants had metabolic syndrome and 24.5% of women showed signs of this condition. The team noted some differences in risk models.
Thus, women who slept little – for less than 6 hours a day – were more prone to having a higher waist circumference, indicative of excess belly fat, than women who slept for 6-7 hours a day. Men who slept for less than 6 hours were more likely to have not only a higher waist circumference, but also a metabolic syndrome. Regarding excessive sleep – defined as more than 10 hours of sleep each day – it was linked to elevated triglyceride levels, as well as to metabolic syndrome, in men. But in women, it was linked to even more negative health outcomes: not only the metabolic syndrome and high levels of triglycerides, but also high blood sugar, low HDL cholesterol and higher waist circumference. Among the participants, about 13% of the women and 11% of the men slept too little, and 1.7% of the women and 1.5% of the men slept for more than 10 hours a day. It is not clear how sleep patterns can influence the development of the metabolic syndrome, but researchers note that sleep duration could affect the production of key hormones that regulate appetite and how much energy produces and consumes our body. Kim and colleagues also note that the research has observed an association that may not necessarily speak of a cause and effect relationship.
The authors recognize the fact that sleep time information was self-reported, so there was no objective measurement in this regard, as did the analysis that amalgamated nocturnal sleep and daytime naps. The size of the people involved, however, makes the study more than significant; and reinforces the idea that a bad quality of sleep, by default and even by excess, can condition our health in a serious way.
- edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.
Kim CE et al. BMC Public Health. 2018 Jun 13; 18(1):720.
Kim CE et al. Int J Environ Res Public Health. 2017;14(11).