Recent studies have suggested that those who have inadequate amounts of sleep see a reduction in the functioning of their immune systems. These individuals often times have an increased susceptibility to the common cold and a reduction in sleep may render vaccinations less effective. A decrease in the number of some types of immune cells have been seen in those with prolonged insufficient sleep.
It has also been established that bacterial infections affect your sense of sleepiness and the amount of time spent in each stage of sleep. An increase in sleepiness is an early and enduring symptom of infections involving the whole body, suggesting that sleep is playing a critical role in the body's fight against the foreign invaders.
Infections due to other causes (i.e. viruses) have a similar effect on our sleep.
Increases in the steroid hormone cortisol have been attributed to this decrease in immune function.
Type II diabetes results in difficulty of the body to regulate its blood sugar levels. Studies have found that it can take 40% longer to regulate blood sugar following a high carbohydrate meal in those that are sleep deprived. A 30% decrease the release and ability to respond to insulin (the hormone responsible for moving glucose [sugar] out of the bloodstream) has also been found in these same sleep deprived individuals. These are all characteristics of early diabetes.
These changes in blood sugar regulation are largely due to increased levels of cortisol.
Obesity is a complex metabolic process that is often mistakenly assumed to be a simple discrepancy between one's calorie consumption and the calories they expend throughout the day. Hunger is largely governed by two major hormones; leptin and ghrelin. Leptin inhibits/suppresses hunger and when this hormone is lacking, people often feel hungry even though they have adequate energy stores. Ghrelin on the other hand increases/stimulates hunger. In sleep deprived study participants, it has been found that levels of leptin are decreased while ghrelin levels are increased.
This change in leptin/ghrelin ratio in addition to changes in our body's ability to regulate blood sugar levels suggests that poor sleep hygiene may in fact alter our eating habits potentially leading to weight gain.
Increased and prolonged levels of cortisol have been shown to have a deleterious effect on bone health. Cortisol inhibits the ongoing replacement of calcium in bone due to reducing the absorption of this mineral in the gut.
You will notice that a common hormone seems to be at the root of many of these health risks. The take away message is not that this hormone is bad. It serves some important functions when it is present in the body at regular times and within normal ranges. The increase of this hormone is, at least in part, the body's response to an underlying issue - poor sleep hygiene.
Also, association does not equal causation. Just because A and B occur together or in close proximity, it does not mean that A caused B or vice versa. In other words, it cannot be assumed that poor sleep hygiene is solely responsible for the development of these health risks. It is possible that there are other factors at play (possibly from the other two tenets of my three-legged stool analogy) that may be contributing poor health and disease.
This is not an all-inclusive list of health risks associated with poor sleep hygiene. I selected a few examples to make a case for why sleep is so important. If you're interested in learning more about sleep science, I recommend you consult one of the many texts out there on the subject. There is truly an epic amount of research on this fundamental process!
Lastly, I realize that some of you reading this article may be struggling with your own sleep hygiene issues. My intent in writing this post was to inform you of the potential implications of poor sleep habits/practices. If you're not made aware of the information, the likelihood of addressing these issues with your healthcare provider greatly decreases! If your sleep is less than adequate, please consult someone in your healthcare team.