The Yahoo Health headline “Not enough sleep associated with weight gain” caught my eye last Wednesday. In a long-term study 68,183 middle-aged women, from Case Western Reserve University, were asked to provide information on their typical night’s sleep and then reported their weight every 2 years. The authors found that women who slept ≤ 5 hours per night were 32% more likely to gain a significant amount of weight (≥ 33 pounds) than those who slept 7 hours per night. Furthermore, these sleep-deprived women were 15% more likely to become obese in those 16 years! I decided to look at published medical studies on what lack of sleep can do to your well being.

Adolescents and sleep

Do sleep problems adversely affect the learning, cognitive and memory capabilities of adolescents? A Canadian study involving 3010 high school students examined the association of sleepiness and performance in both academic and extracurricular activities in these students (BMC Public Health 2006; 6: 116). Based on previous findings that adolescents require at least 8.5 hours of weeknight sleep, 70% of the students were found to be mildly to severely sleep-deprived. About 40 % of the students reported excessive daytime sleepiness (ESS) and this is significantly associated with poorer grades, late to school, being extremely sleepy at school, reduced participation in extracurricular activities and missing social or sport events. One quarter of the students who felt that their grades had dropped because of sleepiness reported 26-27 minutes less weeknight sleep than their peers who did not drop their grades. While this amount of time seems small, this finding concurs with the findings of another study.

Memory is crucial to learning and sleep is critical for memory. An earlier publication by Smith discussed the relationship between memory, sleep and learning. He reported that declarative material (rote memorizing) is usually consciously learned. Procedural material (learning a novel cognitive or motor task) is normally unconsciously acquired. Declarative material may not seem very sensitive to sleep loss but procedural material is very sensitive to sleep loss.

The next time you read a teacher’s report on your teenage child informing you that he has developed aggressive and delinquent behaviour in class and has social and attention problems, you might not want to immediately assume that he has mixed with the wrong company or worry that he has attention–deficit disorder. Perhaps you might consider the possibility “Is he getting enough sleep” as well?

Inadequate sleep and your health

An American epidemiologic study examined the relationship between self-reported sleep duration and the diagnosis of hypertension (high blood pressure) in 4810 subjects. These subjects were observed over a period of 8 – 10 years. The investigators found that subjects between the ages of 32 and 59 years who reported averaging ≤ 5 hours of sleep per night were 2 times more likely to develop hypertension. This association was not observed in those aged 60 years or above (Hypertension 2006; 47: 833 – 839).

Blood pressure and heart rate follow a normal cycle called a diurnal pattern. Blood pressure gradually falls at the onset of sleep and remains low until the moment of awakening when it rises quickly. Normally the blood pressure dips by an average of 10 – 20 % during sleep. By sleeping fewer hours per night, we are subjecting our body to a higher average blood pressure and heart rate for each 24-hour period. A longer waking time also lead to increased exposure to physical and psychosocial stressful events. These stressful exposures would increase blood pressure and heart rate as well. Prolonged exposure to increased total 24-hour haemodynamic (blood circulatory) load due to short sleep duration could lead to adaptation of the arteries and left heart chamber to adjust and work at an average higher blood pressure. Indeed, the diurnal pattern is preserved in hypertensives but the blood pressure is set at a higher level.

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People with hypertension are at an increased risk of having strokes, heart attacks and kidney problems. Hypertension, diabetes and obesity are interrelated and are worldwide health problems. The National Sleep Foundation surveys found that the average sleep time in United States has fallen from 9 hours in 1910 to 7.5 hours in 1975 and 6.8 hours in 2005. The percentage of adults reporting that they sleep <6 hours per night has risen from 12% in 1998 to 16% in 2005. Furthermore 26% of men and 17% of women reported that <6 hours of sleep is sufficient for them to function optimally during the day. While it may be true that you can ‘make do’ with <6 hours sleep per night, what health problems you are potentially storing up is just waiting for you round the corner. A patient of mine recently told me that she is only sleeping 3 hours per night, 365 nights per year! Burning the candle at both ends may well allow you to fit in ever more things, be it work or leisure activities, into that 24 hours; however it may eventually come back to haunt you in time to come. As the saying goes “You reap what you sow”.

A few days ago, at the end of a consultation with a Cambodian patient, the young grand-daughter of the patient asked me if she could ask a question. She wanted to know if diabetics are allowed to have sugar in their diet. Having heard my answer, she informed me that in her home in Pnom Penh she had been told that if diabetics take sugar in their diet, they will develop cancer!

Sugar is a member of the carbohydrate family. The three major macro-nutrients which supply energy to the body are fat, protein and carbohydrates. Carbohydrates take the form of sugars (mono- and di-saccharides), oligosaccharides, starches and fibres (polysaccharides). Starch and sugars are an easy source of energy or accessible fuel to the body during physical exertion. Simple sugars or mono-saccharides are present in fruits, berries, vegetables and honey. The combination of two simple sugars gives rise to di-saccharides. These occur naturally in sugar cane and fruits, for example. Milk and dairy products contain sugar as well and the main form of sugar found is lactose. Dietary fibres, a form of carbohydrate, are important for ensuring good bowel action and a diet with the right amount of carbohydrates may help in preventing body fat accumulation. Furthermore, carbohydrates also contribute to the texture, taste and appearance of the food, thus giving rise to a more varied and enjoyable diet. Life would indeed be quite miserable if we were to exclude all forms of carbohydrates!

When you consume carbohydrates, the blood glucose level rises and then falls subsequently. This rise and fall in glucose level is called the glycaemic response and is important for appetite control and especially to diabetics. The measurement of the glycaemic response of different foods with reference to the standard white bread or glucose is called the glycaemic index (GI). Examples of food with a low GI factor include noodles, lentils, apple, pears, oranges and baked beans. Banana, sweet corn, pineapple and white sugar have an intermediate GI factor and white bread, baked potato, white rice and honey have a high GI factor.

Most adult diabetics have type II diabetes. The tissues in these individuals are resistant to the action of the hormone, insulin. The body tissues have become less sensitive to the effect of the insulin molecule and thus require more insulin to be secreted by the pancreas before glucose moves from the blood stream into the cells. Obesity and physical inactivity increase the likelihood of developing type II diabetes. Weight reduction is an important part of the medical management of diabetics and is achieved through dietary control of the total number of calories consumed daily and an adherence to a regular programme of physical activities. All diabetics are encouraged to consume a wide range of carbohydrate foods. Low GI foods are slowly digested and can help in regulating the blood glucose control. Most dietary management plan for diabetics allow a modest amount of ordinary sugar in a meal.

The report by the Food and Agriculture Organisation of the United Nations on Carbohydrates in Human Nutrition had the following important messages for the public:

1. Carbohydrates provide more than energy alone. Dietary carbohydrates have many other health benefits.
2. An optimum diet contains at least 55% of energy from carbohydrates and 20-35 gm dietary fibre per day for all those above 2 years old.
3. In order to be sufficient in essential nutrients and dietary fibre, the diet must comprise of a wide range of carbohydrate-containing food stuff.

So LS, when you return to Phnom Penh, you can tell your diabetic friends or relatives that consuming sugar will not give you cancer. However, obese people do have increased risk of developing diabetes and they also have an increased risk of developing certain types of cancer!

The metabolic syndrome is diagnosed when an individual has three of the following conditions: abdominal or central obesity (waist circumference > 102 cm in men and > 88 cm in women), high triglycerides level, low high-density lipoprotein (HDL) cholesterol level, high fasting blood glucose level or high blood pressure. It is also known as Syndrome X or insulin resistance syndrome.

The consequences

Due to lifestyle changes in many developing and developed countries, lack of physical activity has led to an increase in obesity in the population. Obesity and lack of exercise are known to lead to reduced tissue response to the action of insulin. This is called insulin resistance. The presence of insulin resistance leads to a series of deleterious events taking place within the body. Insulin resistance causes an increase in the low-density lipoprotein (LDL, the ‘bad’ cholesterol) and triglyceride levels in the blood. The HDL level (the ‘good’ cholesterol) is concomitantly lowered in these individuals. This combination gives rise to the deposition of fatty plaques within the artery walls causing narrowing of the arterial lumen. With time the damage to the artery will lead to cardiovascular disease and stroke. The body’s response to insulin resistance is to increase the level of circulating insulin and because the body is less sensitive to insulin, the circulating level of glucose is similarly much higher than normal. Chronically elevated blood glucose level will lead to end organ damage such as cardiovascular disease and kidney disease. In response to the high insulin level, the kidney retains more sodium within the body thus leading to a higher blood pressure.

In a recent article from France (J Hypertens 2006; 24: 1165), the researchers studied 2738 subjects who had an elevated waist circumference or the metabolic syndrome. These individuals did not have microalbiminuria (leakage of albumin from the kidney) or diabetes at the start. After 6 years, 9.3% of the individuals developed microalbuminuria, a sign of underlying kidney damage. A waist circumference of > 94 cm in men and > 88 cm in women were predictive of the development of microalbuminuria.

The problem

In Europe the metabolic syndrome is seen as a major health problem and will impact heavily on the future health and social welfare costs within the European Union (EU). One in six Europeans has the metabolic syndrome. In some European countries one third of the population has the syndrome. Even in countries such as Greece or France, where the traditional healthy diets and lifestyle had afforded them protection, the metabolic syndrome is rearing its ugly head. The EU has set up the LIPGENE project specifically to tackle the issue of the metabolic syndrome.

What can you do?

Keep a healthy weight
If you are overweight, try to lose 5 – 10% of your body weight. This will help.

Eat the right food
Whole grain food, food rich in long-chain omega-3 fatty acids (ie fish) and the Mediterranean diet will help to reduce the risk of the metabolic syndrome.

Move those joints
You should aim for at least 30 minutes of physical activity per day. Next time you are waiting for the lift to arrive, stop! Take the stairs instead. When you next go down to the local shops, walk instead. If you are on the bus, get off one stop early and walk the rest of the way. Instead of reaching for the TV remote control, get up and walk to the set. You will be surprised how these ‘insignificant’ movements add up to a healthier body.