Insomnia, a symptom and a disease risk

There’s a genetic link between insomnia and psychiatric disorders and metabolic diseases such as type 2 diabetes, according to a new study. Expanding on previous twin and genome-wide association research showing sleep disorders may be inherited, US researchers have identified specific genes that cause sleep problems and concluded that depression is “partially heritable”. The study was published in the journal Molecular Psychiatry this week.

Sleeplessness is often a symptom caused by several unrelated and diverse conditions, ranging from psychological triggers like anxiety and depression, to physical ailments like asthma, Parkinson’s and chronic pain. This makes it imperative for people with insomnia to be screened for the underlying medical cause so it can be treated.

If the cause for disrupted sleep is simply poor sleep hygiene, not using bright lighting in the bedroom, choosing a quiet room to sleep in, and shunning back-lit screens -- such as smartphones, ipads, TVs and laptops -- at bedtime can improve sleep.

The lack of sleep initially causes irritability, impairs working memory, lowers attention and causes poor motor function. Chronic deprivation not only aggravates the existing condition that is causing the sleeplessness, but also causes new health problems, such as weight gain, high blood pressure, insulin resistance, systemic inflammation, visceral fat deposition, and dyslipidemia (high blood facts such as bad LDL cholesterol and trigycerides).

Among the common problems causing chronic sleep loss are:

Weight gain
Sleeplessness lowers growth hormone secretion that is linked to weight gain, according to the US National Sleep Foundation. Studies have shown a link between short sleep duration and increased body weight, suggesting that sleep duration may be an important regulator of body weight and metabolic and endocrine function.

Sleep deprivation affects the hormones that regulate appetite and metabolism. A study at the University of Chicago some years ago found that people who slept four hours a night for two nights had an 18 percent decrease in levels of appetite-suppressing hormone leptin, and a 28 percent increase in the hormone ghrelin, which stimulates appetite. This fall and rise led to a 24 percent increase in appetite, along with higher cravings for sweets, salty foods, and starchy foods, such as breads and pasta, found the study.

Diabetes
Sleep deprivation causes βeta-cell dysfunction and increased inflammation and oxidative stress, which leads to worsening glycaemic control in people with diabetes, according to the International Textbook of Diabetes Mellitus, 4th edition.

It works both ways. People with diabetes have poor sleep quality measured as trouble falling asleep and sleeping for a shorter duration, especially if theu have poorly controlled sugar levels, according to a study published in January in the journal PLOS One . The study found that obstructive sleep apnea, a major cause of disrupted sleep, also leads to poorer glycaemic control (both HbA1c and fasting plasma glucose) and glycaemic variability in people with diabetes after adjustments for several confounders, such as age, sex, race, weight, number of diabetes medications, level of exercise, years of diabetes and total sleep time.

Heart Disease
With mounting evidence linking insomnia to hypertension, heart attacks and death, some experts have argued that sleep disturbances be included as the tenth potentially modifiable cardiovascular risk factor, according to the American College of Cardiology.

Sleeplessness was linked with higher risk of developing heart disease over 10 years among 86,329 postmenopausal women, revealed the US National Institutes of Health Women’s Health Initiative. Another study of 44,080 men and women diagnosed with insomnia in Taiwan had higher incidence of stroke and heart attacks compared to controls a decade later.

Blood pressure usually falls during the sleep cycle and interrupted sleep adversely affects this normal decline, leading to hypertension and heart disease. Sleeping for less than six hours is a risk for high blood pressure.

Chronic sleeplessness leads to a systemic inflammatory state, measured by a rise in inflammation markers, such as cytokines, C-reactive proteins and Interleukin-6, both of which raise risk of heart disease.

Depression
Disturbed sleep is a key symptom of depression, with roughly three in four people with diagnosed depression having insomnia, according to a study published in the journal Dialogues in Clinical Neuroscience. Over time, it worsens symptoms of depression, aggravating feelings of low energy, social withdrawal and isolation, feelings of sadness or hopelessness.

Like all other disorders, nipping the problem in the bud can prevent acute episodes – say, triggered by anxiety or emotional distress—into turning chronic. People with insomnia are fatigued and less to exercise and more likely to choose unhealthy foods, which feeds the cycle of depression.