The causes of secondary or concomitant chronic insomnia can be categorized as altered periodic rhythms, behavioral disorders, environmental factors, other sleep disorders, allergic sleep, menstruation and pregnancy, substance use and abuse, but most commonly insomnia co-morbid with medical, neurological, and psychiatric disorders. Altered periodic rhythms Patients with altered synchrony between endogenous periodic rhythms and the environment can result in four forms of insomnia, namely delayed sleep phase syndrome, early sleep phase syndrome, irregular sleep-wake pattern, and non-24-hour sleep-wake syndrome. This group of cases accounts for 2% or less of chronic sleepers. Delayed sleep phase syndrome Patients present with late nighttime sleep and late morning wakefulness with excessive sleep that interferes with daytime functioning. Without social or work restrictions, patients usually fall asleep between 2 and 6 a.m. and wake up between 10 a.m. and 1 p.m. Diagnosis relies on a detailed history and physical examination. It must be distinguished from changes in sleep-wake patterns that occur as a result of lifestyle changes. Sleep phase advance syndrome Nocturnal sleep occurs at a time that drifts to earlier than the desired sleep time. Habitual early sleep onset with early morning awakening (1:00am-3:00am). Must be distinguished from early morning awakenings due to depression. Irregular sleep-wake pattern Irregular sleep-wake pattern due to lack of underlying periodic rhythm. Patients do not have major nighttime sleep periods, but rather 3 or more short sleeps during a 24-hour period. Total sleep time is normal during the 24-hour period. Nocturnal insomnia or daytime sleep may be seen. Non-24-hour sleep-wake syndrome The pattern of sleep-wake in these patients is not clearly related to environmental time cues and seems to depend only on intrinsic biological rhythms, which are slightly longer than 24 hours. The process is chronic and persistent. Sleep onset and wakefulness are delayed day by day and are characterized by alternating insomnia and excessive sleep cycles. Behavioral disorders A variety of behavioral disorders may lead to insomnia and failure to regain energetic sleep. These behavioral disorders include poor sleep hygiene, sleep onset association disorder, and nocturnal meal (drinking) syndrome. Poor sleep hygiene can begin at any age. Insomnia stems from a lifestyle that increases wakefulness or decreases sleep, such as excessive consumption of stimulants (coffee, tea, cola), intoxication, smoking, stressful exercise, excitement, and mentally stimulating activities too late without sleep. Patients may spend too much time in bed, engage in non-sleep related activities in bed, such as doing housework, watching TV, talking on the phone. Sleep and wake times vary erratically from day to day, accompanied by frequent daytime napping. Poor sleep hygiene may interact with other factors (e.g., acute stress or mood disorders) involved in insomnia, which may not be sufficient on their own to induce sleep disturbances. Sleep onset association disorder The inability to fall asleep in the absence of certain desired environments or objects. Typically seen in children who cannot fall asleep unless they have a bottle, dummy nipple, or favorite toy. Usually resolves by 3-4 years of age, but can persist into adulthood, e.g., dependent on watching TV or listening to the radio to fall asleep. Nocturnal feeding (drinking) syndrome Characterized by repeated awakenings. In many cases, awakenings do not seem to be prompted by true hunger or thirst, but only after eating (drinking) can they fall back asleep. It accounts for 5% of children aged 6 months to 3 years. Environmental factors Four conditions are involved: environmental sleep disorders, food allergy insomnia, toxin-induced sleep disorders, and plateau insomnia. Environmental sleep disorders The harsh environments that interfere with sleep include noise, odors, bright light, extreme room temperatures, and bed partner snoring. The elderly are more likely to suffer from this type of insomnia. Sleep returns to normal after the cause is removed. Food allergy insomnia Some foods or beverages can cause increased wakefulness and can occur in both children and adults, most often in children from infancy to 4 years of age. Other allergic symptoms such as rash, gastrointestinal discomfort, and labored breathing may be present. Sleep returns to normal after the allergen is eliminated. Altitude insomnia Insomnia can occur at altitudes above 2000-4000 meters and can be accompanied by easy fatigue, headache, and loss of appetite. The higher the altitude, the more severe the symptoms. Acetazolamide (which produces substitution acid) can promote insomnia quality. Oxygen therapy does not promote sleep quality. Valium (inhibits breathing) should be avoided. Other sleep disorders include sleep apnea syndrome (see separate article), restless legs syndrome, and periodic limb movement disorder. Restless legs syndrome is more common in women. It involves discomfort in the lower extremities and is apparent when sitting, lying down, or remaining upright. This “creeping” or “crawling” sensation is worse at night; it extends from the soles of the feet and ankles to the lower legs and occasionally to the thighs. Movement of the calves may partially or completely relieve the symptoms, but they reappear when the calf movement stops. The incidence increases with pregnancy, anemia, uremia, and wind-like disease. It causes insomnia because the discomfort often occurs before sleep. Heteromorphic sleep This is a group of somatic phenomena that arise during sleep and break into sleep, manifesting as skeletal muscle or autonomic activity during sleep, and if severe enough, leading to chronic insomnia. 1. Blurred consciousness awakenings Patients awaken during deep sleep and have episodes of blurred consciousness, usually in the first half of the night. Symptoms include disorientation, inappropriate behavior, and no memory of the episode. If it occurs frequently, it can lead to sleep breakdown. 2. Sleep terrors Patients awaken suddenly during deep sleep, rise abruptly from bed and scream, usually in the first half of the night. There is intense fear, blurred consciousness, tachycardia, shortness of breath, profuse sweating, sleep talking or screaming, incontinence, and no memory of the attack. 3. Sleep walking disorder Commonly in the first half of the night, occurring during deep sleep. Patients have decreased arousal ability, irrational behavior, and no memory of the episodes. 4.Nightmares Patients are suddenly awakened by nightmares and are very fearful and anxious, and can vividly recall the dreams. Often, they cannot fall back to sleep quickly. 5.Nocturnal paradoxical dystonia Stereotypic dystonic movements (throwing-like or tachycardia-like), followed by awakening from sleep. 6. Painful spasms of the lower limbs at night Painful spasms of the peroneal or foot muscles do not cause awakening from sleep, and pain can be relieved by forceful dorsiflexion of the foot or local massage. Only after the pain disappears can you go back to sleep. 7. Sleep-related painful erection Painful penile erection is produced during sleep, but there is no obvious penile obstruction or pain during sexual intercourse upon awakening. It can lead to recurrent awakenings and insomnia. Pregnancy and menstruation During the menstrual cycle, sleep fragmentation and insomnia can occur. The quality and duration of sleep varies markedly during different periods of pregnancy. From the second trimester onwards, sleep decreases and nocturnal awakenings increase, reaching a peak in the last trimester. Most patients return to normal sleep within a short period of time after delivery. Medications and substances This is particularly important in the elderly. Normal use, overdose, dependence, withdrawal and adverse reactions to medications can all contribute to insomnia, but it is difficult to determine what effects the combination of different medications may have on sleep. Drugs/substances that can cause insomnia include: alcohol, appetite suppressant diet pills, anti-stimulants (lamotrigine, phenytoin), antidepressants (fluoxetine, venlafaxine), antihypertensive drugs (b-blockers, calcium channel blockers, colistin, methyldopa, reserpine), antineoplastic drugs (erythromycin, goserelin, a-interferon, leuprolide acetate), anti-Parkinson’s disease drugs, bronchodilators ( salbutamol, m-hydroxyisoprenaline, salmeterol, m-hydroxyisoprenaline), oral contraceptives, corticosteroids, cough and cold medicines (ephedrine, pseudoephedrine), diuretics (thiazides), hormones (progesterone, thyroid hormones), lipid-lowering drugs, nicotine, euphoric substances (coffee, cocaine, dextroamphetamine, lidilim, modafinil, pemoline), theophylline. Special medicine note that the elderly use antihypertensive drugs extensively, and they must check antihypertensive drugs when they have insomnia.