Irregular sleep-wake rhythm disorder: causes, diagnosis and how it is managed

Most people sleep in one main block at night and are awake in the day, following a body clock (circadian rhythm) that runs to roughly 24 hours. The AASM explains that people with ISWRD show no clear circadian rhythm. Sleep comes in a series of naps across the 24 hours, in a pattern not unlike an infant who sleeps for a few hours and then is awake for a few hours.

The AASM adds that during the day it may seem as if the person is sleepy because they nap so much, and during the night it may seem like insomnia because they are awake for long periods; there is no one main sleep time. Importantly, the total of all sleep periods may or may not be normal for the person's age. MedlinePlus similarly says that the total sleep time is normal but the body clock loses its normal circadian cycle, which shows that sources vary on this point.

The Sleep Foundation distinguishes ISWRD from non-24-hour sleep-wake disorder, in which sleep times drift steadily later each day, and from delayed or advanced sleep phase, in which the whole sleep block is shifted but still regular. In ISWRD the problem is the absence of any consolidated block.

The Sleep Foundation lists the main features, and the AASM and MedlinePlus agree on the core picture of fragmented sleep with daytime napping.

• Sleeping off and on in a series of naps during the day and night.

• No regular pattern of when you sleep and when you are awake.

• Difficulty sleeping well at night, with several night-time awakenings.

• Excessive daytime sleepiness when awake.

• Naps that, according to the Sleep Foundation, typically last two to four hours.

The AASM says it is believed that some people have a weak body clock, which may happen in neurological conditions such as dementia, brain damage and mental health disorders, but also in people without a neurological problem. It says that daily light and other activities are important in resetting the sleep clock, and that poor sleep habits and too little daily light exposure may allow the disorder to occur in people who have weaker clocks.

The Sleep Foundation reports that limited findings exist on the biological mechanisms, that it likely has multiple causes, and lists as risk factors a lack of physical or social activity, too little light during the day or too much at night, and conditions including dementia, Parkinson's disease, Huntington's disease, autism, childhood developmental disorders, traumatic brain injury, chronic fatigue syndrome and brain tumour. It notes the disorder is associated with age-related diseases but can occur at any age. MedlinePlus says it usually occurs in people with a brain function problem who also do not have a regular daytime routine.

MedlinePlus advises seeing your provider if this type of irregular pattern occurs regularly and without cause. The Sleep Foundation advises speaking to a doctor if you are not getting the recommended amount of sleep or have impaired daytime functioning, and warns that sleep loss can increase the risk of accidents and health problems. The NHS says on insomnia that you should see a GP if changing your sleeping habits has not helped, if you have had trouble sleeping for months, or if it is affecting your daily life in a way that makes it hard to cope.

Getting sleep checked matters for family carers too: night-time waking in someone with dementia is a safety concern, and a new change in sleep pattern or sudden confusion can be a sign of infection or another acute illness. For sudden confusion or collapse, call NHS 111 or 999 as appropriate; that is general safety advice, not specific to ISWRD.

The AASM says the diagnosis of ISWRD is made clinically and with the use of the sleep diary, in which you record natural sleep and wake times over several weeks, and that you may be asked to track sleep with actigraphy, a wrist-worn device that records active and inactive periods over one to two weeks. It adds that the doctor should ask about medical, neurological and sleep symptoms, medications, alcohol use and family history, and do a medical and neurological examination.

The Sleep Foundation adds that when ISWRD is suspected a provider may also order blood tests or imaging, or screen for conditions such as dementia, because the disorder is associated with neurological illness. The AASM warns that trying to correct the rhythm on your own with behaviours or medicines might make it worse, especially if taking pills or alcohol.

MedlinePlus says the goal of treatment is to help the person return to a normal sleep-wake cycle, which may involve setting up a regular daytime schedule of activities and mealtimes, not staying in bed during the day, using bright light therapy in the morning and melatonin at bedtime, and making sure the room is dark and quiet at night. It adds that in older people, especially those with dementia, sedatives such as melatonin are not advised.

The Sleep Foundation adds practical points: keep a consistent sleep schedule, restrict time in bed if you cannot sleep after about 20 minutes, increase daytime light and limit evening screens, limit alcohol and caffeine, avoid daytime napping and keep the bedroom dark, quiet and cool. The NHS insomnia page gives similar sleep-habit advice, including going to bed only when sleepy, waking at the same time each day, avoiding large late meals and screens before bed and not napping in the day.

Any medicine, including melatonin and over-the-counter sleep aids, should be discussed with a doctor or pharmacist first; the NHS says sleeping aids from a pharmacy may help for 1 to 2 weeks and should not be taken for longer.

MedlinePlus says the outcome is often good with treatment, but that some people continue to have the disorder even with treatment. Where ISWRD is linked to a progressive brain condition, the underlying condition affects how much can be achieved.

In the NHS, a GP is the first step, with referral to a sleep clinic, neurology, old-age psychiatry or care-of-the-elderly services depending on the context. Private sleep clinics offer assessment and actigraphy, but a structured daytime routine and light exposure, which carers can provide at home, are the foundation of management.