Amyotrophic lateral sclerosis (ALS) or motor neuron disease results in the death of brain neurons. Patients lose deep sleep and REM sleep as the disease progresses and excessive daytime sleepiness is common. The physical decline of the torso muscles means some patients find they sleep better with a CPAP machine.
Although scientists don’t know the detailed biochemistry of ALS, one theory revolves around the low levels of serotonin and high levels of glutamate in the brains of patients and which may contribute to cell death. The circadian hormone melatonin is made from serotonin, so that may also be a reason for poor sleep in ALS patients.
Huntington’s disease results in widespread death of neurons in the brain. Experiments in mice show the suprachiasmatic nucleus keeps functioning normally, so the decline in sleep quality in Huntington’s patients probably due to circadian abnormalities. The circadian functions of other parts of the body outside the brain are affected in patients, too. People with Huntington’s have less REM sleep, more sleep fragmented sleep, and delayed sleep phase (http://www.ncbi.nlm.nih.gov/pubmed/20236854)
Lewy Body disease is a common form of dementia that affects 1.3 million people in the United States. The symptoms include excessive daytime sleepiness and napping of two hours during the day. http://www.aafp.org/afp/2006/0401/p1223.html There is no cure and treatment is directed at mitigating the effects of symptoms. REM Sleep Behavior Disorder is relatively common in patients, and indeed instances of this disorder are often a sign that some form of dementia will develop. More than half of RBD patients do so.
I love sleep. My life has a tendency to fall aprt when I'mm awake, you know?" - Ernest Hemingway
The brains of people with Lewy Body Dementia seem to have lower than normal levels of the neurotransmitters acetylcholine and dopamine in key areas.
Alzheimer's. Researchers found seniors with sleeping problems tend to have higher levels of beta-amyloid plaques characteristic of Alzheimer's DIsease. Whether the plaques cause sleep problems or the two have a common cause is not clear. The brain's glymphatic system removes waste products that may contribute to neurodegenerative diseases, and lack of good sleep may interfere with that system's functioning.
People with brain tumors – both malignant and benign – tend to sleep more than healthy people.