Aging and Alzheimers
By 2050, an estimated 16 million Americans will be in the throes of dementia. The majority of these individuals will suffer from Alzheimer’s disease.
Unable to function on a day-to-day basis, they will forget telephone numbers, home addresses, who their children are, even their own name. And, they will most likely suffer from Sleep Disordered Breathing.
As with any other muscle in the body, the airway loses its patency, or muscle tone, as it ages. The soft tissues at the back of the throat become less elastic and collapse in on each other when the body relaxes during sleep. In the elderly, (over 60), the most common cause of Sleep Disordered Breathing is loss of airway patency.
Although the non-demented elderly are at risk for developing SDB, with the National Institutes of Health estimating one in four individuals over 60 has undiagnosed Sleep Disordered Breathing, those with Alzheimer’s are at an even greater risk.
The journal Aging found that in those suffering from Alzheimer’s disease, “SDB occurs more frequently than in non-demented older subjects, and its severity is correlated to the degree of cognitive impairment.”
Scientists in Advances in Cell Aging and Gerontology assert that Sleep Disordered Breathing occurring in the context of Alzheimer’s can be treated as “reversible dementia.” Correcting the airway pathology that causes a Sleep Disordered Breathing problem “improves cognitive dysfunction.”
The collaboration of researchers from various medical and behavioral specialties is slowly uncovering a connection between Alzheimer’s disease and Cardiovascular Disease and Sleep Disordered Breathing.
This strange link is a gene called Apolipoprotein E. Apolipoprotein is an otherwise harmless and useful protein. Like all genes, it varies within the population in the form of alleles. In the case of Apolipoprotein, there are three genetically inherited alleles, e2 e3 and e4. Everyone carries two copies of Apolipoprotein, one allele copy inherited from each parent.
The apoE2 allele is believed to protect against Alzheimer’s disease. However, the apoE4 allele has been associated simultaneously with Alzheimer’s disease and Cardiovascular Disease. Sleep Disordered Breathing has been discovered in statistically significant Alzheimer’s and Cardiovascular Disease populations of patients carrying the apoE4 allele
Researchers at the Center for Narcolepsy at Stanford’s Center for Human Sleep Research estimate that 50 percent of sleep apnea cases could be the result of genetic factors, and 8 percent “may be directly related to the inheritance of at least one copy of ApoE4.”
People carrying the apoE4 allele may be twice as likely to suffer from Sleep Disordered Breathing than those that don’t, according to Stanford.
Scientists at the center speculate that “sleep apnea may actually be the symptom of a very early form of brain injury. The plaques in the brain associated with Alzheimer’s disease may affect how a person breathes during sleep.” But much research is still to be done.