Alzheimer’s: Backup internal clock may offer protection, study says

During the aging process, changes in circadian rhythms may be associated with Alzheimer’s, Parkinson’s, ALS and other neurological and psychiatric conditions. In some older people, however, a backup internal clock may provide protection from these diseases.

An Internal Clock

An influential set of genes keeps human bodies on a schedule. These genes monitor circadian rhythms, which help you wake up in the morning, grow sleepy in the evening and repeat the cycle the very next day. These genes control a number of systems in the body, including sleep and metabolism.

As people age, however, these circadian rhythms have a tendency to shift. For example, older adults often rise earlier in the day than they did in their younger years and eat dinner at an earlier hour.

Gene Research

This shift is a normal part of the aging process, but researcher Colleen McClung of the University of Pittsburgh Medical Center wanted to know more about these changes and how they affect the body. In a study published in Proceedings of the National Academy of Science, McClung and her associates studied brain tissue samples from 150 recently deceased people. The samples came from people with a range of ages at the time of their deaths. As they expected, the scientists found that in the older adults, the genes that controlled their circadian rhythms in their younger years had a “breakdown” of sorts as they aged. They no longer functioned with the same rhythmicity that they once did.

While that part of the findings was expected, their research also uncovered something quite surprising. In some of the older adults, there was a second set of genes at work. It seemed that this set also kept the body’s systems in a rhythm, but these genes were at work only in the brains of older adults. This set of genes was not activated in the tissue samples from younger bodies. The researchers described the second set of genes as a possible “backup” internal clock that can grow stronger with age.

A Possible Disease Connection

Scientists know that in both plants and animals, including humans, a breakdown of proper daily rhythms can lead to problems throughout the organism. Additionally, many neurological and psychiatric diseases found in aging adults are associated with disrupted circadian rhythms. In Alzheimer’s patients, for example, “sundowning,” in which restlessness and irritability manifest in the evenings, is a common cause for concern.

One theory for these clock-related symptoms is that when circadian rhythms are thrown off, neurons are activated when they should be at rest and resting when they should be active. This skewed schedule harms the neurons’ metabolisms and causes them to degenerate. The researchers on this study postulated that perhaps the compensatory internal clock that they discovered might offer protection for some individuals from this breakdown and their associated late-in-life neurodegenerative diseases. Through further study, McClung and her team plan to research the presence — or lack thereof — of these backup genes in Alzheimer’s patients.