Blind people often find it hard to align their sleep-wake cycle with 24-hour day

Melanie Brunson, who has been blind since birth, suddenly awoke and found herself standing at 15th and K streets in Northwest Washington.

She had stopped at the corner on her way home from work to await a safe time to cross and had dozed off. Even on awakening, she was so groggy she couldn’t focus well enough to hear passing cars and judge when it was safe to cross. The incident was a startling reminder of the sleep problems that had plagued her since birth.

Loading...

Comments

• Weigh In
• Corrections?

Personal Post

More health news

Magnet therapy can ease depression

Julie Appleby

Magnetic stimulation can cost $12,000 per patient. It’s unclear how effective it is for depression.

Doctors often ignore wellness steps

Consumer Reports: Patients should insist that their doctor makes time for wellness measures.

Shift work may strain the heart

Linda Searing

Shift work may strain the heart, but study finds no additional risk of mortality.

“Who knows how long I had been standing there,” she said. “I realized then that my safety was in jeopardy, and I began searching for remedies with a vengeance.”

But years after that 2005 traffic scare and many subsequent visits to doctors and sleep clinics, Brunson still lies awake in bed night after night and then is desperately sleepy during the day.

Although doctors have not definitively identified her disorder, researchers believe she suffers from non-24-hour sleep-wake disorder, or “non-24.” The chronic and little-known sleep condition is characterized by a body clock that is not aligned with a 24-hour day.

Though non-24 can affect those with normal vision, it is especially prevalent among blind people who cannot sense light, the strongest environmental signal that synchronizes the brain’s internal sleep-wake pattern to the 24-hour cycle of the Earth day.

According to the preliminary results of an ongoing clinical trial that were released earlier this summer, of the estimated 65,000 to 95,000 blind people in the United States who have sleep complaints, up to 70 percent might suffer from non-24.

“It is a devastating condition . . . because you are trying to keep a job and a social life while your body’s internal clock is competing against the 24-hour outside world,” said Harvard neuroscientist Steven W. Lockley, who is one of the principal investigators of the clinical trial.

‘Fix her!’

It was Lockley who told Brunson about non-24 at a meeting of the American Council of the Blind.

“My boss at the time, who had been hearing about my sleep problems for years, dragged me by the arm to Dr. Lockley and demanded, ‘Fix her!’ ” Brunson said.

With that introduction, Brunson, who is now the executive director of the ACB, enrolled as a participant in one of Lockley’s early studies on sleep disorders of the blind. After working with his team, she learned that her body clock ran on a cycle longer than 24 hours.

The human body clock consists of an intricate network of chemical and electrical signals controlled by two rice-grain-size structures deep in the brain. Most people’s internal clock runs slightly longer than 24 hours. However, among sighted people, the clock is reset each day by light-sensing cells in the eyes that signal to the brain that it is daytime.

For the blind, this reset mechanism fails. The resulting symptoms are similar to those experienced by sighted people who chronically disrupt their light cycle by shift work or travel across time zones.

An unrelenting cycle

Here is how it works: In theory, a blind person with an internal body clock of 24.5 hours may feel ready to fall asleep at 10:30 p.m. on Monday but not be able to fall asleep until 11 p.m. on Tuesday and not until 11:30 p.m. on Wednesday. This cycle is unrelenting, making those affected want to fall asleep later and later each day.