Blind people often find it hard to align their sleep-wake cycle with a 24-hour day. (Michael Morgenstern/FOR THE WASHINGTON POST)

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.

“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.

For Brunson, the waves of disturbed sleep typically occur in three- or four-week episodes of insomnia that cause her to wake up between 1 and 2 in the morning, regardless of when she goes to bed.

Jack Mendez, a 35-year-old information technology professional who learned last year that he has non-24, often finds himself awaking between 2 a.m. and 5:30 a.m., unable to fall back to sleep. On the evening that he spoke with a Post reporter, he had been awake since 3 in the morning.

Some who suffer from non-24 have found limited relief through treatment with synthetic versions of the hormone melatonin, which works to drag forward the body clock’s reset time by providing a chemical pulse to the brain that signals nighttime.

Synthetic doses of melatonin help alleviate Brunson’s non-24, but the treatment does not work at all for Mendez.

“It gives me nightmares and cold sweats, and I feel hung over the next day,” he said.

Shuttled from doctor to doctor as a child, Mendez has been prescribed everything from sleeping pills to psychotropic drugs. Thus far, he has found no treatments that help. He praises his fiancee for her patience in tolerating their often opposite sleeping schedules.

Testing a treatment

There are no FDA-approved medications to treat non-24. However, the ongoing clinical trial has advanced from screening participants for non-24 to testing a candidate drug called tasimelteon. The drug, which is intended to treat non-24 and other circadian rhythm sleep disorders, is being developed by District-based Vanda Pharmaceuticals.

Vanda scientists hope that tasimelteon, which has a similar molecular structure to melatonin, will have superior beneficial effects. Synthetic melatonin itself is classified as a dietary supplement.

Northwestern University professor Phyllis Zee, a neuroscientist and sleep specialist who was not involved in Vanda’s research, said that tasimelteon’s long-term effects remain unclear, but at the very least the trial is valuable in raising awareness about and creating a better understanding of the condition.

“Most physicians and blind patients are unfamiliar with non-24, and a large-scale study of the totally blind is crucial in developing criteria for diagnosis,” she said.

Although Brunson and Mendez both participated in the screening phase of the tasimelteon trial, neither of them chose to take the drug because they were wary of its impact on job performance and its interactions with other medications.

But Mendez, who is at the Louisiana Center for the Blind finishing a nine-month training program that will help him travel and work more independently, plans to rejoin the trial and try tasimelteon after his course ends.

“The training has helped me learn to think about blindness as just a characteristic, not as a thing that consumes my life,” he said. “Of course, a good sleep helps with that thinking, too.”