This weekend marks daylight saving time, when many people grumble about losing an hour of sleep as clocks are turned ahead.

But most of us aren't getting enough shut-eye to begin with, and experts say that can play havoc with our health. Sleep is linked to everything from high blood pressure to diabetes to obesity and even car accidents.

Earlier this month, the National Sleep Foundation -- an Arlington, Va.-based nonprofit -- released a study asking pilots and other transportation professionals about their sleep habits. Alarmingly, 20 percent of surveyed pilots said they have made a "serious error" due to sleepiness and 18 percent of train operators surveyed said they have had a "near miss" due to sleepiness, as did 14 percent of truck drivers.

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Daylight saving time starts Sunday at 2 a.m. Don't forget to turn your clocks ahead an hour.

But it's not just pilots who make mistakes when they're tired, said Dr. Richard Levin, chief of otolaryngology, an ears, nose and throat specialty, at St. Vincent's Medical Center in Bridgeport. "Two of the biggest effects of not getting enough sleep are inattentiveness and impaired alertness and productivity," he said. "This can affect our daily activities and make us more prone to accidents."

According to the Centers for Disease Control and Prevention, adults need seven to nine hours of sleep a night. Kids need more -- around 10 to 11 hours for children ages 5 to 10 and roughly nine hours for ages 10 to 17. Yet most of us aren't getting nearly that amount.

The CDC's National Health Interview Survey, conducted in 2005 through 2007, showed that 30 percent of adults surveyed got less than six hours of sleep.

In addition to making us less productive and worse at operating machinery, inadequate sleep can weaken the immune system and put people at higher risk for hypertension, diabetes and other health problems. It can also lead to weight gain, Levin said.

"People who are not getting enough sleep tend to have food cravings," he said, adding that the cravings might be linked to the irritability many of us experience when we're sleep-deprived. "It's almost like a pacifier effect."

But what causes this epidemic of people lurching zombie-like through life and putting their health at risk? There are a number of possible contributors, Kryger said. It could be something relatively simple, like an overconsumption of caffeine, or working multiple jobs. Sometimes it's just a matter of will.

"A lot of people choose to be sleep-deprived," Kryger said. "They go to bed late, wake up early and don't function well."

That's particularly common among teens, he said. In these cases, you just have to hope the person realizes the error of their ways.

But it might be more than stubbornness or too much coffee keeping you awake at night. The CDC reports that anywhere from 50 million to 70 million adults have sleep or wakefulness disorders. These include sleep apnea, a relatively common disorder in which the sufferer has one or more pauses in breathing, or shallow breaths, while sleeping. Other contributors to sleeplessness can include depression or taking certain medications, including antidepressants.

If there's not an easy explanation for sleeplessness, a visit to a sleep specialist could be in order, Kryger said. Several area hospitals have sleep centers, including Bridgeport Hospital and Yale-New Haven Hospital. Though a lot of sleeplessness can be changed by lifestyle adjustments, Kryger said, that's not always the case.

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