25% over age 70 have OSA

INSOMNIA: When sleep becomes a tough task
Published: 2009/09/16 12:53:04 PM



CATCHING SOME SHUT-EYE: As you get older the quality of your sleep deteriorates dramatically. That is especially true of delta sleep, a form of non-REM sleep, which is the deepest, most restful sleep you can get, say doctors. Experts estimate that up to 95% of people with at least one sleep disorder go undiagnosed. Picture: CLAUDIA MEYER/STOCK.XCHNG


IF YOU are finding that it is no longer as easy to sleep like a baby as it was when you were younger, you are not alone.



As you age, sleep quality deteriorates dramatically. The biggest decline is in what the experts call slow-wave sleep, also called delta sleep. By the time you are 70, delta sleep has become almost completely extinguished.



That can be a problem because delta sleep, a form of non-REM (rapid eye movement) sleep, is the deepest, most restful sleep you can get, says Dr Brian Bohner, co- medical director of the US Sleep Centres at Northwest Hospital in Maryland and Sinai Hospital in Baltimore.



To put things in perspective, delta sleep makes up about 25% of a 25-year-old’s sleep but only about 3% of the sleep of someone who is 60.



Because a decline in sleep quality is so common with age, the average person doesn’t know about options to improve rest at night. Experts estimate that up to 95% of people with at least one sleep disorder go undiagnosed.



“Older patients may not actually need a sleep study,” says Bohner. “Sometimes we can find and solve the problem simply by having them come in for a consultation and going through their medical histories.”



The most common sleep problem that Bohner sees in the elderly population is insomnia, which is often caused by arthritis pain, acid reflux or heart problems or because of certain medications such as beta-blockers and steroids.



“Many times, we can just adjust a patient’s medication regimen to eliminate the insomnia,” Bohner says. Also, caffeine, alcohol and tobacco all cause sleep disturbances, so patients may need to change some of their habits to get the sleep they need.



“Obstructive sleep apnea is found in about 25% of the population aged 70 and over,” says Bohner. Sleep apnea, which is three times more prevalent in younger men than in younger women, becomes more common among women as they age.



Oestrogen helps control breathing, so after menopause a decline in this hormone leads to the same percentage of women and men with sleep apnea.



“About 10% of older patients also suffer from restless leg syndrome, or RLS,” says Bohner. “Sometimes a patient’s symptoms aren’t obvious, but they will tell me, ‘I can't sleep because my legs feel weird’.



“Well, that’s RLS, and there are medications that can effectively control it.”



Medication may also be prescribed for REM disorder and advanced sleep phase syndrome. REM disorder is when people act out their dreams.



This can be dangerous for elderly people who have a greater potential for falls, says Bohner.



Advanced sleep phase syndrome is when the body’s internal clock changes so that the older person wants to go to bed earlier and wake up at a much earlier time. It’s not necessarily a bad thing, says Bohner, but some people may want to fix this so they can be awake at the same time as the rest of society.



If you or elderly family members are experiencing increased disturbance of sleep, he suggests you call a sleep clinic for a consultation.



“Regardless of your age, never accept that your sleep quality cannot be improved,” says Bohner.







What is sleep?



Bats, birds, box turtles, humans and many other animals have at least one thing in common: they sleep. Humans, in fact, spend roughly a third of their lives asleep, but sleep researchers still don’t know why.



According to recent research, the function of sleep is one of the 125 greatest unsolved mysteries in science. Theories range from brain “maintenance” — including memory consolidation and pruning — to reversing damage from oxidative stress suffered while awake, to promoting longevity.



None of these theories is well established, and many are mutually exclusive.



Now, a new analysis by Dr Jerome Siegel, University of California Los Angeles professor of psychiatry and director of the university’s Centre for Sleep Research, shows that sleep’s primary function is to increase animals’ efficiency and minimise their risk by regulating the duration and timing of their behaviour.



The research appears online in the journal Nature Reviews Neuroscience.



“Sleep has normally been viewed as something negative for survival because sleeping animals may be vulnerable to predation and they can’t perform the behaviours that ensure survival,” Siegel says.



These behaviours include eating, procreating, caring for family members, monitoring the environment for danger and scouting for prey.



“So it’s been thought that sleep must serve some as yet unidentified physiological or neural function that can’t be accomplished when animals are awake,” he says.



Siegel’s lab conducted a new survey of the sleep times of a broad range of animals, examining everything from the platypus and the walrus to the echidna, a small, burrowing, egg-laying mammal covered in spines. The researchers concluded that sleep itself is highly adaptive, much like the inactive states seen in a wide range of species, starting with plants and simple microorganisms.



These species have dormant states — as opposed to sleep — even though in many cases they do not have nervous systems. That challenges the idea that sleep is for the brain, says Siegel.



“We see sleep as lying on a continuum that ranges from these dormant states like torpor and hibernation, on to periods of continuous activity without any sleep, such as during migration, where birds can fly for days on end without stopping,” he says.



Hibernation is one example of an activity that regulates behaviour for survival. A small animal, Siegel says, can’t migrate to a warmer climate in winter. So it hibernates, effectively cutting its energy consumption and its need for food, remaining secure from predators by burrowing underground.



Sleep duration, then, is determined in each species by the time requirements of eating, the cost-benefit relations between activity and risk, migration needs, care of young, and other factors.



However, unlike hibernation and torpor, Siegel says, sleep is rapidly reversible — that is, animals can wake up quickly, a unique mammalian adaptation that allows for a relatively quick response to sensory signals.



Humans fit into this analysis as well. What is most remarkable about sleep, according to Siegel, is not the unresponsiveness or vulnerability it creates but rather the ability to reduce body and brain metabolism while still allowing that high level of responsiveness to the environment.



“The often cited example is that of a parent arousing at a baby’s whimper but sleeping through a thunderstorm,” he says. “That dramatises the ability of the sleeping human brain to continuously process sensory signals and trigger complete awakening to significant stimuli within a few hundred milliseconds.”



In humans, the brain constitutes, on average, just 2% of total body weight but consumes 20% of the energy used during quiet waking, so these savings have considerable adaptive significance. Besides conserving energy, sleep invokes survival benefits for humans too — “for example,” says Siegel, “a reduced risk of injury, reduced resource consumption and, from an evolutionary standpoint, reduced risk of detection by predators.



“This Darwinian perspective can explain age-related changes in human sleep patterns as well,” he says. “We sleep more deeply when we are young, because we have a high metabolic rate that is greatly reduced during sleep, but also because there are people to protect us. Our sleep patterns change when we are older, though, because that metabolic rate reduces and we are now the ones doing the alerting and protecting from dangers.”
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