The health dangers of losing sleep

We all know that sleep is impor­tant for our mood, pro­duc­tiv­i­ty and gen­er­al health. But what you might not realise is how seri­ous the health impli­ca­tions of sleep­less­ness can be, par­tic­u­lar­ly for old­er peo­ple and teenagers.

Researchers at the Brigham and Women’s Hos­pi­tal in Mass­a­chu­setts found that a lack of sleep – defined as five hours’ sleep or less a night – can dou­ble an individual’s risk of demen­tia. The study, con­duct­ed among 2,812 adults aged 65 and over, also found that those get­ting less than six hours’ sleep were at greater risk of mem­o­ry loss and dif­fi­cul­ties with lan­guage and prob­lem-solv­ing com­pared with peo­ple sleep­ing for at least sev­en hours a night. 

The respon­dents were asked a range of ques­tions, cov­er­ing aspects includ­ing qual­i­ty of sleep, fre­quen­cy of awak­en­ings, inci­dence of snor­ing and reg­u­lar­i­ty of nap­ping. They then exam­ined the rela­tion­ships between these char­ac­ter­is­tics and out­comes, includ­ing inci­dent demen­tia and all-cause mor­tal­i­ty. 

Rou­tine­ly tak­ing 30 min­utes or longer to fall asleep was asso­ci­at­ed with a 45% greater risk of demen­tia. The researchers also found asso­ci­a­tions between dif­fi­cul­ty in main­tain­ing alert­ness, rou­tine nap­ping, poor-qual­i­ty sleep or sleep­ing no more than six hours a night with an increased risk of pre­ma­ture death.

“Our results showed that, among all the char­ac­ter­is­tics, short sleep dura­tion was the strongest pre­dic­tor of inci­dent demen­tia. Those sleep­ing for no more than six hours a night were at an ele­vat­ed risk,” says researcher Dr Rebec­ca Rob­bins, instruc­tor in med­i­cine at Har­vard Med­ical School and co-author of Sleep for Suc­cess! Every­thing you must know about sleep but are too tired to ask.

Sleep and mental health

Sleep experts at the Uni­ver­si­ty of South Aus­tralia, Ade­laide, believe that both par­ents and med­ical prac­ti­tion­ers need to improve their aware­ness of the rela­tion­ship between sleep and men­tal health in teenagers. 

Dr Alex Agos­ti­ni, a lec­tur­er at the uni­ver­si­ty, observes that sleep is espe­cial­ly impor­tant for peo­ple in this age group because they are going through a range of poten­tial­ly stress­ful phys­i­cal and devel­op­men­tal changes.

A teenag­er reg­u­lar­ly get­ting less than six hours’ sleep a night is twice as like­ly as aver­age to engage in risky behav­iour such as dan­ger­ous dri­ving and drug abuse, accord­ing to the researchers.

Attributing cause

While stud­ies show clear cor­re­la­tions between a lack of sleep and health prob­lems, sci­en­tists acknowl­edge that estab­lish­ing causal links is a hard­er task. Pro­fes­sor Derk-Jan Dijk is direc­tor of the Uni­ver­si­ty of Surrey’s sleep research cen­tre and a for­mer asso­ciate neu­ro­sci­en­tist at the Brigham and Wom­en’s Hos­pi­tal. He notes that attribut­ing caus­es for demen­tia, for instance, is com­plex, not least because of the pos­si­bil­i­ty of reverse causal­i­ty.

“If there is some­thing wrong with a person’s brain, it could affect their sleep,” he explains. “But yes, extreme sleep pat­terns and dis­or­ders are asso­ci­at­ed with adverse health out­comes, includ­ing demen­tia.”

Tim Bean­land, head of knowl­edge man­age­ment at the Alzheimer’s Soci­ety, also observes that the rela­tion­ship between sleep depri­va­tion and demen­tia is com­plex. Dif­fer­ent types of demen­tia are asso­ci­at­ed with dif­fer­ent sleep prob­lems, he adds. 

“Researchers are not yet sure which way the inter­ac­tion goes – whether poor sleep caus­es or exac­er­bates demen­tia, or if demen­tia leads to poor sleep,” Bean­land says. “Some researchers believe that both of these the­o­ries could be true and the rela­tion­ship could be cir­cu­lar. On top of this, the mech­a­nisms that under­lie these inter­ac­tions are unclear. More research is need­ed, par­tic­u­lar­ly stud­ies that observe large groups of affect­ed peo­ple for long peri­ods.”

Recent research sug­gests that the glym­phat­ic sys­tem – a net­work of ves­sels that clears waste chem­i­cals from the cen­tral ner­vous sys­tem, most­ly dur­ing sleep – may be dis­rupt­ed by, and con­tribute to, some dis­eases of the brain.

Dis­turbed sleep is also a risk fac­tor for numer­ous oth­er health issues. Dis­or­ders such as sleep apnoea, when breath­ing repeat­ed­ly stops, may increase the risk of cog­ni­tive decline, while the impact of both very short and long sleep dura­tion have been report­ed for many oth­er health out­comes.

How to get enough sleep

Sim­ply going to bed ear­li­er may not be the answer to get­ting enough sleep, accord­ing to Dijk. He believes that the most effec­tive solu­tion is to find the “sweet spot” – the best time to go to bed for unin­ter­rupt­ed, high-qual­i­ty sleep. 

“We all accept that insuf­fi­cient sleep is not good for our brain func­tion – we know that we may not per­form well if we don’t sleep well,” he says. “But there’s no bet­ter way to ruin your sleep than by spend­ing too much time in bed. For exam­ple, peo­ple who go to bed too ear­ly are like­ly to have their sleep inter­rupt­ed.”

Day­time nap­ping, while not always a bad thing, does not make up for a poor night’s sleep, says Dijk, who adds: “There are cer­tain­ly healthy nap­pers, but it’s a bit of a mis­rep­re­sen­ta­tion to say that nap­ping is a good thing. Healthy old­er peo­ple should not be sleep­ing dur­ing the day. If you’re doing that, you’re not get­ting enough sleep at night, or there’s anoth­er health prob­lem.”

If nap­ping is not the answer, could sleep­ing tablets be? Refer­ring to anoth­er study run by the Brigham and Wom­en’s Hos­pi­tal team, Rob­bins sug­gests that the answer is no. In an analy­sis of med­ica­tion usage among old­er peo­ple in the US, this research found that 15% of the sam­ple rou­tine­ly con­sumed sleep med­ica­tion. This usage was asso­ci­at­ed with inci­dent demen­tia across the fol­low-up inter­val.

While peo­ple might be tempt­ed to use week­ends to catch up on their sleep, get­ting a reg­u­lar sev­en-plus hours’ worth is more impor­tant, par­tic­u­lar­ly for teenagers, accord­ing to Agos­ti­ni.

“There are so many rea­sons why it is health­i­er to min­imise sleep loss by reg­u­lar­ly going to bed a lit­tle ear­li­er through­out the week than it is by try­ing to make it up over the week­end,” she says. “I don’t rec­om­mend a delay in wake times of more than an hour on Sat­ur­day and Sun­day morn­ings.”