Does midlife obe­sity pro­tect against de­men­tia?


Peo­ple who are obese in mid­dle age run a lower risk of de­vel­op­ing de­men­tia later, said a large and long-term study Fri­day whose find­ings chal­lenge the pre­vail­ing wis­dom.

On the other end of the scale, how­ever, be­ing un­der­weight in the 40-55 age bracket was as­so­ci­ated with a higher risk, the re­searchers found.

While ad­mit­ting they were “sur­prised” by the po­ten­tial protective ef­fect of obe­sity, the team cau­tioned against jump­ing to con­clu­sions.

The rea­sons for the ob­served as­so­ci­a­tion were not known, they wrote in the jour­nal The Lancet Di­a­betes & En­docrinol­ogy.

“The mes­sage that peo­ple shouldn’t take away is that it’s OK to be over­weight or obese,” study co-au­thor Nawab Qizil­bash of the OXON Epi­demi­ol­ogy re­search com­pany told AFP by tele­phone from Madrid.

“We do know ... that if you are over­weight or obese you have a high risk of (early) death, so it is not clear that the net ben­e­fit on de­men­tia would be pos­i­tive.

‘You may not live long enough

to get the ben­e­fit’

“In other words, even if there were to be protective ef­fects on de­men­tia from be­ing over­weight or obese, you may not live long enough to get the ben­e­fit of it.”

But the widely-held be­lief that re­duc­ing obe­sity in mid­dle age could help pre­vent de­men­tia may also be ill-founded, said the team, and re­quired a re­think of how we iden­tify high-risk in­di­vid­u­als.

The re­searchers combed a Bri­tish data­base of pa­tient in­for­ma­tion recorded from 1992 to 2007, rep­re­sent­ing some nine per­cent of the UK pop­u­la­tion.

In what they claimed was the largest-ever study of any link be­tween body­weight and de­men­tia risk, the team an­a­lyzed the med­i­cal records of nearly two mil­lion 40-plussers.

They com­pared


pa­tients’ BMI (body weight in­dex, a ra­tio of weight to height) to how many de­vel­oped de­men­tia later on.

A BMI of 25 and higher is clas­si­fied over­weight, and 30 and over obese. Any­thing less than 18.5 is gen­er­ally con­sid­ered un­der­weight, though for this study the re­searchers set the bar at 20.

Over two decades, the re­searchers found, “the in­ci­dence of de­men­tia con­tin­ued to fall for ev­ery in­creas­ing BMI cat­e­gory with very obese peo­ple (a BMI over 40) hav­ing a 29 per­cent lower de­men­tia risk than peo­ple of a healthy weight.”

Just over 45,500 of the to­tal study group de­vel­oped de­men­tia.

“Com­pared with peo­ple of a healthy weight, un­der­weight peo­ple ( BMI un­der 20) had a 34 per­cent higher risk of de­men­tia,” added the au­thors.

The un­der­weight cat­e­gory is a wide one, rang­ing from lean to skele­tal, said Qizil­bash, who de­scribed the in­creased risk as “sig­nif­i­cant.”

‘We were sur­prised’

Nu­mer­ous other stud­ies, in­clud­ing one car­ried by The Lancet Neu­rol­ogy in July 2014, have linked obe­sity to a higher risk for Alzheimer’s Dis­ease and other forms of de­men­tia.

But Qizil­bash said most were “fairly small and sta­tis­ti­cally un­re­li­able.”

“We were sur­prised about the find­ings. Be­cause most of them, not unan­i­mously but the ma­jor­ity of pre­vi­ous stud­ies, have tended to in­di­cate that peo­ple who are over­weight or obese in mid­dle age have an in­creased risk of de­men­tia in older age.”

Fur­ther re­search was needed to con­firm the link and find an ex­pla­na­tion for it, the re­searcher added.

“There are some po­ten­tial con­tenders, par­tic­u­larly in terms of the role that nu­tri­ents may play,” he said.

The team hoped their re­sults would aid in the search for “protective fac­tors” with a view to new treat­ments.



In­terna- tional (ADI) projects the num­ber of peo­ple with de­men­tia will rise from 35.6 mil­lion in 2010 to 65.7 mil­lion by 2030 and 115.4 mil­lion by 2050.

Obe­sity, too, is soar­ing, hav­ing more than dou­bled world­wide since 1980. By 2014, more than 1.9 bil­lion adults were over­weight, of whom 600 mil­lion were obese, ac­cord­ing to the World Health Or­ga­ni­za­tion.

In a com­ment also car­ried by The Lancet, neu­rol­ogy pro­fes­sor Deb­o­rah Gustafson said the find­ings should be in­ter­preted “with care.”

“The re­port by Qizil­bash and col­leagues is not the fi­nal word on this con­tro­ver­sial topic,” she wrote.

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