Study links fac­tors in en­vi­ron­ment with autism

Sci­en­tists ex­am­ined baby teeth from twins

The Washington Times Daily - - NATION - BY LAURA KELLY

Sci­en­tists an­a­lyz­ing min­eral de­posits in the baby teeth of twins, where one of whom had autism, found a dis­crep­ancy in heavy met­als and nu­tri­ents. This dis­cov­ery adds sup­port to the ar­gu­ment that the en­vi­ron­ment, as much as genes, can lead to the dis­or­der.

The teeth of the chil­dren with autism were found to have higher amounts of lead and lower lev­els of man­ganese — tox­ins known to con­trib­ute to at­ten­tion and be­hav­ioral dis­or­ders — and an in­con­sis­tent ab­sorp­tion of zinc, a min­eral es­sen­tial to proper health and devel­op­ment.

The study was pub­lished Thurs­day in the jour­nal Na­ture Com­mu­ni­ca­tions and was con­ducted by re­searchers in the U.S. and Swe­den with sup­port from the Na­tional In­sti­tutes of Health.

The Cen­ters for Dis­ease Con­trol and Preven­tion es­ti­mates that 1-in-68 chil­dren have autism spec­trum dis­or­der (ASD). Autism is about 4 1/2 times more com­mon in boys than girls.

Peo­ple with autism have dif­fi­culty in­ter­act­ing phys­i­cally and emo­tion­ally with oth­ers and the world around them. Symp­toms in­clude a sen­si­tiv­ity to ex­ter­nal stim­uli, such as bright lights and loud sounds, which can pro­duce anx­i­ety or anx­ious be­hav­ior.

There is a grow­ing preva­lence of ASD and while sci­en­tists at­tribute the higher num­bers to be­com­ing more skilled at di­ag­no­sis, they also ac­knowl­edge that the in­creas­ing fre­quency is hap­pen­ing at greater rates than can be at­trib­uted to genes and in­creased di­ag­nos­tics alone.

“I think there is con­sen­sus in the sci­en­tific com­mu­nity that the preva­lence of autism is in­creas­ing and our genes don’t change so quickly,” said Man­ish Arora, an en­vi­ron­men­tal sci­en­tist and den­tist at the Ic­ahn School of Medicine at Mount Si­nai in New York and lead au­thor of the study. “Es­sen­tially there are en­vi­ron­men­tal driv­ers for autism that are in­ter­act­ing with our ge­netic makeup.”

Com­par­ing identical and fra­ter­nal twins where one si­b­ling had autism al­lowed sci­en­tists to con­trol the ge­netic fac­tors. Al­though find­ing the sam­ples proved dif­fi­cult enough in it­self, Dr. Arora said.

The sci­en­tists worked from the Swedish Roots of Autism and ADHD Twin Study, which had been col­lect­ing sam­ples from twins where one si­b­ling is autis­tic.

The study in­cluded 32 com­plete twin pairs and 12 in­di­vid­u­als from twin pairs whose si­b­ling did not donate a tooth.

“So these are very rare and very pre­cious sam­ples,” Dr. Arora said.

Us­ing ad­vanced laser tech­nol­ogy, the re­searchers were able to eval­u­ate baby teeth much like rings of a tree are stud­ied, Dr. Arora said, and were able to recre­ate the pre­na­tal en­vi­ron­ment.

“We de­vel­oped a method us­ing lasers where we can start map­ping the en­vi­ron­ment, but the en­vi­ron­ment even be­fore they were born,” he said.

Re­searchers used a tooth-ma­trix biomarker to ex­am­ine pre- and post-natal lev­els of cer­tain min­er­als, in­clud­ing zinc, man­ganese and lead among the “growth rings in teeth,” which start to form be­gin­ning in the sec­ond trimester.

They found that the dif­fer­ences in the up­takes of the met­als were most prom­i­nent dur­ing the pe­ri­ods just be­fore and af­ter birth.

“We think autism be­gins very early, most likely in the womb, and re­search sug­gests that our en­vi­ron­ment can in­crease a child’s risk,” said Cindy Lawler, head of the Genes, En­vi­ron­ment, and Health Branch of the Na­tional In­sti­tute of En­vi­ron­men­tal Health Sciences. “But by the time chil­dren are di­ag­nosed at age three or four, it’s hard to go back and know what the moms were ex­posed to. With baby teeth, we can ac­tu­ally do that.”

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