Hav­ing more kids tied to lower odds of Alzheimer’s in women

The Borneo Post - Nature and health - - Vital Signs -

A WOMAN’S fer­til­ity might help pre­dict how likely she is to de­velop de­men­tia later in life, two new stud­ies sug­gest. Women who were very fer­tile ap­peared to have some pro­tec­tion against de­men­tia, a Kaiser Per­ma­nente study found. This in­cluded women who had more chil­dren, more years of fer­til­ity, and men­stru­a­tion that started ear­lier and ended later in their lives, ex­plained lead re­searcher Paola Gil­sanz. She is a staff sci­en­tist with the Kaiser Per­ma­nente North­ern Cal­i­for­nia divi­sion of re­search.

A sec­ond study, from the Univer­sity of Cal­i­for­nia, Los An­ge­les, found that women who ex­pe­ri­enced more months of pregnancy dur­ing their lives had a lower risk of Alzheimer’s disease. Both stud­ies were to be pre­sented at the Alzheimer’s As­so­ci­a­tion an­nual meet­ing, in Chicago. Such re­search is con­sid­ered pre­lim­i­nary un­til pub­lished in a peer-re­viewed jour­nal, and these stud­ies did not prove that in­fer­til­ity causes de­men­tia risk to rise.

There’s been a lot of in­ter­est in sex-spe­cific fac­tors that could in­flu­ence de­men­tia risk, Gil­sanz noted. Al­most two-thirds of Amer­i­cans with Alzheimer’s are women, ac­cord­ing to the Alzheimer’s As­so­ci­a­tion. “More women than men get de­men­tia, and for a while it was thought be­cause women were liv­ing longer. Now re­search is show­ing that’s not the whole story,” Gil­sanz said. “Now we’re ask­ing, what is it about the bi­ol­ogy of be­ing a woman that could po­ten­tially mod­u­late the risk of de­men­tia?”

Kaiser Per­ma­nente re­searchers re­viewed the health records of 14,595 women who were aged 40 to 55 be­tween 1964 and 1973, to see if there were any as­so­ci­a­tions be­tween their re­pro­duc­tive his­tory and de­men­tia risk. The in­ves­ti­ga­tors found that women with three or more chil­dren had a 12 per cent lower risk of de­men­tia than women with one child.

Fur­ther, the length of a woman’s re­pro­duc­tive pe­riod -- the years dur­ing which she men­stru­ates -- ap­peared to be tied to de­men­tia risk:

- Women with re­pro­duc­tive pe­ri­ods of 21 to 30 years were at 33 per cent el­e­vated risk of de­men­tia, com­pared to women who were fer­tile 38 to 44 years.

- Women who ex­pe­ri­enced their first men­strual pe­riod at age 16 or older were at 31 per cent greater risk of de­men­tia than those who re­ported their first men­strual pe­riod at age 13.

- Women who un­der­went nat­u­ral menopause at age 45 or ear­lier were at 28 per cent greater risk of de­men­tia than those who had their last men­strual pe­riod later than age 45.

No one can say for cer­tain why fer­til­ity is associated with de­creased de­men­tia risk, Gil­sanz said. “There’s some promis­ing re­search about oe­stro­gen and how it may play a role in de­men­tia,” Gil­sanz noted. “An­i­mal mod­els have shown oe­stro­gen might play a pro­tec­tive role.” The sec­ond study, which looked at 133 el­derly Bri­tish women, found that those who spent more of their lives preg­nant were less likely to de­velop Alzheimer’s. Women had a 5.5 per cent de­crease in Alzheimer’s risk for ev­ery month they were preg­nant, the re­searchers found. In this case, the re­searchers hy­poth­e­sised that the ben­e­fi­cial ef­fects of pregnancy on the im­mune sys­tem could play some role in fu­ture brain health. The study’s lead re­searcher, Molly Fox, said, “We are in­trigued by the pos­si­bil­ity that pregnancy may re­or­gan­ise the mother’s body in ways that could pro­tect her against de­vel­op­ing Alzheimer’s later in life.”

Fox is an as­sis­tant pro­fes­sor of an­thro­pol­ogy and psy­chi­a­try & biobe­havioural sciences at UCLA. “These re­sults also sug­gest that the story might not be so sim­ple as be­ing all about es­tro­gen ex­po­sure, as pre­vi­ous re­searchers have sug­gested,” Fox said in a state­ment.

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