Late On­set, Slower Pro­gres­sion Alzheimers

Late On­set, Slower Pro­gres­sion

Wellness Update - - Contents -

The great­est risk fac­tor for Alzheimer’s disease (AD) is ad­vanc­ing age. By age 85, the like­li­hood of de­vel­op­ing the dreaded neu­ro­log­i­cal dis­or­der is roughly 50 per­cent.

T he great­est risk fac­tor for Alzheimer’s disease (AD) is ad­vanc­ing age. By age 85, the like­li­hood of de­vel­op­ing the dreaded neu­ro­log­i­cal dis­or­der is roughly 50 per­cent. But re­searchers at the Univer­sity of Cal­i­for­nia, San Diego School of Medicine say AD hits hard­est among the “younger el­derly” – peo­ple in their 60s and 70s – who show faster rates of brain tis­sue loss and cog­ni­tive de­cline than AD pa­tients 80 years and older. The find­ings, re­ported online in the Au­gust 2, 2012 is­sue of the jour­nal PLOS One, have pro­found im­pli­ca­tions for both di­ag­nos­ing AD – which cur­rently af­flicts an es­ti­mated 5.6 mil­lion Amer­i­cans, a num­ber pro­jected to triple by 2050 – and ef­forts to find new treat­ments. There is no cure for AD and ex­ist­ing ther­a­pies do not slow or stop disease pro­gres­sion. “One of the key fea­tures for the clin­i­cal de­ter­mi­na­tion of AD is its re­lent­less pro­gres­sive course,” said Do­minic Hol­land, PhD, a re­searcher at the Depart­ment of Neu­ro­sciences at UC San Diego who led the study and the is the pa­per’s first au­thor. “Pa­tients typ­i­cally show marked de­te­ri­o­ra­tion year af­ter year. If older pa­tients are not show­ing the same de­te­ri­o­ra­tion from one year to the next, doc­tors may be hes­i­tant to di­ag­nose AD, and thus th­ese pa­tients may not re­ceive ap­pro­pri­ate care, which can be very im­por­tant for their qual­ity of life.” Hol­land and col­leagues used imaging and biomarker data from par­tic­i­pants in the Alzheimer’s Disease Neu­roimag­ing Ini­tia­tive, a multi-in­sti­tu­tion ef­fort co­or­di­nated at UC San Diego. They ex­am­ined 723 peo­ple, ages 65 to 90 years, who were cat­e­go­rized as ei­ther cog­ni­tively nor­mal, with mild cog­ni­tive im­pair­ment (an in­ter­me­di­ate stage be­tween nor­mal, age-re­lated cog­ni­tive de­cline and de­men­tia) or suf­fer­ing from full-blown AD. “We found that younger el­derly show higher rates of cog­ni­tive de­cline and faster rates of tis­sue loss in brain re­gions that are vul­ner­a­ble dur­ing the early stages of AD,” said Hol­land. “ Ad­di­tion­ally cere­brospinal fluid biomarker lev­els in­di­cate a greater disease bur­den in younger than in older in­di­vid­u­als.” Hol­land said it’s not clear why AD is more ag­gres­sive among younger el­derly. “It may be that pa­tients who show on­set of de­men­tia at an older age, and are de­clin­ing slowly, have been de­clin­ing at that rate for a long time,” said se­nior au­thor Linda McEvoy, PhD, as­so­ci­ate pro­fes­sor of ra­di­ol­ogy. “But be­cause of cog­ni­tive re­serve or other still-un­known fac­tors that pro­vide ‘re­sis­tance’ against brain dam­age, clin­i­cal symp­toms do not man­i­fest till later age.” Another pos­si­bil­ity, ac­cord­ing to Hol­land, is that older pa­tients may be suf­fer­ing from mixed de­men­tia – a com­bi­na­tion of AD pathol­ogy and other neu­ro­log­i­cal con­di­tions. Th­ese pa­tients might with­stand the ef­fects of AD un­til other ad­verse fac­tors, such as brain le­sions caused by cere­brovas­cu­lar disease, take hold. At the mo­ment, AD can only be di­ag­nosed defini­tively by an au­topsy. “So we do not yet know the un­der­ly­ing neu­ropathol­ogy of par­tic­i­pants in this study,” Hol­land said. Clin­i­cal tri­als to find new treat­ments for AD may be im­pacted by the dif­fer­ing rates, re­searchers said. “Our re­sults show that if clin­i­cal tri­als of can­di­date ther­a­pies pre­dom­i­nately en­roll older el­derly, who show slower rates of change over time, the abil­ity of a ther­apy to suc­cess­fully slow disease pro­gres­sion may not be rec­og­nized, lead­ing to fail­ure of the clin­i­cal trial,” said Hol­land. “Thus, it’s crit­i­cal to take into ac­count age as a fac­tor when en­rolling sub­jects for AD clin­i­cal tri­als.” The ob­vi­ous down­side of the find­ings is that younger pa­tients with AD lose more of their pro­duc­tive years to the disease, Hol­land noted. “The good news in all of this is that our re­sults in­di­cate those who sur­vive into the later years be­fore show­ing symp­toms of AD will ex­pe­ri­ence a less ag­gres­sive form of the disease.”

This in­for­ma­tion pro­vided cour­tesy of UC San Diego Health Sys­tem

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