Study: Practice effect due to repeated testing can delay detection of cognitive impairment and dementia

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Prac­tice Imper­fect: Repeat­ed Cog­ni­tive Test­ing Can Obscure Ear­ly Signs of Demen­tia (UC San Diego Health press release):

“Alzheimer’s dis­ease (AD) is a pro­gres­sive, neu­rode­gen­er­a­tive con­di­tion that often begins with mild cog­ni­tive impair­ment or MCI, mak­ing ear­ly and repeat­ed assess­ments of cog­ni­tive change cru­cial to diag­no­sis and treatment.

But in a paper pub­lished online in the jour­nal Alzheimer’s & Demen­tia: Diag­no­sis, Assess­ment & Dis­ease Mon­i­tor­ing, a team of researchers led by sci­en­tists at the Uni­ver­si­ty of Cal­i­for­nia San Diego School of Med­i­cine found that repeat­ed test­ing of mid­dle-age men pro­duced a “prac­tice effect” which obscured true cog­ni­tive decline and delayed detec­tion of MCI.

“When per­sons take the same or sim­i­lar tests repeat­ed­ly over time, they sim­ply get bet­ter at tak­ing the tests,” said first author Jere­my A. Elman, PhD, a post­doc­tor­al fel­low in the lab of senior author William S. Kre­men, PhD, pro­fes­sor of psy­chi­a­try and co-direc­tor with Car­ol E. Franz, PhD, of the Cen­ter for Behav­ior Genet­ics of Aging at UC San Diego School of Med­i­cine. “The con­se­quence is that their results may not accu­rate­ly reflect the real­i­ty of their condition.”

The Study:

Under­diag­no­sis of mild cog­ni­tive impair­ment: A con­se­quence of ignor­ing prac­tice effects (Alzheimer’s & Demen­tia: Diag­nos­tic Assess­ment & Prog­no­sis). From the abstract:

  • Intro­duc­tion: Lon­gi­tu­di­nal test­ing is nec­es­sary to accu­rate­ly mea­sure cog­ni­tive change. How­ev­er, repeat­ed test­ing is sus­cep­ti­ble to prac­tice effects, which may obscure true cog­ni­tive decline and delay detec­tion of mild cog­ni­tive impair­ment (MCI).
  • Meth­ods: We retest­ed 995 late-mid­dle-aged men in a ?6‑year fol­low-up of the Viet­nam Era Twin Study of Aging. In addi­tion, 170 age-matched replace­ments were test­ed for the first time at study wave 2. Group dif­fer­ences were used to cal­cu­late prac­tice effects after con­trol­ling for attri­tion effects. MCI diag­noses were gen­er­at­ed from prac­tice-adjust­ed scores.
  • Results: There were sig­nif­i­cant prac­tice effects on most cog­ni­tive domains. Con­ver­sion to MCI dou­bled after cor­rect­ing for prac­tice effects, from 4.5% to 9%…

The Study in Context: