In APOE ε4 Carriers, Odor Sensitivity Declines at Earlier Age

WEDNESDAY, July 26, 2023 (HealthDay News) -- For apolipoprotein E (APOE) ε4 carriers, odor sensitivity declines at an earlier age than odor identification or cognition, according to a study published online July 26 in Neurology.

Matthew GoodSmith, M.D., from The University of Chicago, and colleagues compared odor sensitivity and identification among APOE ε4 carriers and noncarriers stratified by age in the National Social Life Health and Aging Project, a nationally representative survey study of home-dwelling U.S. older adults. Odor sensitivity, odor identification, and cognition were measured in 865; 1,156; and 864 respondents, respectively; all had genetic data available.

The researchers found that odor sensitivity deficits were apparent at ages 65 to 69 years in APOE ε4 carriers, while deficits in odor identification did not appear until ages 75 to 79 years. Compared with noncarriers, in APOE ε4 carriers, odor sensitivity did not decline more rapidly with aging (carrier status and aging interaction: odds ratio, 1.44; 95 percent confidence interval, 0.94 to 2.19; P = 0.092), while odor identification declined more rapidly in carriers (aging 10 years interaction: odds ratio, 0.26; 95 percent confidence interval, 0.13 to 0.52; P < 0.001). In parallel to odor identification, cognition declined more rapidly in carriers (interaction: odds ratio, 0.55; 95 percent confidence interval, 0.34 to 0.89; P = 0.015).

"We present evidence that APOE ε4 carriers among diverse U.S. older adults living at home lose their odor sensitivity well before rapid declines in odor identification and cognition," the authors write. "Future work focused on the neural mechanisms underlying these early manifestations are needed to further understand the effect of APOE allelic variation on both components of olfaction and neurodegeneration."

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