Biomarkers

Puipui Malu Manatu is a NIA-funded study of ADRD prevalence, risk factors, and biomarker profiles in American Samoa. We report cognitive and biomarker findings on the first 400 participants. Data collection is ongoing.

A probability sample of 981 Samoan elders age 50+ will be enrolled to (a) study ADRD health literacy, risk and resilience factors, and cognitive screening tools, (b) have a Gold Standard evaluation using the UDSv3.0, and (c) explore genetic and blood-based biomarkers including PrecivityAD2 (C2N Diagnostics).

The cohort had a mean age of 60.4 ± 7.3y, 11.3 ± 2.5y of education, and 58% women. The mean MoCA score was 14.3 ± 3.7 (Range 3-22) and the mean Cognivue Clarity score was 54.8 ± 20.2 (Range 0-90). The mean QDRS score was 1.9 ± 2.4 (Range 0-15.5). The cohort reported 39% subjective cognitive decline, and more than half endorsed mood disturbance. The mean CDR-SB was 0.5 ± 1.0 (Range 0-10) with 69% CDR 0, and 31% CDR 0.5+. Cognitively impaired participants were older, male, had more medical co-morbidities, more subjective complaints, and lower MoCA scores. There were no differences between groups in the UDSv3.0 neuropsychological battery except for verbal fluency. On average, Samoan elders scored >2 SD below normative values on all cognitive tests. ApoE ε3/ε3 was the most genotype (49%) with 33% ApoE ε4 carriers equally distributed between CDR 0 and CDR 0.5+. 19% had low Aβ42/40 ratios and 44% had elevated pTau217% ratios but there were no differences in AD biomarkers between CDR 0 and CDR 0.5+. Aβ42/40 ratio was weakly correlated with vascular risk factors, depression, and cognitive performance, while pTau217% ratios and APS2 scores were moderately correlated with age and CDR-SB scores.

The prevalence of cognitive impairment in American Samoa is 31%. Most cases of cognitive impairment appear not to be related to AD pathology and ApoE ε4 does not appear to be a risk factor. Our study findings suggest that (a) exploration of non-AD biomarkers is needed, (b) cultural tailoring and re-examination of inter-individual normative values for cognitive tests are important, and (c) intra-individual change as measured by the CDR may be a more valid method of dementia detection.