Neurology: a meta-analysis of the relationship between mild cognitive impairment or dementia leading to subjective cognitive decline and Alzheimer's disease biomarkers

The risk of mild cognitive impairment or dementia in patients with subjective cognitive decline (SCD) and pathology indicative of Alzheimer's disease (AD) compared to patients with SCD without evidence of AD biomarkers is critical
to characterizing the potential role of biomarkers in this group.
A recent study published in Neurology conducted a meta-analysis
of this topic.

Three databases (PUBMED, PsycINFO and Cochrane) were searched
from inception until May 7, 2021.
The search string includes terms: subjective cognitive decline, biomarkers, amyloid, tau protein, risk, Alzheimer's disease, mild cognitive impairment, and dementia
.
Following PRISMA and Cochrane guidelines, the two researchers independently conducted literature searches, data collection, and data extraction
.
The odds ratio (OR) for random-effects meta-analyses was summarized and sensitivity, specificity, positive and negative predictive values (PPV, NPV) and likelihood ratios
were calculated.
The primary outcome is the chance
of progression from SCD to MCI or dementia in cases with biomarkers indicated by AD pathology relative to those with biomarkers without an indication of AD pathology.

Of the 4147 studies selected, eight studies
were selected.
Risk of bias analysis showed low
risk of bias across all studies.
The prevalence of abnormal biomarkers is 15,6% -35,4% amyloid, 11,1% -33,7% p-tau, 12,4% -46,3% t-tau, 7,8% -24,4% complete AD pathology (amyloid pathology with increased p-tau or t-tau).

Only elevated in amyloid pathology (OR = 5.
89, 95% CI: 2.
33 to 14.
90), elevated p-tau (OR = 3.
99, 95% CI: 2.
34-6.
85), elevated t-tau (OR = 2.
26, 95% CI: 1.
14.
48), and complete AD pathology (OR = 11.
36, 95% CI 1.
97-65.
41).

。 The latter showed PPV of 59.
7% (95% CI: 48.
8% to 69.
3%) and NPV of 89.
4% (95% CI: 86.
7 to 91.
7%), while amyloid pathology showed only PPV of 28.
2% (95% CI: 23.
7% to 32.
2%) and NPV of 94.
9% (95% CI: 93.
4% to 96.
2%)
.

Individuals with SCD and complete AD pathology have a substantially increased
risk of developing MCI or dementia compared with patients with SCD without AD pathology.

Source: Rostamzadeh A, Bohr L, Wagner M, Baethge C, Jessen F.
Progression of Subjective Cognitive Decline to MCI or Dementia in Relation to Biomarkers for Alzheimer Disease: A Meta-Analysis [ published online ahead of print, 2022 Aug 26].
Neurology.
2022; 10.
1212/WNL.
0000000000201072.
doi:10.
1212/WNL.
0000000000201072