Interactions between apolipoprotein E and apolipoprotein(a) in patients with late-onset Alzheimer disease.

BACKGROUND

Apolipoprotein(a) [apo(a)], the distinctive, highly polymorphic glycoprotein of lipoprotein(a), shares a series of common features with apolipoprotein E (apoE), which is implicated in the development of Alzheimer disease.

OBJECTIVE

To determine whether apo(a) is associated with Alzheimer disease.

DESIGN

Case-control study.

SETTING

University hospitals in Europe.

PARTICIPANTS

285 patients with Alzheimer disease and 296 controls.

MEASUREMENTS: Plasma lipoprotein(a) levels, size of the apo(a) isoforms, and apoE and apo(a) genotyping.

RESULTS

Among carriers of the apoE epsilon4 allele, lipoprotein(a) was associated with a progressive, age-dependent increased risk for late-onset Alzheimer disease (odds ratio for patients >80 years of age, 6.0 [95% CI, 1.2 to 30.8]; P<0.01). Among noncarriers older than 80 years of age, lipoprotein(a) was associated with a reduced risk for Alzheimer disease (odds ratio, 0.4 [CI, 0.2 to 0.91; P<0.05).

CONCLUSIONS

In this convenience sample, lipoprotein(a) was an additional risk factor for late-onset Alzheimer disease in carriers of the apoE epsilon4 allele. However, lipoprotein(a) may protect against late-onset Alzheimer disease in noncarriers.