Efficacy and Blood Plasmalogen Changes by Oral Administration of Plasmalogen in Patients with Mild Alzheimer's Disease and Mild Cognitive Impairment: A Multicenter, Randomized, Double-blind, Placebo-controlled Trial

Background: Plasmalogens (Pls) reportedly decreased in postmortem brain and in the blood of patients with Alzheimer's disease (AD). Recently we showed that intraperitoneal administration of Pls improved cognitive function in experimental animals. In the present trial, we tested the efficacy of oral administration of scallop-derived purified Pls with respect to cognitive function and blood Pls changes in patients with mild AD and mild cognitive impairment (MCI).

Methods: The study was a multicenter, randomized, double-blind, placebo-controlled trial of 24weeks. Participants were 328 patients aged 60 to 85years who had 20 to 27 points in Mini Mental State Examination-Japanese (MMSE-J) score and five or less points in Geriatric Depression Scale-Short Version-Japanese (GDS-S-J). They were randomized to receive either 1mg/day of Pls purified from scallop or placebo. The patients and study physicians were masked to the assignment. The primary outcome was MMSE-J. The secondary outcomes included Wechsler Memory Scale-Revised (WMS-R), GDS-S-J and concentration of phosphatidyl ethanolamine plasmalogens (PlsPE) in erythrocyte membrane and plasma. This trial is registered with the University Hospital Medical Information Network, number UMIN000014945.

Findings: Of 328 patients enrolled, 276 patients completed the trial (140 in the treatment group and 136 in the placebo group). In an intention-to-treat analysis including both mild AD (20≤MMSE-J≤23) and MCI (24≤MMSE-J≤27), no significant difference was shown between the treatment and placebo groups in the primary and secondary outcomes, with no severe adverse events in either group. In mild AD patients, WMS-R improved significantly in the treatment group, and the between group difference was nearly significant (P=0.067). In a subgroup analysis of mild AD patients, WMS-R significantly improved among females and those aged below 77years in the treatment group, and the between-group differences were statistically significant in females (P=0.017) and in those aged below 77years (P=0.029). Patients with mild AD showed a significantly greater decrease in plasma PlsPE in the placebo group than in the treatment group.

Interpretation: Oral administration of scallop-derived purified Pls may improve cognitive functions of mild AD.

Funding: The Japanese Plasmalogen Society.