(P09-039-25) Examination of the Current Evidence on Suboptimal Vitamin B12 Status and Neuropsychiatric Outcomes

Objectives: Vitamin B₁₂ is an important cofactor for DNA synthesis, myelin formation, and neurotransmitter metabolism. Vitamin B₁₂ status has an established link to neurodegeneration and neuropathy, while associations to other neuropsychiatric conditions remain poorly understood. This study aimed to synthesize the evidence examining associations between suboptimal B₁₂ status and neuropsychiatric outcomes using multiple measures of vitamin B₁₂.

Methods: We conducted an umbrella review of systematic reviews (SR) and meta-analyses (MA). Medline, EMBASE, CINHAL, Cochrane Library, Wanfang, and CNKI databases were systematically searched. Screening and data abstraction were performed in duplicate. Methodological quality of each article was assessed using AMSTAR-2. Credibility of evidence was assessed using predefined criteria (convincing, highly suggestive, suggestive, and weak).

Results: A total of 38 syntheses (13 MA, 25 SR) were identified, reporting on 35 associations across 12 unique health outcomes. Most of the included syntheses had medium to low quality and most of the MA comprised of retrospective observational studies. Of the 35 associations, none were assessed to be of convincing or highly suggestive credibility. Two associations were assessed to be of suggestive level of credibility: higher dietary intake of B₁₂ was associated with lower risk of depressive symptoms (RR=0.86 (0.75, 0.99), 3,172 cases, I²=31.3%) and lower serum concentration of total B₁₂ was associated with higher peripheral neuropathy (OR=1.51 (1.23, 1.84), 2,948 cases, I²=43.3%). We noted substantial heterogeneity in exposure/outcome measures, populations, and settings, predominantly retrospective direction of inquiry among the component studies, and varying levels of confounder adjustment across the included studies.

Conclusions: The current evidence on the association of vitamin B₁₂ with neuropsychiatric outcomes was largely limited in terms of volume and quality. Additional research is needed to elucidate associations, if any, between suboptimal B₁₂ status and neuropsychiatric outcomes. Studies with clearly defined exposure thresholds and populations will benefit researchers and public health decision-makers.

Funding Sources: Canadian Institutes for Health Research (FRN-PJT-175263)