Prevalence of Functional Vitamin B12 Deficiency in Elderly Patients with Symptoms of Cognitive Impairment: A Retrospective Study

Abstract Background: Vitamin B12 is necessary for DNA synthesis and supports healthy blood and nerve function. Serum vitamin B12 is a common marker for B12 status, but its levels may not always indicate deficiency. It lacks sensitivity and specificity. Functional vitamin B12 deficiency, marked by elevated methylmalonic acid (MMA) and homocysteine, affects 10% to 30% of people over 65 years. Those markers improve diagnostic accuracy but have disadvantages, including high cost, limited access, and variability in patients with renal impairment. Objectives: To assess vitamin B12 deficiency rates among dementia patients and to examine functional B12 deficiency by evaluating elevated MMA levels in patients with normal circulating B12. Design: A retrospective observational cross-sectional study. Setting: Data collected from elderly patients who visited Dr. Sulaiman Al-Habib Hospital outpatient clinics in the duration between 2015 and 2024. Methods: Eligible participants were randomly selected from the Hospital Information System (HIS) following Institutional Review Board (IRB) ethical approval number (RC 24.11.88). The study cohort comprised 253 elderly individuals presenting with cognitive impairment. Available laboratory data, including serum vitamin B12, MMA, and, if available, homocysteine levels, were used. Statistical analysis was conducted using Statistical Package for the Social Sciences (SPSS) 27 th edition. Categorical variables were presented as counts and percentages, while continuous variables were presented as means, standard deviations, medians, and 25 th and 75 th percentiles. A multivariable logistic regression model was constructed to identify independent predictors of vitamin B12 deficiency among the study participants. A two-tailed P value < 0.05 was considered statistically significant. Results: All participants (100%, n = 253) reported neurological symptoms. B12 deficiency was identified in 41.9% of the cases ( n = 106). An elevated MMA level, a highly specific indicator of functional B12 deficiency, was markedly more prevalent in the deficient group (62.9% vs. 41.8%, P < 0.001). MMA was also a strong and statistically significant predictor of B12 deficiency ( B = 1.004, P = 0.001) with an odds ratio of 2.73 (95% CI: 1.53–4.88). Conclusion: Vitamin B12 deficiency is significantly prevalent in elderly patients (>60 years) with cognitive symptoms (e.g. delirium, forgetfulness). Assessment of functional B12 deficiency by evaluating elevated MMA levels in patients with normal circulating B12 is significant.