Introduction:
Vitamin B₁₂ deficiency is becoming a major problem among geriatric population worldwide. It may contribute to higher prevalence of cognitive impairment and depression, and may occur as a side effect of commonly prescribed anti-diabetic and anti-acid treatments. However, the scale of this phenomenon in Poland remains unknown.

Aim:
We investigated the scale of vitamin B₁₂ deficiency across population of geriatric patients over 70 years old. Additionally, we examined the association between vitamin B₁₂ deficiency, cognitive impairment or depression prevalence, and metformin or proton pump inhibitors intake.

Material and methods:
Based on the measured vitamin B₁₂ serum level, we divided patients into 3 groups: (1) normal (≥300 pg/mL); (2) borderline (191–300 pg/mL), and (3) low (≤191 pg/mL). The assessment of cognitive impairment or depression was performed by using 5 distinct tests (mini-mental state examination, abbreviated mental test score, clock drawing test, and 4-item or 15-item geriatric depression scale). For statistical analysis, we used χ² and ANOVA tests.

Results and discussion:
We showed no differences in the frequency of cognitive impairment, depression, and vitamin among characterized groups. Importantly, we found that metformin intake was associated with vitamin B₁₂ deficiency (P = 0.009), contrary to proton pump inhibitor (P = 0.53) and combined these drugs (P = 0.24).

Conclusions:
We showed a relatively high prevalence of vitamin B₁₂ deficiency across a population of geriatric patients. A preventive vitamin B₁₂ supplementation should be considered when treating, especially geriatric diabetic patients. Due to conflicting results of retrospective studies, prospective clinical trial should be undertaken to describe the association between vitamin B₁₂ deficiency and prevalence of cognitive impairment or depression.