Investigation of the effects of serum phosphate level on cognitive functions in individuals aged over 65

Serum phosphate, a parameter modifiable through dietary or pharmacological interventions, has been associated not only with vascular impairment but also with neurological disorders, yet evidence regarding its effects on cognitive function is limited. This study aimed to investigate the relationship between serum phosphate levels and cognitive performance in individuals aged 65 years and older. A total of 258 participants who applied to the Geriatrics Department of Ankara Bilkent City Hospital were included according to exclusion criteria. Serum phosphate levels, Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and Mini Nutritional Assessment–Short Form (MNA-SF) scores were obtained from digital medical records, and cognitive functions were further assessed with a computer-based test battery. In the first stage, correlation analysis was performed; in the second stage, serum phosphate levels were categorized as <2.50 (group 1), 2.50–3.49 (group 2), 3.50–3.99 (group 3), and ≥4.00 mg/dL (group 4), and intergroup comparisons were conducted. A weak positive correlation was found between phosphate levels and MMSE scores (p < 0.05). MMSE scores were significantly lower in group 1, while MoCA scores were significantly reduced in both groups 1 and 4 (p < 0.05). No significant differences were observed among groups in MNA-SF (p > 0.05). Regarding computer-based tests, no differences were found in PVT, B-GRZ, and K-GRZ, whereas the longest reaction times in BT-GRZ and KT-GRZ were identified in group 1 (p < 0.05). Monitoring serum phosphate may serve as a useful biomarker for the early detection and prevention of cognitive decline in older adults. By focusing solely on phosphate and excluding other risk factors, this study demonstrated that even mild deviations can negatively affect cognition, while the computer-based test battery showed high specificity in detecting impairment and appears promising for clinical application. Future studies stratifying older adults into narrower age groups may provide more detailed insights.