Potential role of vitamin D levels in amyotrophic lateral sclerosis cognitive impairment

Cognitive impairment (CI) is common in amyotrophic lateral sclerosis (ALS): a keystone is identifying factors that could potentially modify the CI course. In recent years, vitamin D is becoming a potential modificatory factor for CI in many neurological disorders. This study aimed to highlight if vitamin D deficiency correlated with CI and clinical features in a cohort of ALS patients. We included 55 ALS patients with a neuropsychological evaluation (classified with the Strong Criteria) and a vitamin D dosage at the diagnosis. We also reviewed medical records and completed data for medical history, physical and neurological examination, and functional scales. At the diagnosis, 30 patients (54%) had CI. Most patients (82%) displayed low vitamin D levels (19.87 ± 9.80 ng/ml). Comparing the vitamin D level between patients with and without CI, we observed significantly lower values in the first group (15.8 ± 8.2 vs. 22.0 ± 9.7 ng/ml, p: 0.04). In the spinal female subgroup (n = 15), we found an inverse correlation between vitamin D and bizarreness score in the cognitive estimates test (r = 0.58; p: 0.04) and a positive correlation with the Corrected Raven’s Standard Progressive Matrices (r = 0.53, p: 0.04). Conversely, in the bulbar female group, we observed a correlation with the corrected direct span (r = 0.84, p: 0.03). With the log-rank survival analysis, we found that the patients with vitamin D < 10 ng/ml had a shorter disease duration (Chi: 5.78, p: 0.02). Our results indicate that levels of vitamin D can influence the cognitive status of people living with ALS and that severe deficits might be an adverse prognostic survival factor.