Association of preoperative vitamin D deficiency with the risk of postoperative delirium and cognitive dysfunction: A meta-analysis

Despite vitamin D deficiency (VDD) associated with cognitive dysfunction in the general population, the impacts of preoperative VDD on postoperative delirium (POD) and cognitive dysfunction (POCD) remain to be clarified. Meta-analysis of cohort studies. Postoperative care. Preoperative VDD as the prognostic factor. Adult patients undergoing surgery. Databases including MEDLINE, EMBASE, Google scholar, and the Cochrane Library databases were searched from inception to September 2021. Random-effects modeling was applied to the pooling of results on the association between preoperative VDD and POD/POCD. The primary outcome was the association of VDD with the risk of POD/POCD, while the secondary outcomes included other prognostic factors (e.g., hypertension) with the risk of POD/POCD. A prediction interval (PI) was calculated to indicate the range of a true effect size of a future study in 95% of all populations. Meta-analysis of seven observational studies involving 2673 patients showed that the pooled incidence of POD/POCD was 29% (95% confidence interval (CI): 18% to 44%). Our results demonstrated that preoperative VDD increased the risk of POD/POCD [odds ratio (OR) = 1.54, 95% CI: 1.21–1.97, p < 0.01; I2 = 29.2%, seven studies, 2673 patients; 95% PI: 0.89–2.67], while vitamin D insufficiency was not associated with a higher risk of POD/POCD (OR = 0.88, 95% CI: 0.49–1.57, p = 0.66; I2 = 62.6%, four studies, 1410 patients; 95% PI: 0.09–8.79). The PI in our primary outcome (i.e., 0.89 to 2.67) containing 1.0 suggested the possibility of inconsistent results in future studies. Patients with POD/POCD were older compared to those without. Hypertension, diabetes mellitus, male gender, or smoking was not recognized as risk factors for POD/POCD. Our results demonstrated that preoperative vitamin D deficiency was associated with postoperative cognitive impairment. Given the prediction interval, more future studies are needed to elucidate associations between VDD and POD/POCD.