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Delirium is a common problem among the elderly. The incidence of delirium will increase considerably in the coming decades as the proportion of the population over age 65 increases. Given that an FDA-approved drug to treat delirium is not available, efforts geared toward prevention are paramount. Several risk factors that predispose/precipitate delirium have been identified. A recently described, reversible risk factor for postoperative delirium is obstructive sleep apnea (OSA). In this review, we focus on the molecular basis of delirium and its link to OSA. We present evidence that OSA modulates the levels of two factors, IGF-1 and cortisol, which both have been linked to postoperative delirium.

Evidence is mixed for an association between serum insulin-like growth factor-I (IGF-I) levels and postoperative delirium (POD). The current study assessed preoperative serum IGF-I levels as a predictor of incident delirium in non-demented elderly elective knee arthroplasty patients. Preoperative serum levels of total IGF-I were measured using a commercially available Human IGF-I ELISA kit. POD incidence and severity were determined using DSM-IV criteria and the Delirium Rating Scale-Revised-98 (DRS-R98), respectively. Median IGF-I levels in delirious (62.6 ng/ml) and non-delirious groups (65.9 ng/ml) were not significantly different (p = 0.141). The ratio (95% CI) of geometric means, D/ND, was 0.86 (0.70, 1.06). The Hodges-Lehmann median difference estimate was 7.23 ng/mL with 95% confidence interval (−2.32, 19.9). In multivariate logistic regression analysis IGF-I level was not a significant predictor of incident POD after correcting for medical comorbidities. IGF-I levels did not correlate with DRS-R98 scores for delirium severity. In conclusion, we report no evidence of association between serum IGF-I levels and incidence of POD, although the sample size was inadequate for a conclusive study. Further efforts to investigate IGF-I as a delirium risk factor in elderly should address comorbidities and confounders that influence IGF-I levels.