Purpose: To identify prevalence and associated factors of cognitive dysfunction in opioid-treated patients with cancer.
Patients and methods: EPOS (European Pharmacogenetic Opioid Study) is a prospective cross-sectional multicenter study in which adult patients with cancer who received treatment with opioids for moderate or severe pain for at least 3 days were included. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). MMSE scores were categorized into definite cognitive dysfunction (scores < 24), possible cognitive dysfunction (scores 24-26), and no cognitive dysfunction (scores > 26). Factors potentially associated with cognitive dysfunction were assessed. Associations between MMSE and explanatory variables were analyzed by ordinal logistic regression models.
Results: We included 1,915 patients with cancer from 17 centers. MMSE scores less than 27 were observed in 32.9% of patients. Patients with lung cancer had higher odds (adjusted odds ratio, 1.46; 95% CI, 1.09 to 1.95) for having lower MMSE scores compared with patients with other cancer diagnoses. Patients receiving daily opioid doses of 400 mg or more (oral morphine equivalents) had 1.75 (95% CI, 1.25 to 2.46) times higher odds of having lower MMSE scores compared with those receiving daily doses less than 80 mg. Other risk factors for cognitive dysfunction were older age, low Karnofsky performance status (KPS), time since diagnosis (< 15 months), and absence of breakthrough pain (BTP).
Conclusion: One third of opioid-treated patients with cancer had possible or definite cognitive dysfunction. Lung cancer, daily opioid doses of 400 mg or more (oral morphine equivalents), older age, low KPS, shorter time since cancer diagnosis, and absence of BTP were predictors for cognitive dysfunction.