Adult narcoleptic patients have increased risk of cancer: A nationwide population-based study

Background: The comorbidity profile, especially cancer risk, of narcoleptic patients has seldom been explored. We used a nationwide database to evaluate the risk of cancer among adult narcoleptic patients. Methods: We conducted the cohort study using National Health Insurance Research Database from 2000 to 2009. Standardized incidence ratios (SIRs) of cancers were calculated to compare the cancer incidence of the study cohort with that of the general population. Results: 2833 narcoleptic patients were identified after excluding patients with antecedent malignancy and age younger than 18 years old. The study cohort was observed for 15,913 person-years during a 10-year period. The median follow-up interval was 5.6 ± 3.0 years. Seventy-four cancers occurred in during the follow-up. The risk of all cancers was found significantly increased in adult narcoleptic patients (SIR 1.32; 95% CI, 1.04-1.66, p=0.0248). Regarding sex, the overall cancer risk was increased in female patients (SIR 1.52; 95% CI, 1.05-2.13, p=0.026). Furthermore, females were found to have more head and neck cancers (SIR 6.17; 95% CI, 1.66-15.80, p=0.009) and gastric cancers (SIR 4.87; 95% CI, 1.31-12.48, p=0.02). For males, the incidence of overall and specific cancer types was not significantly increased. Conclusions: Adult narcoleptic patients had a higher risk for cancer. Further research is warranted to elucidate the mechanism underlying its association.