Body mass index-independent metabolic alterations in narcolepsy with cataplexy.

STUDY OBJECTIVES

To contribute to the anthropometric and metabolic phenotyping of orexin-A-deficient narcoleptic patients, and to explore a possible risk of their developing a metabolic syndrome.

DESIGN

We performed a cross-sectional study comparing metabolic alterations in patients with narcolepsy with cataplexy (NC) and patients with idiopathic hypersomnia without long sleep time.

SETTING

University hospital.

PATIENTS

Fourteen patients with narcolepsy with cataplexy and 14 sex and age-matched patients with idiopathic hypersomnia without long sleep time.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Metabolic parameters were evaluated by measuring body mass index (BMI), waist circumference (also with abdominal computed tomography), blood pressure, and daily calorie intake (3-day diary). Chronotypes were assessed through the morningness-eveningness questionnaire. Lumbar puncture for cerebrospinal fluid orexin-A determination and HLA typing were performed. Patients with narcolepsy with cataplexy (all HLA DQB1*0602 positive and with cerebrospinal fluid orexin-A levels < 110 pg/mL) had a higher BMI and BMI-independent metabolic alterations, namely waist circumference, high-density lipoprotein cholesterol, and glucose/insulin ratio (an insulin resistance index), with respect to patients with idiopathic hypersomnia without long sleep time (cerebrospinal fluid orexin-A levels > 300 pg/mL). Despite lower daily food intake, patients with narcolepsy with cataplexy displayed significant alterations in metabolic parameters resulting in a diagnosis of metabolic syndrome in more than half the cases.

CONCLUSIONS

BMI-independent metabolic alterations and the relative hypophagia of patients with narcolepsy with cataplexy, as compared with patients with idiopathic hypersomnia without long sleep time, suggest that orexin-A influences the etiology of this phenotype. Moreover, considering that these dysmetabolic alterations are present from a young age, a careful metabolic follow-up of patients diagnosed with narcolepsy with cataplexy is mandatory.