Page 92 - The autoimmune hypothesis of narcolepsy and its unexplored clinical features M.S. Schinkelshoek

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Chapter 5
or methylphenidate use was significant (F(1,78.787) = 10.215, p = 0.002). However, there still remained a highly significant main effect of SXB on BMI (F(1,66.799) = 14.916, p < 0.001).
Discussion
Our findings (1) confirm that SXB reduces BMI in NT1 patients and (2) suggest that this is a long lasting effect. Even when accounting for baseline BMI, gender, treatment duration and the interactions between them, the mixed model we fitted statistically significantly demonstrates a BMI decrease in the SXB group, in contrast to a BMI increase in the modafinil group. The BMI decrease in the SXB group is seen in both males and females but is more pronounced in women. Patients using modafinil gain rather than lose weight. Another interesting finding is that a higher BMI at baseline predicts a more pronounced decrease in BMI during medication use over time. This suggests that BMI decrease constitutes an additional beneficial effect of SXB for NT1 patients, especially for those with a higher BMI at baseline. A correlation between medication dose and BMI change is not found in our cohort.
Our findings are in line with a previous report (Husain et al., 2009) on weight loss amongst patients treated with SXB. Patients with NT1 and -2 were assessed, yet without a control group; and data on age, gender or BMI of the smaller cohort were lacking.
Narcolepsy patients have a higher prevalence of obesity than the general population. Indeed, the mean baseline BMI of our cohort was significantly higher than that of a representative sample of Dutch people older than 18 years old.
The exact mechanism by which SXB leads to weight loss is unclear, though several theories exist. It is known (Donjacour et al., 2011) that SXB leads to a consistent increase in nocturnal growth hormone (GH) secretion and that SXB strengthens the temporal relation between GH secretion and slow wave sleep. GH is a potent lipolytic agent and a GH deficiency decreases lean body mass while increasing fat mass. It was suggested that SXB could lead to an increase in lipolysis by restoring GH secretion. This hypothesis was tested in a study showing that SXB stimulates lipolysis in NT1 (Donjacour et al.,