Page 94 - The autoimmune hypothesis of narcolepsy and its unexplored clinical features M.S. Schinkelshoek

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Chapter 5
led to incomplete data about symptom severity at treatment initiation and made correlation between treatment effects on BMI and treatment effects on other symptoms impossible. We were, however, able to review the medical records of all patients with NT1 patients who had treatment started at the outpatient clinic, thereby reducing the risk of selection bias. Our cohort is also larger than those presented in earlier studies on weight loss and SXB (Donjacour et al., 2013; Husain et al., 2009); and we only included NT1 patients as diagnosed based on ICSD-3 guidelines.
Co-medication constituted a concern in our study. The use of methylphenidate or dexamphetamine was found to be significantly different between groups. Methylphenidate, a stimulant often used in narcolepsy, is known to decrease appetite and dietary fat intake in healthy subjects (Goldfield et al., 2007). In NT1 no such effect has been observed (Kok et al., 2003). It remains unclear whether these findings also lead to a BMI decrease. Given that in our study all patients using these two medications were on a stable dose for at least three months before initiating treatment with SXB or modafinil, it was not likely that this influenced our results in a significant way. We assessed the effect of these stimulants in two ways. Removing individuals using methylphenidate or dexamphetamine from the model still shows a highly significant effect of SXB on BMI. In addition, adding use of dexamphetamine or methylphenidate to the model shows that it leads to a BMI reduction, but does not interfere with the BMI decrease that is demonstrated in the SXB group. Besides stimulants, a non-significant difference in antidepressant use was found between both groups. Results on the effect on BMI of the most frequently used antidepressant clomipramine are contradictory: two groups have reported an increase in appetite and weight gain in patients using clomipramine (Paige et al., 2015; Maina et al., 2004). However, this effect was only shown in patients without narcolepsy and for a higher dose than normally prescribed in NT1. Another group found no BMI changes in narcolepsy patients using clomipramine in patients who were already on a stable dose (Kok et al., 2003).