96 Chapter 4 before hypersomnolence disorder worsening were spontaneously reported by the subject and stricter rules for inclusion therefore applied. Other life events and/or progression of the hypersomnolence disorder were not included in the statistical analyses and only described if the event occurred within one month of the change in the hypersomnolence disorder. The Medical Ethical Committee of the VU Medical Center scrutinized the study. It consisted of an analysis of previously acquired clinical data posing no risk to people, so the study was exempted from the need to obtain individual consent. The clinical experiments conformed to the principals outlined by the Declaration of Helsinki. We followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement for cross-sectional studies guidelines [188]. Diagnostic groups Hypersomnolence diagnoses had to comply with ICSD-3 criteria [8]. Individuals included were classified as having narcolepsy type 1 or 2, or idiopathic hypersomnia. Those with a clear complaint of EDS but without fulfilling ICSD-3 diagnostic criteria were included as people with a “clinical diagnosis”. Appendix A shows an overview of the clinical diagnosis groups’ definitions and the implemented outcome measures. We repeated the analyses without the people with a clinical diagnosis in Appendix B to investigate whether this group had substantially influenced our results. Data processing Immunological event histories of people with narcolepsy type 1 were compared with a combined group of people with narcolepsy type 2 and idiopathic hypersomnia. Tree structures were built on infection and influenza vaccination history for both groups. Each tree consisted of three branches of leaves, each consecutively representing smaller subgroups of the full sample. The number of people were reported per leaf together with their HLA-DQB1*0602 statuses. Individuals were first branched based on whether they reported infection or influenza vaccination before developing their hypersomnolence disorder (first leaf). People in whom an infection and influenza vaccination were reported were included in the event group closest to their hypersomnolence onset. When both events were equally close to hypersomnolence onset, this individual was included in both analyses on infections and influenza vaccinations. The group with a reported infection was then subdivided into flu, EBV, other respiratory, and other non-respiratory infections (second leaf). For vaccination history the group was split into H1N1 influenza vaccination (in 2009–2010) and other types
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