Background: Chronotype reflects an individual's optimal daily timing of sleep, activity, and cognitive performance. Previous, cross-sectional, studies have suggested an age effect on chronotype... Show moreBackground: Chronotype reflects an individual's optimal daily timing of sleep, activity, and cognitive performance. Previous, cross-sectional, studies have suggested an age effect on chronotype with later chronotypes in adolescents and earlier chronotypes in children and elderly. Additionally, later chronotypes have been associated with more depressive symptoms. Few studies have been able to study longitudinal associations between chronotype and age, while adjusting for depressive symptoms. Methods: Chronotype was assessed twice with the Munich Chronotype Questionnaire 7 years apart in the Netherlands Study of Depression and Anxiety (T1: N = 1842, mean age (SD): 42.63 years (12.66)) and T2: N = 1829, mean age (SD) 50.67 (13.11)). The longitudinal association between change in age and change in chronotype was tested using a generalized estimated equation analysis adjusted for covariates (including level of depressive symptoms). Using age-bins of 5 years (age at T2), change in chronotype between T1 and T2 was analyzed with Linear Mixed Models. Results: We found a change towards an earlier chronotype with higher age (B (95% CI): -0.011 (-0.014-0.008), p < 0.001). For the age-bins, the difference in chronotype was significant for the 25-29 years age-bin. Limitations: The sample did not include individuals younger than 19 years or older than 68 years. Conclusions: In the whole sample chronotype changed towards becoming more morning-type over a period of 7 years, but this change was only significant for those aged 25-29 years. The study was performed in a large naturalistic cohort study with a wide age-range, including patients with a diagnosis of depressive and anxiety disorder and healthy controls. Show less
Objectives Rheumatoid arthritis (RA) patients show an earlier circadian rhythm (i.e. serum melatonin peaks earlier during the night, indicating an earlier timing of the internal circadian pacemaker... Show moreObjectives Rheumatoid arthritis (RA) patients show an earlier circadian rhythm (i.e. serum melatonin peaks earlier during the night, indicating an earlier timing of the internal circadian pacemaker). In the current study, we examined whether the chronotype, which is influenced by the circadian rhythm, is also earlier. In addition, we explored whether chronotype is related to disease activity and patient-reported outcomes.Methods The chronotype (Munich Chronotype Questionnaire) of patients with RA (n = 121; mean age 60 years, 73% female) was compared with that of subjects from the general population (norm group; n = 1695) with a one-sample t test. In addition, we investigated chronotype in relation to disease activity (Disease Activity Score; DAS), reported morning stiffness, fatigue (Checklist Individual Strength), and health-related quality of life (RAND-36).Results The chronotype of patients with RA was, on average, 23 min (95% CI, 15 to 31 min) earlier than that of the norm group (t(115) = - 5.901, p < 0.001, d = 0.55). Chronotype was not related to disease activity or patient-reported outcomes (p > 0.05).Conclusion As expected, chronotype was earlier in RA patients. However, in this correlational study, chronotype was not related to disease activity or patient-reported outcomes. An experimental study is needed to examine whether delaying the circadian rhythm has a positive influence on these outcomes. This insight could improve our understanding of the pathophysiology of RA and contribute to exploring new treatment possibilities.Key Points This is the first study examining chronotype in patients with rheumatoid arthritis, and how chronotype relates to disease activity and patient-reported outcomes.We found an earlier chronotype in patients with rheumatoid arthritis than in subjects from the general population.In this correlational study, chronotype was not related to disease activity or patient-reported outcomes. An experimental study is needed to examine whether delaying the circadian rhythm positively influences these outcomes. Show less
The premonitory phase and early phase of both spontaneous and nitroglycerin-triggered migraine attacks were explored in this thesis, in association with clinical modulators and trigger factors.... Show moreThe premonitory phase and early phase of both spontaneous and nitroglycerin-triggered migraine attacks were explored in this thesis, in association with clinical modulators and trigger factors. Clinical research strategies, experimental designs, neuroimaging techniques and biochemical methods have revealed clinical risk factors, biochemical modulators and pharmacological triggers. Furthermore, newly discovered hypothalamus-specific alterations in metabolism and perfusion in the early phases of the migraine attack were described. Taken together, these results suggest that each migraine attack starts well before the initiation of the headache phase. The hypothalamus is postulated to have a pivotal role in the early phases of the migraine attack, and possibly affects attack susceptibility interictally as well. Show less
Background: The role of chronotype, the individual timing of sleep/activity, has been studied in relation todepressive and anxiety disorders. A cross-sectional association between a depressive... Show moreBackground: The role of chronotype, the individual timing of sleep/activity, has been studied in relation todepressive and anxiety disorders. A cross-sectional association between a depressive episode and evening-typehas been identified. However, until now the predicting capacity of chronotype concerning persistence of psy-chiatric disorders remains unclear. Our aim is to examine whether a later chronotype in patients with a de-pressive and/or anxiety disorder can serve as a predictor of a persistent course.Methods: A subsample of patients with a depressive and/or anxiety disorder diagnosis and chronotype data ofthe longitudinal Netherlands Study of Depression and Anxiety (NESDA) was used. Diagnosis of depressive andanxiety disorders (1-month DSM-IV based diagnosis) were determined at baseline (n = 505). From this grouppersistence was determined at 2-year (FU2) (persistent course: n = 248, non-persistent course: n = 208) and 4-year follow-up (FU4) (persistent course: n = 151, non-persistent course: n = 264). Chronotype was assessed atbaseline with the Munich Chronotype Questionnaire.Results: A later chronotype did not predict a persistent course of depressive and/or anxiety disorder at FU2 (OR(95% CI) = 0.99 (0.83–1.19), P = 0.92) or at FU4 (OR (95% CI) = 0.94 (0.77–1.15), P = 0.57).Limitations: Persistence was defined as having a diagnosis of depressive and/or anxiety disorder at the two-yearand four-year follow-up, patients may have remitted and relapsed between assessments.Conclusion: Chronotype, measured as actual sleep timing, of patients with a depressive or anxiety disorder didnot predict a persistent course which suggests it might be unsuitable as predictive tool in clinical settings. Show less
Sleep problems are highly prevalent in ADHD and autism spectrum disorder (ASD). Better insight in the etiology is of clinical importance since intervention and prevention strategies of sleep... Show moreSleep problems are highly prevalent in ADHD and autism spectrum disorder (ASD). Better insight in the etiology is of clinical importance since intervention and prevention strategies of sleep problems are directed at underlying mechanisms. We evaluated the association of sleep problems and sleep patterns with sleep hygiene (behavioral/environmental practices that influence sleep quality, e.g. caffeine use), access to electronic media, chronotype, and anxiety/depression in children aged 6–12 years with ADHD, ASD, or typical development (TD) using parental questionnaires. ANOVA and linear regression analyses were adjusted for age and sex. Children with ADHD and ASD showed more sleep problems (63.6 and 64.7%, vs 25.1% in TD) and shorter sleep duration than controls, while differences between ADHD and ASD were not significant. Sleep hygiene was worse in ADHD and ASD compared to TD, however, the association of worse sleep hygiene with more sleep problems was only significant in ASD and TD. There was a significant association of access to electronic media with sleep problems only in typically developing controls. Chronotype did not differ significantly between groups, but evening types were associated with sleep problems in ADHD and TD. Associations of greater anxiety/depression with more sleep problems were shown in ADHD and TD; however, anxiety/depression did not moderate the effects of chronotype and sleep hygiene. We conclude that sleep problems are highly prevalent in ADHD and ASD, but are differentially related to chronotype and sleep hygiene. In ASD, sleep problems are related to inadequate sleep hygiene and in ADHD to evening chronotype, while in TD both factors are important. Clinical implications are discussed. Show less
In modern society, circadian rhythms and sleep are often disturbed, which may negatively affect health. This thesis examines these associations and focuses on the basic functioning of sleep and the... Show moreIn modern society, circadian rhythms and sleep are often disturbed, which may negatively affect health. This thesis examines these associations and focuses on the basic functioning of sleep and the circadian system in mice and in humans. Circadian rhythms are orchestrated by ~20,000 neurons in the central clock in the suprachiasmatic nuclei (SCN) in the brain. In mice, a complete abolishment of central clock-driven rhythms resulted in obesity and severe hepatic insulin resistance. An attenuation of rhythms resulted in decreased muscle strength, osteoporosis-like bone changes and transient changes in the immune system. In humans, short sleeping obese individuals with a preference for evening activities ("evening chronotypes") had increased cardiovascular risk factors. Their neurocognitive function was often impaired and could be improved with sleep extension. Insufficient sleep was also associated with an increased risk for osteopenia and sarcopenia. Taken together, disrupted circadian rhythms and insufficient sleep associate with a spectrum of unfavorable health outcomes. Studies described in the thesis provide insight in potential strategies to improve rhythms and sleep: by appropriately timed behavior (active behavior during the active phase; rest during the rest phase), light exposure (light during the subjective day; darkness at night) as well as caffeine intake. Show less
