Marc De Buyzere

Universitair Ziekenhuis Ghent, Gand, Flanders, Belgium

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Publications (5)19.25 Total impact

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    ABSTRACT: Stress is a complex phenomenon coordinated by two main neural systems: the hypothalamic-pituitary-adrenal system with cortisol as classical stress biomarker and the autonomic nervous system. For the last system, heart rate variability (HRV) is recently suggested as stress marker. To test low HRV as stress indicator in young children, associations with self-reported chronic stress aspects and salivary cortisol were performed. Therefore, 5-minute HRV data was collected, together with salivary cortisol (4 samples/day, 2 days) (N=293) and stress related questionnaires (negative events, emotions and problems) (N=334) in children (5-10y) of the Belgian ChiBS study. Peer problems, anger, anxiety and sadness were associated with lower root mean square of successive differences (RMSSD) and high frequency power (i.e. lower parasympathetic activity). Anxiety and anger were also related to a higher low frequency to high frequency ratio. Using multilevel modelling, higher cortisol levels, a larger cortisol awakening response and steeper diurnal decline were also associated with these HRV patterns of lower parasympathetic activity. Conclusion: Low HRV (lower parasympathetic activity) might serve as stress indicator in children.
    Biological psychology 09/2013; · 4.36 Impact Factor
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    ABSTRACT: Short sleep duration and poor sleep quality in children have been associated with concentration, problem behavior, and emotional instability, but recently also with disrupted autonomic nervous function, which predicts cardiovascular health. Heart rate variability (HRV) was used as noninvasive indicator of autonomic function to examine the influence of sleep. Cross-sectional and longitudinal observational study on the effect of sleep on HRV. Belgian children (5-11 years) of the ChiBS study in 2010 (N = 334) and 2011 (N = 293). N/A. Sleep duration was reported and in a subgroup sleep quality (efficiency, latency, awakenings) was measured with accelerometry. High-frequency (HF) power and autonomic balance (LF/HF) were calculated on supine 5-minute HRV measurements. Stress was measured by emotion and problem behavior questionnaires. Sleep duration and quality were used as HRV predictors in corrected cross-sectional and longitudinal regressions. Stress was tested as mediator (intermediate pathway) or moderator (interaction) in sleep-HRV associations. In both cross-sectional and longitudinal analyses, long sleep latency could predict lower HF (parasympathetic activity), while nocturnal awakenings, sleep latency, low sleep efficiency, and low corrected sleep duration were related to higher LF/HF (sympathetic/parasympathetic balance). Parental reported sleep duration was not associated with HRV. The significances remained after correction for stress. Stress was not a mediator, but a moderator (enhancer) in the relationship between sleep quality and HRV. Low sleep quality but not parent-reported low sleep duration leads to an unhealthier heart rate variability pattern (sympathetic over parasympathetic dominance). This stresses the importance of good sleep quality for cardiovascular health in children. Michels N; Clays E; De Buyzere M; Vanaelst B; De Henauw S; Sioen I. Children's sleep and autonomic function: low sleep quality has an impact on heart rate variability. SLEEP 2013;36(12):1939-1946.
    Sleep 01/2013; 36(12):1939-46. · 5.10 Impact Factor
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    ABSTRACT: This paper provides age- and sex-specific reference values for short-term heart rate variability (HRV) data in children by time domain and frequency domain methods. Furthermore, HRV determinants will be determined. In 460 children (5-10 years), 5-minute HRV measurements in supine position were undertaken with Polar chest belts. The data were manually edited and processed with time and frequency domain methods. Age, time point, physical activity (accelerometry), physical fitness (cardiopulmonary fitness, upper and lower limb muscular fitness) and body composition (body mass index, fat%, fat and fat-free mass) were analysed as determinants using multiple regression analysis stratified by sex. Sex- and age-specific reference values were produced. Overall, girls had lower HRV. Age-related parasympathetic increases and sympathetic decreases were seen with sometimes age-related year-to-year wave-like changes in boys. The time point of recording had limited influence on HRV. Of the lifestyle related factors, fatness (only 7 % overweight) was not associated with HRV but fat-free mass, physical activity and in particular physical fitness (over and above activity) had a favourable association by increased parasympathetic activity. Future HRV studies in children should consider age, sex and physical fitness.
    Arbeitsphysiologie 12/2012; · 2.66 Impact Factor
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    European journal of human genetics: EJHG 08/2010; 18(8):881. · 3.56 Impact Factor
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    ABSTRACT: Stickler syndrome is an autosomal dominant connective tissue disorder caused by mutations in different collagen genes. The aim of our study was to define more precisely the phenotype and genotype of Stickler syndrome type 1 by investigating a large series of patients with a heterozygous mutation in COL2A1. In 188 probands with the clinical diagnosis of Stickler syndrome, the COL2A1 gene was analyzed by either a mutation scanning technique or bidirectional fluorescent DNA sequencing. The effect of splice site alterations was investigated by analyzing mRNA. Multiplex ligation-dependent amplification analysis was used for the detection of intragenic deletions. We identified 77 different COL2A1 mutations in 100 affected individuals. Analysis of the splice site mutations showed unusual RNA isoforms, most of which contained a premature stop codon. Vitreous anomalies and retinal detachments were found more frequently in patients with a COL2A1 mutation compared with the mutation-negative group (P<0.01). Overall, 20 of 23 sporadic patients with a COL2A1 mutation had either a cleft palate or retinal detachment with vitreous anomalies. The presence of vitreous anomalies, retinal tears or detachments, cleft palate and a positive family history were shown to be good indicators for a COL2A1 defect. In conclusion, we confirm that Stickler syndrome type 1 is predominantly caused by loss-of-function mutations in the COL2A1 gene as >90% of the mutations were predicted to result in nonsense-mediated decay. On the basis of binary regression analysis, we developed a scoring system that may be useful when evaluating patients with Stickler syndrome.
    European journal of human genetics: EJHG 02/2010; 18(8):872-80. · 3.56 Impact Factor