Marc De Buyzere

Ghent University, Gand, Flemish, Belgium

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Publications (11)51.82 Total impact

  • Hypertension 11/2014; 65(1). DOI:10.1161/HYPERTENSIONAHA.114.04619 · 7.63 Impact Factor
  • Hypertension 09/2014; 64(6). DOI:10.1161/HYPERTENSIONAHA.114.04497 · 7.63 Impact Factor
  • Hypertension 08/2014; 64(4). DOI:10.1161/HYPERTENSIONAHA.114.04401 · 7.63 Impact Factor
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    ABSTRACT: Objectives: 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. Design: Cross-sectional and longitudinal observational study on the effect of sleep on HRV Participants: Belgian children (5-11 years) of the ChiBS study in 2010 (N = 334) and 2011 (N = 293). Interventions: N/A. Methods: Sleep duration was reported and in a subgroup sleep quality (efficiency, latency, awakenings) was measured with accelerometry. Highfrequency (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. Results: 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. Conclusions: 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.
    Sleep 12/2013; 36(12):1939-46. DOI:10.5665/sleep.3234 · 5.06 Impact Factor
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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; DOI:10.1016/j.biopsycho.2013.08.005 · 3.47 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; 113(6). DOI:10.1007/s00421-012-2572-9 · 2.30 Impact Factor
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    ABSTRACT: Oral presentation at the 42nd ISPNE annual conference in New York; September 2012. Rationale/statement of the problem: Stress is a complex phenomenon coordinated by several neural systems and has consequently been measured by several biomarkers. Salivary cortisol is the classical used stress biomarker representing the hypothalamic-pituitary-adrenal system. Heart rate variability (HRV), defined as the distance variability between consecutive R peaks, is increasingly used as marker of the autonomic nervous system and as a result also as a stress marker (defined as sympathetic over parasympathetic dominance). Associations between children's salivary cortisol and HRV will be examined. Methods: In 190 children (5–10 year) of the Belgian ChiBS study salivary cortisol and HRV were sampled. Salivary cortisol samples were collected when waking up, 30 minutes and 60 minutes after wake-up and in the evening on two weekdays. HRV measurements in supine position were undertaken with Polar chest belts during 5 minutes. Apart from HRV time-domain analysis, also frequency-domain analysis was performed in the low-frequency (LF) and high-frequency (HF) bands. Multilevel growth curve modelling with adjustments for age, sex, physical activity and wake-up time was used to analyse the HRV associations with overall cortisol, cortisol awakening response (CAR) and cortisol diurnal decline. Results: Higher overall cortisol levels were negatively associated with mean RR, root mean square of successive differences (RMSSD), percentage of RR intervals differing more than 5 0ms (pNN50) and HF. A steeper diurnal decline was positively associated with normalised LF and the LF/HF ratio and negatively with HF. The CAR was positively associated with normalised LF and the LF/HF ratio and negatively with normalised HF. Conclusion: Higher salivary cortisol levels were associated with lower parasympathetic activity. A larger CAR and steeper diurnal decline were associated with a sympathetic over parasympathetic dominance. Consequently, the two main neural stress systems (represented by cortisol and HRV) show good agreement in reflecting children's stress status, although not all parameters were significantly related. Measuring both pathways stays recommended as the pathways might be stimulated differently depending on the stressor. Related publications: Michels N, Sioen I, Clays E, De Buyzere M, Ahrens W, Huybrechts I, Vanaelst B, De Henauw S, 2013. Children’s heart rate variability as stress indicator: association with stress questionnaires and salivary cortisol. Biological Psychology, 94(2): 433-40. Michels N, Sioen I, Huybrechts I, Bammann K, Vanaelst B, De Vriendt T, Iacoviello L, Konstabel K, Ahrens W, De Henauw S, 2012. Negative life events, emotions and psychological difficulties as determinants of salivary cortisol in Belgian primary school children. Psychoneuroendocrinology, 37(9): 1506-15. IF=5.8, rank: 16/135
    09/2012; 3. DOI:10.3402/ejpt.v3i0.19444
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    ABSTRACT: The risk of pulmonary vein narrowing (PVN) after pulmonary vein isolation, using a novel multi-electrode ablation catheter, is unknown. Left atrial volume and PV diameters were compared by computed tomography (CT) before and 3 months after pulmonary vein isolation using duty-cycled phased radio frequency energy (2:1 or 4:1 bipolar/unipolar ratio) in 50 patients. Pulmonary vein diameter was measured in a coronal and axial view at 3 levels (A, ostium; B, 1 cm more distal; C, 2 cm more distal). Moderate PVN was defined as a pulmonary vein diameter reduction of 25 to 50%, and severe PVN as >50%. Left atrial volume decreased by 12±12% (P<0.01). Axial pulmonary vein diameter shortened by a median of 16% (interquartile range [IQR] 28 to 5%), 13% (IQR 25 to 5%), and 9% (IQR 21 to -3%) at level A, B, and C, respectively (P<0.01 for all); coronal pulmonary vein diameter decreased by a median of 16% (IQR 24 to 7%), 11% (IQR 21 to 4%), and 8% (IQR 18 to -2%; P<0.01 for all). Moderate PVN occurred in 30% of the PVs, in 78% of the patients; severe PVN occurred in 4% of the PVs, in 15% of the patients. PV diameter reduction was not related to changes in left atrial volume. Isolation of the pulmonary veins using a multielectrode ablation catheter and duty cycled phased radiofrequency energy delivery results in a consistent moderate reduction of the PV diameters predominantly at the ostium. Severe PVN in 15% of patients raises concerns about the risk for clinical PV stenosis.
    Circulation Arrhythmia and Electrophysiology 11/2011; 5(1):52-60. DOI:10.1161/CIRCEP.111.961888 · 5.42 Impact Factor
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    European journal of human genetics: EJHG 08/2010; 18(8):881. DOI:10.1038/ejhg.2010.37 · 4.23 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. DOI:10.1038/ejhg.2010.23 · 4.23 Impact Factor
  • Marc De Buyzere
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    ABSTRACT: An abstract is unavailable. This article is available as HTML full text and PDF.
    Journal of Hypertension 05/2009; 27(6):1327-1328. DOI:10.1097/HJH.0b013e32832bb86f · 4.22 Impact Factor

Publication Stats

69 Citations
51.82 Total Impact Points


  • 2009–2014
    • Ghent University
      • Department of Public Health
      Gand, Flemish, Belgium
  • 2010–2013
    • Universitair Ziekenhuis Ghent
      • Department of Cardiology
      Gand, Flanders, Belgium