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J H M Tulen

Publications and source records attributed to J H M Tulen.

8 recordsLinked to original sources
PubMed2005

Quantification of the dynamic behavior over time of narrow-band components present in heart rate variability by means of the instantaneous amplitude and frequency.

The statistical properties of the time- and frequency-domain characteristics of heart rate variability are known to vary over time. A method is presented to compute the time-varying spectral contents of the characteristic narrow-band frequency components of heart rate variability by means of the instantaneous amplitude and frequency at an optimal time resolution. The instantaneous frequency may show oscillatory, but also irregular periods in time. An index of the instantaneous bandwidth is computed to discriminate between oscillatory and irregular periods and to correct the instantaneous amplitude and frequency for irregular periods.

Algorithms↗
PubMed2004

Low body mass index is associated with an increased risk of neuropsychiatric adverse events and concentration impairment in women on mefloquine.

AIMS: We performed a prospective cohort study to gain more insight into risk factors for neuropsychiatric effects of mefloquine among tourists travelling to tropical areas. METHODS: We enrolled all patients who consulted the Travel Clinic of the Havenziekenhuis & Institute for Tropical Diseases Rotterdam for mefloquine prophylaxis during the period between 1 May 1999 and 7 March 2000. Each patient was followed from baseline (prior to starting mefloquine) up to 3 weeks after starting weekly intake of 250 mg mefloquine. We compared the intraindividual change in scores between baseline and follow-up visit on the Dutch shortened Profile of Mood States, and on the Continuous Performance Test (CPT) which measures sustained attention. RESULTS: The final cohort consisted of 151 subjects with a mean age of 38 years. In this population, a significant impairment of mood state was observed in those with a body mass index (BMI) < or = 20 kg m(-2). Stratification for gender showed that the total mood disturbance in females in the lowest BMI category significantly increased by 8.42 points [95% confidence interval (CI) 3.33, 13.50], whereas BMI did not affect the risk in males. Stratification for history of use of mefloquine showed that the risks were highest in first-time users. Analyses of the CPT showed that reaction time in women with a BMI < or = 20 kg m(-2) increased significantly by 22.5 ms (95% CI 7.80, 37.20), whereas reaction time in men showed a slight and nonsignificant decrease. CONCLUSION: Risk factors for mefloquine-associated neuropsychiatric adverse events and concentration impairment are female gender, low BMI, and first-time use. The frequency of neuropsychiatric effects is highest in women with a BMI < or = 20 kg m(-2).

Adolescent↗
PubMed2004

Cardiovascular risk factors in outpatients with bipolar disorder.

BACKGROUND: The mortality due to cardiovascular diseases in bipolar patients is much higher than in the general population. It is unclear whether lithium treatment contributes to this cardiovascular morbidity. METHODS: The cardiovascular risk factors in outpatients with bipolar disorder on monotherapy lithium were explored. Cardiac (family) history, important habits and recent stressful events were assessed. Quetelet Index (QI) was calculated and blood samples were taken. Blood pressure (BP) was measured in supine position and during orthostatic challenge. RESULTS: 40 out of 81 patients on monotherapy lithium were studied in detail. In this group, one patient was hypothyroid; six patients suffered from hypertension. QI was > 25 in 57.5% of the patients; mean cholesterol level was 5.7 mmol/L. Renal functioning, electrolytes and glucose concentrations were normal. There were no significant relationships between the duration of lithium treatment, the duration of bipolar disorder, recent stressful events and hypertension. Out of the group of 81 patients on lithium monotherapy, 13 patients in total used antihypertensive medication, indicating a high prevalence of hypertension in this group as compared to the general population. CONCLUSIONS: Cardiovascular risk factors, including hypertension, were increased in a large proportion of this population on monotherapy lithium. However, no significant relationships were observed between duration of lithium treatment or bipolar disorder and presence of hypertension.

Adult↗
PubMed2004

Interictal daily functioning in migraine.

Migraine induces disability and an impaired quality of life, even between attacks. As most studies are based on subjective reports only, this study was set up to objectively quantify the interictal daily activities and heart rate of migraine patients, in relation to their subjectively reported highest realizable level of activity and of symptoms of mood in their habitual environment. Measurements were obtained during a migraine-free 2-day period of 24 patients (age range: 21-57 years) and 24 controls (age range: 18-59 years). Accelerometry was used to quantify the time spent in different postures and movements. The subjective parameters were documented by daily log. Whereas heart rate was similar for patients and controls, migraineurs were found to be significantly less physically active than controls and reported a significantly lower realizable level of activity. In addition, when active, their body motility was less than that of controls. Migraine patients also showed a higher level of sleepiness and lower level of vigour. These interictal behavioural and subjective phenomena objectively illustrate the individual and societal burden of migraine and its chronic impact on both domains.

Activities of Daily Living↗
PubMed2003

The instantaneous frequency of cardiovascular time series: a comparison of methods.

The instantaneous frequency (IF) of cardiovascular time series is used to describe the time-varying spectral contents of the characteristic frequency bands that are of interest for psychophysiological and cardiovascular research. Four methods to compute IF of band-limited, monocomponent, and analytical cardiovascular time series were compared by means of simulated time series contaminated with additive noise. These four methods are: the method using the inverse Fourier transform of uncorrelated time-slices of the Wigner-Ville distribution, the discrete time-frequency transform, the circular mean direction of the time-slices of the Wigner-Ville distribution, and the central finite difference of the phase. The time resolution of the estimates is optimal and is inversely related to the bandwidth of the frequency components, as given by the uncertainty principle of Gabor. At periods in time where the signal fulfills the requirements of the model signal, the four estimates of IF are numerically equal; only the circular mean direction showed a slight deviation from the other estimates. Although the estimates of IF differ at sudden phase shifts at low amplitude, i.e. at points where the signal locally does not comply with the requirements of the model signal, overall the four methods produce comparable estimates of IF of a cardiovascular time series at an optimal time resolution.

Cardiovascular Physiological Phenomena↗
PubMed2002

Neuropsychiatric events during prophylactic use of mefloquine before travelling.

INTRODUCTION: It has been suggested that neuropsychiatric events during use of mefloquine are more common in females than in males and are partly explained by the psychological stress of travelling. Therefore, we investigated neuropsychiatric events in females and males on mefloquine in the 3-week prophylactic period that precedes travelling. Furthermore, we investigated whether first-time users had a higher risk of neuropsychiatric adverse events than subjects with a history of mefloquine use. METHODS: We enrolled all patients who visited a Travel Clinic for mefloquine prophylaxis during the period 1 May 1999 to 7 March 2000. Each patient was followed from baseline (prior to starting mefloquine) up to 3 weeks after the start of mefloquine but before travelling. We asked patients to register any adverse event in a diary and measured the intra-individual change in scores on the Dutch Shortened Profile Of Mood States (POMS) at baseline and at the end of follow-up. RESULTS: The final cohort consisted of 179 subjects with a mean age of 3 years. Females reported adverse events more frequently than males ( P=0.005). Overall, we observed a small but significant increase in the score on the domain fatigue [0.74 points, 95% confidence interval (CI) 0.18, 1.30]. The effect was exclusively present in females and not in males. First-time users of mefloquine increased 2.81 points (95% CI 0.70, 4.92) on the total score of the POMS, and among those, women showed the largest increase of 4.58 points (95% CI 0.74, 8.43). CONCLUSION: The use of mefloquine was associated with neuropsychiatric adverse effects. Females encountered neuropsychiatric effects more frequently than males, which could be confirmed by validated psychological tests. Neuropsychiatric effects were more common in first-time users than in individuals who had used mefloquine before.

Adolescent↗
PubMed2002

Spectral analysis of heart rate and blood pressure variability in primary Sjögren's syndrome.

BACKGROUND: Autonomic dysfunction has been described in primary Sjögren's syndrome (SS). OBJECTIVE: To investigate the circulatory autonomic regulation in patients with primary SS by power spectral analysis of heart rate and blood pressure variability. METHODS: Forty three (42 female) patients with primary SS, mean age 52 years (range 23-80), with a mean disease duration of eight years (range 1-30) and 30 (15 female) healthy controls, mean age 43 years (range 21-68) were studied. In each patient blood pressure, heart rate, and respiration were measured continuously during supine rest and orthostatic challenge (60 degrees head-up tilt). Power spectral analysis was performed to determine possible differences in short term sympathetic and parasympathetic autonomic regulation between patients and controls. Furthermore, spectral parameters were studied in relation to illness severity and disease duration of the patients with primary SS. RESULTS: After controlling for differences in age, heart rate variability of the mid-frequency band and the variation coefficient of systolic blood pressure were significantly lower in patients with primary SS than in controls during supine rest. During 60 degrees tilt patients with primary SS showed a significantly higher mean heart rate, mean systolic blood pressure, and variation coefficient of diastolic blood pressure, and a significantly lower baroreflex index than controls. After controlling for age, no differences were found either in heart rate variability, blood pressure results, and baroreflex sensitivity during supine rest and tilt between the subgroups divided according to disease duration, Schirmer test results, or between the subgroups with different fatigue scores. No differences were found in spectral data between the groups with and without positive antinuclear antibody serology. CONCLUSION: For the group no differences in sympathetic and parasympathetic cardiac control were seen between patients with primary SS and controls, as assessed by spectral techniques, although some cardiovascular differences were found, particularly during orthostatic challenge.

Adult↗