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J A Knottnerus

Publications and source records attributed to J A Knottnerus.

At least 19 recordsLinked to original sources
PubMed2006

Chronic fatigue syndrome-like caseness as a predictor of work status in fatigued employees on sick leave: four year follow up study.

OBJECTIVE: To assess whether CFS-like caseness (meeting the criteria for chronic fatigue syndrome (CFS)) predicts work status in the long term. METHODS: Prospective study in a sample of fatigued employees absent from work. Data were collected at baseline and four years later, and included CFS-like caseness and work status (inactive work status and full work incapacity). RESULTS: CFS-like cases at baseline were three times more likely to be unable to work at follow up than fatigued employees who did not meet CFS criteria at baseline (ORs 3-3.3). These associations grew even stronger when demographic and clinical confounders were controlled for (ORs 3.4-4.4). CONCLUSION: A CFS-like status (compared to non-CFS fatigue) proved to be a strong predictor of an inactive work status and full work incapacity in the long term. Since little is known about effective interventions that prevent absenteeism and work incapacity or facilitate return to work in subjects with chronic fatigue, there is a great need for powerful early interventions that restore or preserve the ability to work, especially for workers who meet criteria for CFS.

Absenteeism↗
PubMed2006

Lower prevalence of heart disease but higher mortality risk during follow-up was found among nonrespondents to a cohort study.

OBJECTIVE: The primary aim was to assess the association between response behavior and health status at baseline, and survival in a 5-year follow-up period. A secondary aim was to assess whether reasons for nonresponse were associated with health status at baseline. STUDY DESIGN AND SETTING: Data came from a prospective study cohort consisting of 31,349 men and women aged 45-70 years. Objective retrospective and prospective health information derived from general practitioner registries was available for both respondents and nonrespondents. RESULTS: Results show that among respondents coronary heart disease was more prevalent. Compared with respondents, noncontacts had a higher mortality risk during follow-up. Refusals had hypercholesterolemia more often than did noncontacts, and coronary heart disease or diabetes mellitus less often. CONCLUSION: The paradoxical results that respondents are less healthy at baseline but prospectively have a lower mortality risk may point to a selection effect indicating that the 'worried ill' are more inclined to participate. This effect could imply that observed relationships between risk factors or behaviors and outcomes in cohort studies may be attenuated.

Age Distribution↗
PubMed2006

Perceived quality of reproductive care for girls in a competitive voucher programme. A quasi-experimental intervention study, Managua, Nicaragua.

OBJECTIVE: To determine whether female adolescents from low-income areas in Managua were satisfied with the sexual and reproductive health (SRH) care provided through a competitive voucher programme and to analyse the determinants of their satisfaction. DESIGN: A community-based quasi-experimental intervention study from 2000 to 2002. SETTING: Low-income areas of Managua. INTERVENTION: Distribution of 28,711 vouchers giving adolescents free-access to SRH care in 19 clinics; training and support for health care providers. STUDY PARTICIPANTS: A random sample of 3009 girls from 12 to 20 years completed self-administered questionnaires: 700 respondents had used this care in the last 15 months, 221 with voucher (users-with-voucher) and 479 without voucher (users-without-voucher). MAIN OUTCOME MEASURES: User satisfaction; Satisfaction with clinic reception; Clarity of doctors' explanations. RESULTS: User satisfaction was significantly higher in users-with-voucher compared with users-without-voucher [Adjusted odds-ratio (AOR) = 2.2; 95% confidence interval (95% CI) = 1.2-4.0]. Voucher use was associated with more frequent satisfaction with clinic reception, especially among sexually active girls not yet pregnant or mother (AOR = 6.9; 95% CI = 1.5-31.8). The clarity of doctors' explanations was not perceived differently (AOR = 1.4; 95% CI = 0.9-2.2). User satisfaction was highly correlated to satisfaction with clinic reception and clarity of doctors' explanations (P < 0.001). Longer consultation times, shorter waiting times, older age, and having a female doctor positively influenced user satisfaction. CONCLUSION: Voucher use by teenage girls was associated with a better perceived SRH care. This is an important result, given the crucial role user satisfaction plays in adoption and continued use of health care and contraceptives. Though more research is needed, confidential and guaranteed access appear key factors to voucher success.

Adolescent↗
PubMed2006

Can a comprehensive voucher programme prompt changes in doctors' knowledge, attitudes and practices related to sexual and reproductive health care for adolescents? A case study from Latin America.

OBJECTIVES: To evaluate whether participation in a competitive voucher programme designed to improve access to and quality of sexual and reproductive health care (SRH-care), prompted changes in doctors' knowledge, attitudes and practices. METHODS: The voucher programme provided free access to SRH-care for adolescents. Doctors received training and guidelines on how to deal with adolescents, a treatment protocol, and financial incentives for each adolescent attended. To evaluate the impact of the intervention on doctors, nearly all participating doctors (n = 37) were interviewed before the intervention and 23 were interviewed after the intervention. Answers were grouped in subthemes and scores compared using nonparametric methods. RESULTS: The initial interviews disclosed deficiencies in doctors' knowledge, attitudes and practices relating to adolescent SRH-issues. Gender and age of the doctor were not associated with the initial scores. Comparing scores from before and after the intervention revealed significant increases in doctors' knowledge of contraceptives (P = 0.003) and sexually transmittable infections (P < 0.001); barriers to contraceptive use significantly diminished (P < 0.001 and P = 0.003); and some attitudinal changes were observed (0 = 0.046 and P = 0.11). Doctors became more aware of the need to improve their communication skills and were positive about the programme. CONCLUSIONS: This study confirmed provider related barriers that adolescents in Nicaragua may face and reinforces the importance of focusing on the quality of care and strengthening doctors' training. Participation in the voucher programme resulted in increased knowledge, improved practices and, to a lesser extent, in changed attitudes. A competitive voucher programme with technical support for the participating doctors can be a promising strategy to prompt change.

Adolescent↗
PubMed2006

Uncovering and responding to needs for sexual and reproductive health care among poor urban female adolescents in Nicaragua.

BACKGROUND: To meet the needs of female adolescents from low-income urban areas for sexual and reproductive health (SRH) care, vouchers providing free-of-charge access to SRH care at 19 primary care clinics were distributed in Managua, Nicaragua. These vouchers substantially increased the use of services, demonstrating that many adolescents are willing to use such services, if readily accessible. The voucher redemption made it possible to identify the nature of existing, but largely unmet, needs for SRH care. METHOD: The medical files from 3301 consultations with female adolescents were analysed using descriptive statistical methods and multiple logistic regression. RESULTS: Female adolescents presented SRH problems that merited medical attention. The mean number of problems presented was 1.5 per consultation: 34% of the vouchers were used for contraceptives, 31% for complaints related to sexually transmitted infection (STI) or reproductive tract infection (RTI), 28% for advice/counselling, 28% for antenatal check-up and 18% for pregnancy testing. A new category of health care users emerged: sexually active girls who were neither pregnant nor mothers and who sought contraceptives or STI/RTI treatment. Contraceptive use doubled among the sexually active non-pregnant voucher redeemers. Consultation with a female doctor younger than 36 years was associated with a higher chance of having contraceptives prescribed. CONCLUSION: Accessible and appropriate SRH care has the potential to make an important contribution to the increased contraceptive use, decreased risk of unwanted teenage pregnancies and decreased prevalence of STIs/RTIs among underserved adolescents. Once adolescents access the services, providers have a crucial role in ensuring current and continuing needs are met.

Adolescent↗
PubMed2006

The effects of 6 months of increased water intake on blood sodium, glomerular filtration rate, blood pressure, and quality of life in elderly (aged 55-75) men.

OBJECTIVES: To study whether there are any negative or positive effects of 6 months of increased fluid intake in reasonably healthy elderly men. DESIGN: Randomized trial. SETTING: Community-based. PARTICIPANTS: One hundred forty-one healthy participants aged 55 to 75. INTERVENTION: One group was given the advice to increase their daily fluid intake by 1.5 L of water; the other group was given placebo medication (8 mL inactive syrup per day). MEASUREMENTS: At 6 months blood sodium, glomerular filtration rate (GFR), blood pressure, and quality of life (QOL) were measured. The changes in water turnover were measured using deuterium. RESULTS: Most subjects did not manage to increase their fluid intake by 1.5 L. The average increase in the intervention group was approximately 1 L. Twenty-four-hour water turnover in the water group was 359 mL (95% confidence interval=171-548) higher than that of the control group at 6-month follow-up. Blood pressure, sodium level, GFR, and QOL did not change significantly in either group during the intervention period. In addition, the cases reporting a worsening on the effect measures were equally distributed over the two study groups. CONCLUSION: The advice to increase fluid intake by 1.5 L had no negative effects in reasonably healthy men aged 55 to 75.

Aged↗
PubMed2005

Clinical items not helpful in differentiating viral from bacterial lower respiratory tract infections in general practice.

OBJECTIVE: Incorrect and unnecessary antibiotic prescribing enhancing bacterial resistance rates might be reduced if viral and bacterial lower respiratory tract infections (LRTI) could be differentiated clinically. Whether this is possible is often doubted but has rarely been studied in general practice. STUDY DESIGN AND SETTING: This was an observational cohort study in 15 general practice surgeries in the Netherlands. RESULTS: Etiologic diagnoses were obtained in 112 of 234 patients with complete data (48%). Viral pathogens were found as often as bacterial pathogens. Haemophilus (para-) influenzae was most frequently found. None of the symptoms and signs correlated statistically significantly with viral or bacterial LRTI. Erythrocyte sedimentation rate >50 (odds ratio [OR] 2.3-3.3) and C-reactive protein (CRP) >20 (OR 2.1-4.6) were independent predictors for viral LRTI and bacterial LRTI when compared with microbiologically unexplained LRTI. CONCLUSION: Extensive history-taking and physical examination did not provide items that predict viral or bacterial LRTI in adult patients in daily general practice. We could not confirm CRP to differentiate between viral and bacterial LRTI.

Adult↗
PubMed2005

The validity and ethics of giving placebo in a randomized nonpharmacologic trial was evaluated.

OBJECTIVE: When studying the effects of a non-pharmacologic intervention, the choice of a control group is often difficult. In a study on the effectiveness of increased water intake on voiding dysfunction in elderly men we used an unusual design. This article addresses the internal validty and ethics of this design. STUDY DESIGN AND SETTING: The randomized trial we evaluated had a 6-month follow-up period and was carried out among 141 elderly men with moderate lower urinary tract symptoms. The experimental group was given the instruction to drink more water, the control group received placebo medication. The participants were not informed that there was a 50% chance of receiving placebo. We measured whether the prior expectations and preferences were comparable for the two study groups, whether blinding was preserved throughout the study period, and whether the participants considered this design ethical. RESULTS: Prior to randomization, patients had higher expectations for the experimental intervention, but there was not statistically significant difference in their preference. During the study period, two out of 71 patients in the control group unmasked the placebo. In general, both groups fully agreed with the informed consent procedure. CONCLUSION: This design can be considered when the effects of a non-pharmacologic interventions are studied.

Aged↗
PubMed2005

Prenatal exposure to mite and pet allergens and total serum IgE at birth in high-risk children.

To examine the relationship between prenatal exposure to mite, cat and dog allergens and total serum IgE at birth in newborns at high risk of asthma. In the homes of 221 newborns with at least one first-degree relative with asthma, concentrations (ng/g dust) of allergens of house dust mite (mite), cat and dog were measured at the fourth to sixth month of pregnancy in dust samples from the maternal mattress and living room. At day 3-5 after birth, total IgE was measured in capillary heel blood. A total number of 174 blood samples were available (11 mothers refused newborn's blood sampling, and in 36 cases the blood sample was too small for analysis). In 24% of the newborns, total IgE was elevated (cut-off value 0.5 IU/ml). A significant dose response relationship was found between increasing mite allergen levels [divided in quartiles ng/g dust (qrt)] and the percentage of elevated IgE: first qrt (0-85 ng/g) 13%; second qrt (86-381) 19%; third qrt (382-2371) 26%; fourth qrt (> or =2372) 42%, respectively, p=0.01. This relationship remained significant after adjusting for passive smoking, maternal and paternal mite allergy, socio-demographic factors, birth characteristics and (breast) feeding practice in the first week of life. In high-risk newborns, prenatal exposure to mite allergens, but not to cat and dog allergens from dust of the living room and of the maternal mattress was associated with total serum IgE at birth.

Allergens↗
PubMed2005

Increasing the daily water intake for the prophylactic treatment of headache: a pilot trial.

Dehydration is commonly believed to result in headache, but the effectiveness of increasing the water intake in patients who frequently suffer from headaches has not been studied thus far. In a pilot study, we examined the possible effects and feasibility of increased water intake in headache patients. Eighteen headache patients (all had migraine, two also had tension-type headache) were randomly allocated to placebo medication, or the advice to additionally drink 1.5 l of water per day, for a period of 12 weeks. Effect measurements consisted of a 2 weeks headache diary and the Migraine Specific Quality of Life (MSQOL) questionnaire. The advice to increase the daily fluid intake by 1.5 l increased the fluid intake in the intervention group by approximately 1 l. This reduced the total hours of headache in 2 weeks by 21 h (95% CI: -48 to 5). Mean headache intensity decreased by 13 mm (95% CI: -32 to 5) on a visual analogue scale (VAS). The effects on MSQOL, number of headache episodes, and medication seemed to be small. The data of the present study suggest a reduction in the total number of hours and intensity of headache episodes after increased water intake. Our results seem to justify larger scaled research on the effectiveness of increased water intake in headache patients.

Confidence Intervals↗
PubMed2005

The PREVASC study: the clinical effect of a multifaceted educational intervention to prevent childhood asthma.

As asthma is the most common chronic disease in childhood, much attention is directed towards primary prevention. Here, the clinical effectiveness of a multifaceted educational prevention was studied. A total of 476 high-risk children were recruited during the prenatal period by general practitioners and randomised to either: 1) a control group, receiving usual care; or 2) an intervention group in which families received instruction from nurses on how to reduce exposure of newborns to mite, pet and food allergens, and passive smoking. A total of 443 infants were followed-up for 2 yrs. At 2 yrs of age, the intervention group (n = 222) had less asthma-like symptoms, including wheezing, shortness of breath and night-time cough, than the control group (n = 221). No significant differences in total and specific immunoglobulin E were found between the groups. During the first 2 yrs of life, the incidence of asthma-like symptoms was similar in both groups; however, subanalysis revealed a significant reduction in the female, but not in the male, intervention group. In conclusion, the intervention used in this study was not effective in reducing asthma-like symptoms in high-risk children during the first 2 yrs of life, although it was modestly effective at 2 yrs. Follow-up is necessary to confirm whether the intervention can actually prevent the development of asthma.

Adult↗
PubMed2004

Measurement of lifetime alcohol intake: utility of a self-administered questionnaire.

Prior epidemiologic research revealing cardioprotective effects of alcohol intake has systematically neglected lifetime exposure to alcohol, which may cause serious bias in conclusions regarding drinking and heart disease risk. Departing from use of an earlier interview schedule, the authors of the present 1996-2001 cohort study developed a self-administered Lifetime Drinking History questionnaire (LDH-q). A total of 16,211 Dutch men and women older than age 45 years participated by completing the baseline questionnaire. A random sample of 3,255 men and women was used to determine the reliability and validity of the LDH-q. Test-retest reliability was assessed by means of the intraclass correlation coefficient and kappa scores. Correlations between lifetime and current intake scores were used to assess discriminant and convergent validity. Both reliability and validity appeared to be reasonably high compared with results obtained by using interview formats to measure lifetime alcohol intake. Reliability of the LDH-q was higher for men than for women, probably because of the more frequent and regular drinking of men. Indices of validity were similar for men (0.75) and women (0.70). Results show that the LDH-q can be a useful instrument in large-scale cohort studies.

Adult↗
PubMed2004

Systematic review: the role of different types of fibre in the treatment of irritable bowel syndrome.

BACKGROUND: Both high-fibre dietary advice and the prescription of fibre as a bulking agent are very common in primary and secondary care management of irritable bowel syndrome. Irritable bowel syndrome patients with constipation may have delayed intestinal transit. Therefore, fibres that accelerate intestinal transit may be beneficial in these patients. The uncertain benefits reported in several clinical studies, however, have led us to reappraise the value of fibre in irritable bowel syndrome management. AIM: To quantify the effect of different types of fibre on global and symptom relief from irritable bowel syndrome. METHODS: Using a structured literature search in MEDLINE (1966-2002), we selected randomized controlled trials involving irritable bowel syndrome patients treated with fibre. Analyses were performed for the total group and for trials using soluble and insoluble fibre separately. RESULTS: Seventeen studies were included in the analysis. None investigated primary care irritable bowel syndrome patients. Fibre, in general, was effective in the relief of global irritable bowel syndrome symptoms [relative risk, 1.33; 95% confidence interval (CI), 1.19-1.50]. Irritable bowel syndrome patients with constipation may receive benefit from fibre treatment (relative risk, 1.56; 95% CI, 1.21-2.02), but there was no evidence that fibre was effective in the relief of abdominal pain in irritable bowel syndrome. Soluble and insoluble fibre, separately, had different effects on global irritable bowel syndrome symptoms. Soluble fibre (psyllium, ispaghula, calcium polycarbophil) showed significant improvement (relative risk, 1.55; 95% CI, 1.35-1.78), whereas insoluble fibre (corn, wheat bran), in some cases, worsened the clinical outcome, but there was no significant difference compared with placebo (relative risk, 0.89; 95% CI, 0.72-1.11). CONCLUSIONS: The benefits of fibre in the treatment of irritable bowel syndrome are marginal for global irritable bowel syndrome symptom improvement and irritable bowel syndrome-related constipation. Soluble and insoluble fibres have different effects on global irritable bowel syndrome symptoms. Indeed, in some cases, insoluble fibres may worsen the clinical outcome. Future clinical studies evaluating the effect and tolerability of fibre therapy are needed in primary care.

Colonic Diseases, Functional↗
PubMed2004

Asymptomatic peripheral arterial occlusive disease predicted cardiovascular morbidity and mortality in a 7-year follow-up study.

OBJECTIVE: Asymptomatic peripheral arterial occlusive disease (PAOD) is a common atherosclerotic disorder among the elderly population. Scarce data are available on the risk of nonfatal and fatal cardiovascular diseases in these subjects. We investigated cardiovascular morbidity and mortality of asymptomatic PAOD subjects. STUDY DESIGN AND SETTING: A sample of 3649 subjects (40-78 years of age) was selected in collaboration with 18 general practice centers and followed up after the initial screening (mean follow-up time 7.2 years). Asymptomatic PAOD was determined by means of the ankle-brachial pressure index (ABPI). Main outcome measures were nonfatal cardiovascular events and mortality. RESULTS: Cox proportional hazard models showed that asymptomatic PAOD was significantly associated with cardiovascular morbidity (hazard ratio [HR] 1.6, 95% confidence interval [CI] 1.3-2.1), total mortality (HR 1.4, 95% CI 1.1-1.8), and cardiovascular mortality (HR 1.5, 95% CI 1.1-2.1). CONCLUSION: Asymptomatic PAOD is a significant predictor of cardiovascular morbidity and mortality. In high-risk subjects, measurement of the ABPI provides valuable information on future cardiovascular events.

Adult↗
PubMed2004

Pathophysiological aspects of bladder dysfunction: a new hypothesis for the prevention of 'prostatic' symptoms.

This article reviews the literature on the pathophysiology of male lower urinary tract symptoms (LUTS) with the intention of developing a new preventive intervention for this bothersome disease. Traditionally, male voiding dysfunction has been thought to arise from bladder outlet obstruction (BOO) caused by prostatic enlargement. Many years of research, however, have shown that a clear relationship between the size of the prostate and the occurrence or severity of symptoms is doubtful. Because of its crucial role in urination, it is increasingly being accepted that the clinical manifestation of voiding dysfunction relies on the functional behaviour of the bladder. Several animal studies have shown that bladder performance can be improved by increasing urine output. Contrary to alterations observed in pathologic situations, an increased urine output provides a physiologic stimulus for animal bladder function improvement. We hypothesise that a trained bladder should be less susceptible to the harmful effects of ageing and obstruction. Future symptoms may thus be prevented. In humans an increased urine output can be achieved by drinking additional water, which could be an adequate preventive intervention.

Aging↗
PubMed2004

No clinical evidence base to support the hygiene hypothesis.

The hygiene hypothesis is a popular explanation for recent increases in allergy in the western world. This hypothesis suggests that development of allergy (or asthma) could be prevented by exposure to immune stimulants such as viruses, bacteria and endotoxins, in particular in the prenatal period or early childhood. How evidence-based are the observations which support the hygiene hypothesis? All clinical epidemiological indications in favour of the hypothesis are based on observational (cross-sectional and cohort) studies and not on observations in randomised controlled intervention studies. In cross-sectional studies no causal relationships can be assessed with sufficient validity. Also in cohort studies there are validity problems, as the exposure is not determined by chance (by means of randomisation) and could be influenced by behaviour. And behaviour might well be a confounder, since it can be associated with both exposure and outcome. A problem is that, without being appropriately tested in well designed prospective research, the hygiene hypothesis has currently already become so popular in the news media that an increased occurrence of asthma might even be induced as a result of an increased exposure. Although the currently available evidence to support the hygiene hypothesis is poor, it appears that the hypothesis has to some become a matter of faith or ideology. Scientists should take care that messages imparted to the general public do not go beyond or conflict with existing evidence.

Comment↗