Boer, A. de

Electrocardiographic characteristics of patients with chronic obstructive pulmonary disease (Article)

2013-02-01T00:00:00Z

Patients with chronic obstructive pulmonary disease (COPD) are at increased risk of cardiovascular disease. Electrocardiography (ECG) carries information about cardiac disease and prognosis, but studies comparing ECG characteristics between patients with and without COPD are lacking. We related ECG characteristics of patients with COPD, to ECG characteristics of patients without COPD, and determined whether ECG abnormalities are related to COPD severity. A cross-sectional study was conducted within a cohort of 243 COPD patients, aged 65 years or older. All patients underwent extensive examinations, including resting 12-lead ECG and pulmonary function tests. The reference group (n = 293) was a sample from the general population, also aged 65 or older, without COPD. Abnormal ECGs were more prevalent in COPD patients (50%) than in patients without COPD (36%, p = 0.054). Conduction abnormalities were the most common ECG abnormality in COPD patients (28%) being significantly more prevalent than in patients without COPD (11%, p < 0.001). The mean heart rate was higher in COPD patients (72 bpm (SD 14)) compared to controls (65 bpm (SD 13), p < 0.001), and QTc prolongation was less frequent in COPD patients (9% versus 14%, p = 0.01). The prevalence of ECG abnormalities increased with severity of pulmonary obstruction. ECG abnormalities, especially conduction abnormalities are common in COPD patients, and the prevalence of ECG abnormalities increases with severity of COPD. This underlines the importance of an integrated-care approach for COPD patients, paying attention to early detection of unrecognized coexisting cardiac disorders.

The effect of omeprazole and esomeprazole on the maintenance dose of phenprocoumon (Letter To Editor)

2012-12-01T00:00:00Z

The response to vitamin K antagonists (VKAs) is determined by many different factors like age, weight, height, vitamin K intake and genetic polymorphisms [1]. The proton pump inhibitors (PPIs) omeprazole and esomeprazole may enhance the effect of VKAs by inhibition of the hepatic metabolism of coumarins [2]. Some isolated cases have been reported of clinically significant elevated INRs in patients concomitantly using omeprazole and phenprocoumon, a VKA frequently used in Europe [3].Practical experience suggests an interaction between omeprazole or esomeprazole and phenprocoumon, but scientific evidence is still lacking.

Cost-effectiveness of pharmacogenetics in anticoagulation: International differences in healthcare systems and costs (Article)

2012-09-01T00:00:00Z

Genotyping patients for CYP2C9 and VKORC1 polymorphisms can improve the accuracy of dosing during the initiation of anticoagulation with vitamin K antagonists (coumarin derivatives). The anticipated degree of improvement in the safety of anticoagulation with coumarins through genotyping may vary depending on the quality of patient care, which varies both with and among countries. The management and the cost of anticoagulant care can therefore influence the cost-effectiveness of genotyping within any given country. In this article, we provide an overview of the cost-effectiveness of pharmacogenetics-guided dosing of coumarin derivatives. We describe the organization of anticoagulant care in the UK, Sweden, The Netherlands, Greece, Germany and Austria, where a genotype-guided dosing algorithm is currently being investigated as part of the EU-PACT trial. We also explore the costs of anticoagulant care for the treatment of atrial fibrillation in these countries.

Long-term anticoagulant effects of the CYP2C9 and VKORC1 genotypes in acenocoumarol users (Article)

2012-04-01T00:00:00Z

Background: The required acenocoumarol dose and the risk of underanticoagulation and overanticoagulation are associated with the CYP2C9 and VKORC1 genotypes. However, the duration of the effects of these genes on anticoagulation is not yet known. Objectives: In the present study, the effects of these polymorphisms on the risk of underanticoagulation and overanticoagulation over time after the start of acenocoumarol were investigated. Patients/methods: In three cohorts, we analyzed the relationship between the CYP2C9 and VKORC1 genotypes and the incidence of subtherapeutic or supratherapeutic International Normalized Ratio (INR) values (<2 and >3.5) or severe overanticoagulation (INR>6) for different time periods after treatment initiation. Results: Patients with polymorphisms in CYP2C9 and VKORC1 had a higher risk of overanticoagulation (up to 74%) and a lower risk of underanticoagulation (down to 45%) in the first month of treatment with acenocoumarol, but this effect diminished after 1-6months. Conclusions: Knowledge of the patient's genotype therefore might assist physicians to adjust doses in the first month(s) of therapy.

Future of Pharmacogenetics in Cardiovascular Diseases (In Book)

2012-01-01T00:00:00Z

Introduction: Pharmacogenetics is the study of variations in DNA sequence as related to drug response (European Medicines Agency [EMA], 2007). Several gene-drug interactions have been discovered in the field of cardiovascular diseases (CVDs). These gene-drug interactions can help to identify nonresponse to drugs, estimate dose requirements or identify an increased risk of developing adverse drug reactions. An individualized approach based on pharmacogenetic testing will provide physicians and pharmacists with tools for decision making about pharmacotherapy. While pharmacogenetic testing is already part of everyday practice in oncology, it is not widely implemented in the field of CVDs. However, in the near future, pharmacogenetics will probably also play a valuable role in this field as well.

Pharmacogenetic interactions between ABCB1 and SLCO1B1 tagging SNPs and the effectiveness of statins in the prevention of myocardial infarction (Article)

2010-08-01T00:00:00Z

Aims: Genetic variability within the SLCO1B1 and ABCB1 transporter genes has been associated with modification of statin effectiveness in cholesterol management. Materials & methods: We conducted a case-control study using a population-based registry of pharmacy records linked to the hospital discharge records. Within a hypercholesterolemic cohort, we included 668 myocardial infarction cases and 1217 controls. Results: We tested 24 tagging SNPs and found two SNPs within ABCB1 (rs3789244, p = 0.01; rs1922242, p = 0.01) to interact with statin treatment. In addition, we found a nonsignificant haplotype-treatment interaction (p = 0.054). The odds ratio for subjects homozygous for SLCO1B1*1A was 0.49 (95% CI: 0.34-0.71) compared with 0.31 (95% CI: 0.24-0.41) for heterozygous or noncarriers of the *1A allele. Conclusion: This is the first study to demonstrate that common genetic variability within the SLCO1B1 and ABCB1 genes is associated with the modification of the effectiveness of statins in the prevention of the clinical outcome, myocardial infarction.

Clinical and economic consequences of pharmacogenetic-guided dosing of warfarin (Article)

2010-08-01T00:00:00Z

Patients using warfarin for oral anticoagulant therapy need to be frequently monitored because of warfarins narrow therapeutic range and the large variation in dose requirements among patients. Patients receiving the wrong dose have an increased risk of bleeding or thromboembolic events. The required dose is influenced by environmental factors, such as gender, age, diet and concomitant medication, as well as genetic factors. Pharmacogenetic testing prior to warfarin initiation might improve dosing accuracy and, therefore, safety and efficacy of warfarin treatment. Meckley et al. studied the clinical consequences and costs of genotyping before warfarin treatment. The results of their study suggest that pharmacogenetic-guided dosing of patients initiating warfarin could improve health (quality-adjusted life-years) but at a high cost per quality-adjusted life-year gained. Owing to the inevitable assumptions that have to be made in all cost-effectiveness models, great uncertainty remains regarding the cost-effectiveness of pharmacogenetic-guided warfarin dosing.

A systematic review of cost-effectiveness analyses of pharmacogenetic- guided dosing in treatment with coumarin derivatives (Article)

2010-07-01T00:00:00Z

Anticoagulant therapy with coumarin derivatives is often sub-or supra-therapeutic, resulting in an increased risk of thromboembolic events or hemorrhage, respectively. Pharmacogenetic-guided dosing has been proposed as an effective way of reducing bleeding rates. Clinical trials to confirm the safety, efficacy and effectiveness of this strategy are ongoing, but in addition, it is also necessary to consider the cost-effectiveness of this strategy. This article describes the findings of a systematic review of published cost-effectiveness analyses of pharmacogenetic-guided dosing of coumarin derivatives. Similarities and differences in the approaches used were examined and the quality of the analyses was assessed. The results of the analyses are not sufficient to determine whether or not pharmacogenetic-guided dosing of coumarins is cost effective. More reliable cost-effectiveness estimates need to become available before it is possible to recommend whether or not this strategy should be applied in clinical practice.

Use of proton pump inhibitors and risk of hip/femur fracture: a population-based case-control study (Article)

2010-01-01T00:00:00Z

Summary: Previous studies evaluated the association between proton pump inhibitor (PPI) use and subsequent fracture risk, but they showed ambiguous results. Therefore, the objective was to evaluate this association in a different study population. Our findings show that there is probably no causal relationship between PPI use and hip fracture risk. Introduction: Previous studies evaluated the association between PPI use and subsequent fracture risk, but they showed ambiguous results. To further test these conflicting results, the objective of this study was to evaluate the association between the use of PPIs and the risk of hip/femur fracture in a different study population. Methods: A case-control study was conducted using data from the Dutch PHARMO record linkage system. The study population included 6,763 cases aged 18 years and older with a first hip/femur fracture during enrolment and 26,341 age-, gender- and region-matched controls. Results: Current users of PPIs had an increased risk of hip/femur fracture yielding an adjusted odds ratio (AOR) of 1.20 (95% CI 1.04-1.40). Fracture risk attenuated with increasing durations of use, resulting in AORs of 1.26 (95% CI 0.94-1.68) in the first 3 months, 1.31 (95% CI 0.97-1.75) between 3 and 12 months, 1.18 (95% CI 0.92-1.52) between 13 and 36 months and 1.09 (95% CI 0.81-1.47) for use longer than 36 months. Conclusion: Our findings show that there is probably no causal relationship between PPI use and hip fracture risk. The observed association may be the result of unmeasured distortions: although current use of PPIs was associated with a 1.2-fold increased risk of hip/femur fracture, the positive association was attenuated with longer durations of continuous use. Our findings do not support that discontinuation of PPIs decreases risk of hip fracture in elderly patients.

Reasons for non-response in observational pharmacogenetic research (Article)

2009-11-27T00:00:00Z

Purpose: In epidemiological studies, non-response may introduce bias and limit generalizability. In genetic pharmacoepidemiological research, collection of DNA might be a major reason for non-response.We determined reasons for non-response and compared characteristics of non-responders and responders in a pharmacogenetic case-control study. Methods: Myocardial infarction (MI) cases and controls, who were antihypertensive drug users, were recruited through community pharmacies that participate in the Pharmaco-Morbidity-Record-Linkage- System (PHARMO). The PHARMO database comprises drug dispensing histories of about 2 000 000 subjects from a representative sample of Dutch community pharmacies linked to the national registry of hospital discharges. Independent samples t-test and ANOVA-statistics were used to analyse the differences in continuous variables between responders and non-responders. χ2 statistics and logistic regression were used to compare categorical variables. Results: We approached 1871 cases and 14 102 controls of whom 794 MI cases (42.4%) and 4997 controls (35.4%) responded. We could not approach 2194 patients of whom 63.1% had died and 31.2% moved to another pharmacy. Main reasons for non-response were health problems or hospital stays (16.2%, OR 1.47; 95%CI: 1.00-2.16). Other reasons were old age or dementia (16.9%, OR 1.82; 95%CI: 1.24-2.65). Only a small percentage (1.1%, OR 1.43; 95%CI: 0.41-5.03) mentioned DNA sampling as a reason. About 30% of the non-responders did not give a reason. Women were statistically significantly (p<0.0005) less willing to participate than men (38.8% versus 31.3%). An association with age was also found (mean age 64.6 versus 66.5 yrs) ( p<0.0005). Conclusion: In a pharmacogenetic case-control study fear for genetic screening was not a major reported reason for non-response. Females were less willing to participate than males.

Determinants of DNA yield and purity collected with buccal cell samples (Article)

2009-11-01T00:00:00Z

Buccal cells are an important source of DNA in epidemiological studies, but little is known about factors that influence amount and purity of DNA. We assessed these factors in a self-administered buccal cell collection procedure, obtained with three cotton swabs. In 2,451 patients DNA yield and in 1,033 patients DNA purity was assessed. Total DNA yield ranged from 0.08 to 1078.0 μg (median 54.3 μg; mean 82.2 μg ± SD 92.6). The median UV 260:280 ratio, was 1.95. Samples from men yielded significantly more DNA (median 58.7 μg) than those from women (median 44.2 μg). Diuretic drug users had significantly lower purity (median 1.92) compared to other antihypertensive drug users (1.95). One technician obtained significantly lower DNA yields. Older age was associated with lower DNA purity. In conclusion, DNA yield from buccal swabs was higher in men and DNA purity was associated with age and the use of diuretics.

Genotype-guided dosing of coumarin derivatives: the European pharmacogenetics of anticoagulant therapy (EU-PACT) trial design (Article)

2009-10-01T00:00:00Z

The narrow therapeutic range and wide interpatient variability in dose requirement make anticoagulation response to coumarin derivatives unpredictable. As a result, patients require frequent monitoring to avert adverse effects and maintain therapeutic efficacy. Polymorphisms in VKORC1 and CYP2C9 jointly account for about 40% of the interindividual variability in dose requirements. To date, several pharmacogenetic-guided dosing algorithms for coumarin derivatives, predominately for warfarin, have been developed. However, the potential benefit of these dosing algorithms in terms of their safety and clinical utility has not been adequately investigated in randomized settings. The European Pharmacogenetics of Anticoagulant Therapy (EU-PACT) trial will assess, in a single-blinded and randomized controlled trial with a follow-up period of 3 months, the safety and clinical utility of genotype-guided dosing in daily practice for the three main coumarin derivatives used in Europe. The primary outcome measure is the percentage time in the therapeutic range for international normalized ratio. This report describes the design and protocol for the trial.

Estimated age- and sex-specific incidence and prevalence of dopamine agonist-treated hyperprolactinemia (Article)

2009-08-01T00:00:00Z

Context: Few data exist on sex- and age-specific incidence and prevalence of idiopathic hyperprolactinemia and prolactinomas. Objectives: Our objective was to assess incidence and prevalence of dopamine agonist-treated hyperprolactinemia by age and sex. Design: From the PHARMO network, we identified an open cohort of patients who were ever dispensed dopamine agonists for hyperprolactinemia. The network includes complete medication histories for more than 2 million community-dwelling residents. Prolonged use of low-dose dopamine agonist is a reliable marker for hyperprolactinemia, provided that use for Parkinson's disease and lactation withdrawal is excluded. Diagnoses were verified by prolactin values in a random subsample using the same network. Results: We identified 11,314 subjects with at least one dispensing of dopamine agonist in the period 1996-2006, of whom 1607 subjects were considered to have dopamine agonist-treated hyperprolactinemia based on the prescribing pattern. The majority of patients were women (n = 1342, 84%). The diagnosis proved to be incorrect in only 1.5% of a random subsample. The estimated incidence rate of dopamine agonist-treated hyperprolactinemia for women was 8.7/100,000 person-years and for men 1.4/100,000 person-years. The highest incidence rate was found in women 25-34 yr of age: 23.9/100,000 person-years. The mean prevalence of ever treated female patients was almost five times higher (93.9/100,000) compared with male patients (19.6/100,000). Conclusion: The incidence rates and the prevalence of dopamine agonist-treated hyperprolactinemia showed an overall preponderance in women, with a strong peak for women aged 25-34 yr. In men, no peak was found. Copyright

Reply (Article)

2009-06-01T00:00:00Z

Recruitment of participants through community pharmacies for a pharmacogenetic study of antihypertensive drug treatment (Article)

2009-04-01T00:00:00Z

Objective To describe the design, recruitment and baseline characteristics of participants in a community pharmacy based pharmacogenetic study of antihypertensive drug treatment. Setting: Participants enrolled from the population-based Pharmaco-Morbidity Record Linkage System. Method We designed a nested case-control study in which we will assess whether specific genetic polymorphisms modify the effect of antihypertensive drugs on the risk of myocardial infarction. In this study, cases (myocardial infarction) and controls were recruited through community pharmacies that participate in PHARMO. The PHARMO database comprises drug dispensing histories of about 2,000,000 subjects from a representative sample of Dutch community pharmacies linked to the national registrations of hospital discharges. Results In total we selected 31010 patients (2777 cases and 28233 controls) from the PHARMO database, of whom 15973 (1871 cases, 14102 controls) were approached through their community pharmacy. Overall response rate was 36.3% (n = 5791, 794 cases, 4997 controls), whereas 32.1% (n = 5126, 701 cases, 4425 controls) gave informed consent to genotype their DNA. As expected, several cardiovascular risk factors such as smoking, body mass index, hypercholesterolemia, and diabetes mellitus were more common in cases than in controls. Conclusion Furthermore, cases more often used beta-blockers and calcium-antagonists, whereas controls more often used thiazide diuretics, ACE-inhibitors, and angiotensin-II receptor blockers. We have demonstrated that it is feasible to select patients from a coded database for a pharmacogenetic study and to approach them through community pharmacies, achieving reasonable response rates and without violating privacy rules.

Pharmacogenetics of cardiovascular drug therapy (Article)

2009-01-01T00:00:00Z

In developed countries cardiovascular disease is one of the leading causes of death. Cardiovascular drugs such as platelet aggregation inhibitors, oral anticoagulants, antihypertensives and cholesterol lowering drugs are abundantly prescribed to reduce risk of cardiovascular disease. Notable interindividual variation exists in the response to these pharmacotherapeutic interventions, which can be partially explained by factors such as gender, age, diet, concomitant drug use and environmental factors. Notwithstanding, a great part of this variability remains unknown. To a smaller or larger extent, genetic variability may contribute to the variability in response to these cardiovascular drugs. This review gives an overview of pharmacogenetic studies of genes that were reported to be associated with four commonly prescribed drugs/drug classes (platelet aggregation inhibitors, coumarins, antihypertensives and statins) and were studied at least 2 times with a similar outcome measure. In the field of cardiovascular drug therapy, polymorphisms in candidate genes such as the cycloxygenase-1, vitamin K reductase complex subunit 1, CYP2C9, alpha adducin and 3-hydroxy-3-methylglutaryl-CoA reductase have received a great amount of interest in the pharmacogenetics of aspirin, coumarins, antihypertensives and statins respectively. However, only variations in VKORC1 and CYP2C9 have consistently been associated with drug response (coumarins) and have clinical implications. Clinical trials should provide evidence for the effectiveness of genotyping before this procedure will be a part of every day anticoagulant therapy. In spite of the tremendous amount of publications in this field, there is no reason to advocate for genetic testing for any other drugs cardiovascular drug therapy yet. Current approaches in pharmacogenetic research do not seem to lead to results that meet our expectations of individualized medicine. Therefore, new approaches are needed addressing issues and challenges such as the number of SNPs studied, study power, study design and application of new statistical methods in (pharmaco-)genetic analysis.

Interaction between the Gly460Trp α-adducin gene variant and diuretics on the risk of myocardial infarction (Article)

2009-01-01T00:00:00Z

Introduction: The Gly460Trp variant of the α-adducin gene has been associated with the salt-sensitive and diuretic responsive form of hypertension. Objective: The aim of the study was to determine whether the α-adducin 460Trp variant allele modifies the risk-lowering effect of diuretics on myocardial infarction (MI). Design, Setting and Participants: In a population-based registry of pharmacy records linked to hospital discharge records (PHARMO), we used a nested case-control design. We selected patients hospitalized for MI as cases if they had at least one prescription for antihypertensive drugs in the 3 months prior to their first MI and were registered in PHARMO for at least 1 year. Controls that were matched on age, sex, region and calendar date, met the same eligibility criteria as the patients, but were not hospitalized for MI. Only current users of antihypertensive drugs in whom the Gly460Trp polymorphism was genotyped were included for this study. Logistic regression analysis was used to calculate odds ratio (OR), synergy indices, 95% confidence intervals (CIs) and to adjust for the potential confounding factors high cholesterol, smoking, BMI, diabetes, physical activity, alcohol use, use of loop diuretics, coumarins, antiplatelet drugs, ischemic heart disease and number of antihypertensive drugs. Results: The study included 613 patients and 3627 controls. Compared with users of other antihypertensives, the risk of MI was significantly lower among users of thiazide diuretics (OR 0.71, 95% CI 0.55-0.92). Among patients with the adducin variant the risk of MI was similar among thiazide users as compared with users of other antihypertensives (OR 0.88, 95% CI 0.58-1.33), whereas among wild-type carriers this risk was significantly lower (OR 0.62, 95% CI 0.44-0.87). The interaction between current use of diuretics and the α-adducin polymorphism was not statistically significantly increased on the multiplicative scale (synergy index 1.41, 95% CI 0.91-2.17). In sensitivity analyses, we found a nonsignificant trend towards a difference between patients who used potassium-sparing diuretics (synergy index 0.98, 95% CI 0.45-2.12) and patients who did not use potassium-sparing diuretics (synergy index 1.60, 95% CI 0.98-2.60) and a statistically significant difference between patients on monotherapy (synergy index 0.69, 95% CI 0.30-1.59) and those on combination therapy (synergy index 1.90, 95% CI 1.04-3.47). Conclusion: This study suggests that the α-adducin gene does not play an important role in modifying the risk of nonfatal MI associated with the use of thiazide diuretics.

Effectiveness of statins in the reduction of the risk of myocardial infarction is modified by the GNB3 C825T variant (Article)

2008-07-01T00:00:00Z

INTRODUCTION: The GNB3 C825T polymorphism has been shown to affect lipid parameters, atherosclerosis progression, and incidence of myocardial infarction (MI). Therefore, we assessed whether the effectiveness of statins in reducing the risk of MI was modified by the GNB3 C825T polymorphism. METHODS: In a population-based registry of pharmacy records linked to hospital discharge records (PHARMO), we used a nested case-control design. We selected patients hospitalized for MI as cases if they used antihypertensive drugs and had a diagnosis of hypercholesterolemia before their first MI. Controls met the same eligibility criteria, but were not hospitalized for MI. Logistic regression analysis was used to calculate odds ratios (OR) and synergy index with corresponding 95% confidence intervals (CI), and to adjust for potential confounding factors. RESULTS: We included 459 cases and 1805 controls. The risk of MI was significantly lower among participants exposed to statins compared with participants not exposed to statins (adjusted OR: 0.37, 95% CI: 0.29-0.47). The GNB3T allele was associated with a reduced risk of MI (adjusted OR: 0.74, 95% CI: 0.60-0.92). Among homozygous wild-type (CC) individuals (n=1119), exposure to statins was associated with a lower risk of MI (OR: 0.48, 95% CI: 0.34-0.67). However, T allele carriers (CT and TT) who used statins had an even stronger reduced risk of MI (OR: 0.27, 95% CI: 0.19-0.39). Overall, the interaction between exposure to statins and the GNB3 C825T polymorphism was significantly increased on the multiplicative scale (synergy index: 1.67, 95% CI: 1.06-2.65). CONCLUSION: Our findings show that T allele carriers of the GNB3 C825T polymorphism have less risk of MI and are more likely to benefit from statin therapy in a hypercholesterolemic population of antihypertensive drug users.

Comparison of different pain scoring systems in critically ill patients in a general ICU (Article)

2008-02-16T00:00:00Z

Background: Pain in critically ill patients in the intensive care unit (ICU) is common. However, pain assessment in critically ill patients often is complicated because these patients are unable to communicate effectively. Therefore, we designed a study (a) to determine the inter-rater reliability of the Numerical Rating Scale (NRS) and the Behavioral Pain Scale (BPS), (b) to compare pain scores of different observers and the patient, and (c) to compare NRS, BPS, and the Visual Analog Scale (VAS) for measuring pain in patients in the ICU. Methods: We performed a prospective observational study in 113 non-paralyzed critically ill patients. The attending nurses, two researchers, and the patient (when possible) obtained 371 independent observation series of NRS, BPS, and VAS. Data analyses were performed on the sample size of patients (n = 113). Results: Inter-rater reliability of the NRS and BPS proved to be adequate (kappa = 0.71 and 0.67, respectively). The level of agreement within one scale point between NRS rated by the patient and NRS scored by attending nurses was 73%. However, high patient scores (NRS ≥4) were underestimated by nurses (patients 33% versus nurses 18%). In responsive patients, a high correlation between NRS and VAS was found (rs= 0.84, P < 0.001). In ventilated patients, a moderate positive correlation was found between the NRS and the BPS (rs= 0.55, P < 0.001). However, whereas 6% of the observations were NRS of greater than or equal to 4, BPS scores were all very low (median 3.0, range 3.0 to 5.0). Conclusion: The different scales show a high reliability, but observer-based evaluation often underestimates the pain, particularly in the case of high NRS values (≥4) rated by the patient. Therefore, whenever this is possible, ICU patients should rate their pain. In unresponsive patients, primarily the attending nurse involved in daily care should score the patient's pain. In ventilated patients, the BPS should be used only in conjunction with the NRS nurse to measure pain levels in the absence of painful stimuli.

Comparing treatment effects after adjustment with multivariable Cox proportional hazards regression and propensity score methods (Article)

2008-01-01T00:00:00Z

Purpose: To compare adjusted effects of drug treatment for hypertension on the risk of stroke from propensity score (PS) methods with a multivariable Cox proportional hazards (Cox PH) regression in an observational study with censored data. Methods: From two prospective population-based cohort studies in The Netherlands a selection of subjects was used who either received drug treatment for hypertension (n = 1293) or were untreated 'candidates' for treatment (n = 954). A multivariable Cox PH was performed on the risk of stroke using eight covariates along with three PS methods. Results: In multivariable Cox PH regression the adjusted hazard ratio (HR) for treatment was 0.64 (CI95%: 0.42, 0.98). After stratification on the PS the HR was 0.58 (CI95%: 0.38, 0.89). Matching on the PS yielded a HR of 0.49 (CI95%: 0.27, 0.88), whereas adjustment with a continuous PS gave similar results as Cox regression. When more covariates were added (not possible in multivariable Cox model) a similar reduction in HR was reached by all PS methods. The inclusion of a simulated balanced covariate gave largest changes in HR using the multivariable Cox model and matching on the PS. Conclusions: In PS methods in general a larger number of confounders can be used. In this data set matching on the PS is sensitive to small changes in the model, probably because of the small number of events. Stratification, and covariate adjustment, were less sensitive to the inclusion of a non-confounder than multivariable Cox PH regression. Attention should be paid to PS model building and balance checking. Copyright

Diuretic-gene interaction and the risk of myocardial infarction and stroke (Article)

2007-10-01T00:00:00Z

This study investigates whether the interaction between diuretics and alpha-adducin (ADD1) G460W or G-protein β3-subunit (GNB3) rs2301339 polymorphism modifies the risk of myocardial infarction (MI) or stroke. Data were used from the Rotterdam Study. The drug-gene interaction was determined with a Cox proportional hazard model with adjustment for each drug class as time-dependent covariates. The risk of MI in current users of low-ceiling diuretics with one or two copies of the ADD1 W-allele (hazard ration (HR)=0.92) was similar compared to the expected joint effect of the W-allele and low-ceiling diuretics on a multiplicative scale (1.04 × 0.90=0.94) (synergy index (SI):0.99; 95% confidence interval (CI): 0.43-2.27). No drug-gene interaction was found on the risk of stroke (SI:0.66; 95% CI:0.43-1.27). In addition, a trend towards an interaction was found between current use and the GNB3 rs230119 G/A polymorphism on the risk of MI (SI: 0.51; 95% CI: 0.23-1.15), whereas no interaction on the risk of stroke was found (SI: 0.84; 95% CI: 0.46-1.56).

Angiotensinogen M235T polymorphism and the risk of myocardial infarction and stroke among hypertensive patients on ACE-inhibitors or β-blockers (Article)

2007-04-01T00:00:00Z

Angiotensinogen is an essential component of the renin-angiotensin system. ACE-inhibitors and β-blockers both have a direct influence on this system. To investigate whether the association between use of ACE-inhibitors or β-blockers and the risk of myocardial infarction (MI) or stroke is modified by the T-allele of the angiotensinogen M235T polymorphism. In this study, 4097 subjects with hypertension, aged 55 years and older, were included from the Rotterdam Study, a population-based prospective cohort study in the Netherlands, from July 1, 1991 onwards. Follow-up ended at the diagnosis date of MI, stroke, death, or the end of the study period (January 1, 2002). The drug-gene interaction on the risk of MI or stroke was determined with a Cox proportional hazard model with adjustments for each drug class as time-dependent covariates. The risk of MI was increased in current use of ACE-inhibitors with the MT or TT genotype compared to ACE-inhibitors with the MM genotype (Synergy Index (SI): 4.00; 95% CI: 1.32-12.11). A significant drug-gene interaction was not found on the risk of stroke (SI: 1.83; 95% CI: 0.95-3.54) in ACE-inhibitor users or between current use of β-blockers and the AGT M235T polymorphism on the risk of MI or stroke. ACE-inhibitor users with at least one copy of the 235T-allele of the AGT gene might have an increased risk of MI and stroke.

Adherence to and dosing of beta-hydroxy-beta-methylglutaryl coenzyme a reductase inhibitors in the general population differs according to apolipoprotein E-genotypes (Article)

2003-01-01T00:00:00Z

Discontinuation and poor adherence to therapy are major problems during long-term treatment, particularly with cholesterol lowering drugs. Several studies have indicated that the cholesterol lowering effect of statins differs according to apolipoprotein (apo)E genotypes. Low-density lipoprotein-cholesterol lowering capacity appears to be smaller in subjects with the epsilon(4) allele. To assess whether the use of statins in daily practice differs according to apoE genotypes, we used data from the Rotterdam Study, a population-based prospective cohort study in the Netherlands, which started in 1990 and included 7983 subjects aged 55 years or more. During follow-up, there were 798 subjects who started to use statins. We used a Cox proportional hazard model to determine the rate of discontinuation in the first 3 years of statin use. Subjects on statin therapy with epsilon(2)epsilon(2) and epsilon(4)epsilon(4) genotypes showed a trend towards higher dosages than subjects with the other genotypes. Relative to subjects with the epsilon(2)epsilon(3) genotype, those with the epsilon(4)epsilon(4) genotype had a risk of 2.28 [95% confidence interval (CI) 1.02-5.12] to discontinue statins within 3 years. In women, this relative risk was 1.70 (CI 0.53-5.42) versus 3.18 (CI 1.01-10.03) in men. The apoE genotype is associated with discontinuation of statins. This suggests that subjects who are genetically prone to develop hypercholesterolemia show the highest risk of discontinuation of treatment.