Engelfriet, P.M.

Estimating net transition probabilities from cross-sectional data with application to risk factors in chronic disease modeling (Article)

2012-03-15T00:00:00Z

A problem occurring in chronic disease modeling is the estimation of transition probabilities of moving from one state of a categorical risk factor to another. Transitions could be obtained from a cohort study, but often such data may not be available. However, under the assumption that transitions remain stable over time, age specific cross-sectional prevalence data could be used instead. Problems that then arise are parameter identifiability and the fact that age dependent cross-sectional data are often noisy or are given in age intervals. In this paper we propose a method to estimate so-called net annual transition probabilities from cross-sectional data, including their uncertainties. Net transitions only describe the net inflow or outflow into a certain risk factor state at a certain age. Our approach consists of two steps: first, smooth the data using multinomial P-splines, second, from these data estimate net transition probabilities. This second step can be formulated as a transportation problem, which is solved using the simplex algorithm from linear programming theory. A sensible specification of the cost matrix is crucial to get meaningful results. Uncertainties are assessed by parametric bootstrapping. We illustrate our method using data on body mass index. We conclude that this method provides a flexible way of estimating net transitions and that the use of net transitions has implications for model dynamics, for example when modeling interventions.

Co-occurrence of diabetes, myocardial infarction, stroke, and cancer: Quantifying age patterns in the Dutch population using health survey data (Article)

2011-09-01T00:00:00Z

Background: The high prevalence of chronic diseases in Western countries implies that the presence of multiple chronic diseases within one person is common. Especially at older ages, when the likelihood of having a chronic disease increases, the co-occurrence of distinct diseases will be encountered more frequently. The aim of this study was to estimate the age-specific prevalence of multimorbidity in the general population. In particular, we investigate to what extent specific pairs of diseases cluster within people and how this deviates from what is to be expected under the assumption of the independent occurrence of diseases (i.e., sheer coincidence).Methods: We used data from a Dutch health survey to estimate the prevalence of pairs of chronic diseases specified by age. Diseases we focused on were diabetes, myocardial infarction, stroke, and cancer. Multinomial P-splines were fitted to the data to model the relation between age and disease status (single versus two diseases). To assess to what extent co-occurrence cannot be explained by independent occurrence, we estimated observed/expected co-occurrence ratios using predictions of the fitted regression models.Results: Prevalence increased with age for all disease pairs. For all disease pairs, prevalence at most ages was much higher than is to be expected on the basis of coincidence. Observed/expected ratios of disease combinations decreased with age.Conclusion: Common chronic diseases co-occur in one individual more frequently than is due to chance. In monitoring the occurrence of diseases among the population at large, such multimorbidity is insufficiently taken into account.

To die with or from heart failure: A difference that counts (Article)

2011-04-01T00:00:00Z

AimsMortality attributed to a disease is an important public health measure of the 'burden' of that disease. A discrepancy has been noted between the high mortality rates associated with heart failure (HF) and the share of deaths ascribed to HF in official mortality statistics. It was our main aim to estimate excess mortality associated with HF and use the estimates to better understand the burden of HF.Methods and resultsExcess mortality was defined as the difference in mortality rates between individuals with and those without HF. An epidemiological model was formulated that allowed deriving age-specific excess mortality rates in HF patients from HF incidence and prevalence. Incidence and prevalence were estimated from yearly collected cross-sectional data from four nationally representative General Practice registries in the Netherlands. The year 2007 was chosen as a reference. Next, excess mortality rates were used to calculate numbers of deaths among HF patients and compare the figures with national cause-of-death statistics. The latter were found to be more than three times smaller than the former (roughly 6000 vs. 21 000). Further, by applying HF prevalence and mortality rates to a life table of the Dutch population, average numbers of life years lost due to HF were calculated to be 6.9 years.ConclusionNational mortality statistics strongly underestimate the number of deaths associated with HF. Moreover, the high mortality rate in HF patients amounts to a remarkably large number of life years lost given the advanced age of disease onset.

Estimating and comparing incidence and prevalence of chronic diseases by combining GP registry data: The role of uncertainty (Article)

2011-03-17T00:00:00Z

Background: Estimates of disease incidence and prevalence are core indicators of public health. The manner in which these indicators stand out against each other provide guidance as to which diseases are most common and what health problems deserve priority. Our aim was to investigate how routinely collected data from different general practitioner registration networks (GPRNs) can be combined to estimate incidence and prevalence of chronic diseases and to explore the role of uncertainty when comparing diseases. Methods. Incidence and prevalence counts, specified by gender and age, of 18 chronic diseases from 5 GPRNs in the Netherlands from the year 2007 were used as input. Generalized linear mixed models were fitted with the GPRN identifier acting as random intercept, and age and gender as explanatory variables. Using predictions of the regression models we estimated the incidence and prevalence for 18 chronic diseases and calculated a stochastic ranking of diseases in terms of incidence and prevalence per 1,000. Results: Incidence was highest for coronary heart disease and prevalence was highest for diabetes if we looked at the point estimates. The between GPRN variance in general was higher for incidence than for prevalence. Since uncertainty intervals were wide for some diseases and overlapped, the ranking of diseases was subject to uncertainty. For incidence shifts in rank of up to twelve positions were observed. For prevalence, most diseases shifted maximally three or four places in rank. Conclusion: Estimates of incidence and prevalence can be obtained by combining data from GPRNs. Uncertainty in the estimates of absolute figures may lead to different rankings of diseases and, hence, should be taken into consideration when comparing disease incidences and prevalences.

Indirect Estimation of Chronic Disease Excess Mortality (Letter To Editor)

2010-05-01T00:00:00Z

Smoking and its effects on mortality in adults with congenital heart disease (Article)

2008-06-23T00:00:00Z

Aims: To describe smoking habits in adults with congenital heart disease (ACHD) and to assess the relationship between smoking exposure and cardiovascular mortality. Methods: Data on smoking history and cardiovascular mortality were extracted from the Euro Heart Survey on adult congenital heart disease - a retrospective cohort study, that included patients diagnosed with 1 of 8 subgroups of ACHD (Atrial Septal Defects, Ventricular Septal Defects, Marfan Syndrome, Aortic Coarctation, Tetralogy of Fallot (ToF), Transposition of the Great Arteries (TGA), Fontan circulation, and Cyanotic disease). Results: Complete data of 3375 ACHD patients (median age 28 years) were available for analysis. At inclusion, 9.3% (n = 314) were current smokers and 4.2% (n = 142) of the patients had smoked in the past. During a median follow-up of 5.1 years, 101 patients (3%) died. In the majority of cases the cause of death was cardiovascular (n = 81; 80%). Kaplan-Meier and Cox survival analysis for each of the defects separately showed a significantly increased age and sex-adjusted cardiovascular mortality associated with smoking exposure in TGA patients (Hazard ratio 4.2 (95% CI 1.0-16.8); P = 0.044). Also in ToF mortality was higher amongst smokers, though not significantly (HR 3.4 (95% CI 0.6-18.5); P = 0.15). In the remaining defects no relationship between smoking and cardiovascular mortality was observed. Conclusion: The prevalence of smoking amongst ACHD patients is relatively low. Smoking exposure is associated with increased cardiovascular mortality in patients with TGA. Prospective long-term follow-up studies are necessary.

Repaired and open atrial septal defects type II in adulthood: An epidemiological study of a large European cohort (Article)

2008-06-06T00:00:00Z

Background: There is a lack of evidence regarding treatment options for adults with an atrial septal defect (ASD) who present with an open defect or with sequelae after closure of the defect. The aim of this study was to describe the clinical characteristics and treatment of a large cohort of adult patients born with an ASD type II. Methods and results: Data on the clinical characteristics of 882 ASD II patients (mean follow-up of 4.2 years) included in the Euro Heart Survey on adult congenital heart disease were analysed. At baseline, the defects of 377 patients (mean age 39.2 (16.1) years; 65% females) had been closed, leaving 505 patients (mean age 41.1 (16.4) years; 68% females) with an open ASD. Hemodynamic abnormalities were more prevalent among patients with an open compared to those with a closed defect at baseline: pulmonary arterial hypertension 35% versus13%; right ventricular (RV) dysfunction 31% versus 8%; and severe RV volume overload 18% versus 1% (all P-values < 0.001). These prevalences increased with age, but hemodynamic parameters remained stable during follow-up in nearly all patients with a small defect. Also functional limitations were more common in those with open defects at baseline compared to those with closed defects (54% versus 25%). There was no difference in the prevalence of arrhythmia's. The best independent predictors of functional limitations appeared to be PAH (odds ratio 25.2 (5.8-109.6); P < 0.001)) and RV volume overload (odds ratio 2.3 (1.5-3.4; P < 0.001)) in a multivariable model. During follow-up, 9 patients died and in 294 patients the defect was closed, in 180 patients surgically, and in 114 patients by device. Among the latter group there were relatively more females (78% vs 66%; P = 0.035). In the surgically closed group defects were more "severe". There were substantial differences according to country in the relative frequency of device closure versus surgical closure, as well as the size and hemodynamic severity of the defects closed. Conclusion: The data from this study provide a cross-section of the kind of adult patients with an ASD that are seen at outpatient clinics for adult congenital heart disease throughout Europe. Taken together, non-operated patients fared significantly worse in all aspects of hemodynamics studied than the patients whose defects had been closed. In moderate or large defects, when not-operated, clinical parameters tend to worsen with time, and closure of such a defect-the sooner the better-seems always to be the preferred treatment option. In the majority of small defects, operation is not necessarily indicated.

Pulmonary arterial hypertension in adults born with a heart septal defect: The Euro Heart Survey on adult congenital heart disease (Article)

2007-06-01T00:00:00Z

Aim: To investigate the role of pulmonary arterial hypertension (PAH) in adult patients born with a cardiac septal defect, by assessing its prevalence and its relation with patient characteristics and outcome. Methods and results: From the database of the Euro Heart Survey on adult congenital heart disease (a retrospective cohort study with a 5-year follow-up), the relevant data on all 1877 patients with an atrial septal defect (ASD), a ventricular septal defect (VSD), or a cyanotic defect were analysed. Most patients (83%) attended a specialised centre. There were 896 patients with an ASD (377 closed, 504 open without and 15 with Eisenmenger's syndrome), 710 with a VSD (275, 352 and 83, respectively), 133 with Eisenmenger's syndrome owing to another defect and 138 remaining patients with cyanosis. PAH was present in 531 (28%) patients, or in 34% of patients with an open ASD and 28% of patients with an open VSD, and 12% and 13% of patients with a closed defect, respectively. Mortality was highest in patients with Eisenmenger's syndrome (20.6%). In case of an open defect, PAH entailed an eightfold increased probability of functional limitations (New York Heart Association class > 1), with a further sixfold increase when Eisenmenger's syndrome was present. Also, in patients with persisting PAH despite defect closure, functional limitations were more common. In patients with ASD, the prevalence of right ventricular dysfunction increased with systolic pulmonary artery pressure (OR= 1.073 per mm Hg; p<0.001). Major bleeding events were more prevalent in patients with cyanosis with than without Eisenmenger's syndrome (17% vs 3%; p<0.001). Conclusion: In this selected population of adults with congenital heart disease, PAH was common and predisposed to more symptoms and further clinical deterioration, even among patients with previous defect closure and patients who had not developed Eisenmenger's physiology.