Background. Patients with chronic kidney disease (CKD) are at a higher risk of major adverse cardiovascular events (MACE) compared with the general population, but gender differences in this risk,... Show moreBackground. Patients with chronic kidney disease (CKD) are at a higher risk of major adverse cardiovascular events (MACE) compared with the general population, but gender differences in this risk, especially in older adults, are not fully known. We aim to identify gender differences in the risk of MACE in older European CKD patients, and explore factors that may explain these differences.Methods. The European Quality study (EQUAL) is a prospective study on stage 4-5 CKD patients, >= 65 years old, not on dialysis, from Germany, Italy, the Netherlands, Poland, Sweden and the UK. Cox regression and cumulative incidence competing risk curves were used to identify gender differences in MACE risks. Mediation analysis was used to identify variables which may explain risk differences between men and women.Results. A total of 417 men out of 1134 (37%) and 185 women out of 602 women (31%) experienced at least one MACE, over a follow-up period of 5 years. Women had an 18% lower risk of first MACE compared with men (hazard ratio 0.82; 95% confidence interval 0.69-0.97; P =.02), which was attenuated after adjusting for pre-existing cardiometabolic comorbidities and cardiovascular risk factors. There were no significant gender differences in the risk of recurrent MACE or fatal MACE. The risk difference in MACE by gender was larger in patients aged 65-75 years, compared with patients over 75 years.Conclusions. In a cohort of older adults with advanced CKD, women had lower risks of MACE. These risk differences were partially explained by pre-existing cardiometabolic comorbidities and cardiovascular risk factors.[GRAPHICS]. Show less
Background The aim of this study was to identify trends in total, deceased donor (DD) and living donor (LD) kidney transplantation (KT) rates in European countries. Methods The European Renal... Show moreBackground The aim of this study was to identify trends in total, deceased donor (DD) and living donor (LD) kidney transplantation (KT) rates in European countries. Methods The European Renal Association (ERA) Registry and the Global Observatory on Donation and Transplantation (GODT) databases were used to obtain the number of KTs in individual European countries between 2010 and 2018. General population counts were obtained from Eurostat or the national bureaus of statistics. The KT rate per million population (p.m.p.) and the average annual percentage change (APC) were calculated. Results The total KT rate in the 40 participating countries increased with 1.9% annually [95% confidence interval (CI) 1.5, 2.2] from 29.6 p.m.p. in 2010 to 34.7 p.m.p. in 2018, reflecting an increase of 3.4 p.m.p. in the DD-KT rate (from 21.6 p.m.p. to 25.0 p.m.p.; APC 1.9%; 95% CI 1.3, 2.4) and of 1.5 p.m.p. in the LD-KT rate (from 8.1 p.m.p. to 9.6 p.m.p.; APC 1.6%; 95% CI 1.0, 2.3). The trends in KT rate varied widely across European countries. An East-West gradient was observed for DD-KT rate, with Western European countries performing more KTs. In addition, most countries performed fewer LD-KTs. In 2018, Spain had the highest DD-KT rate (64.6 p.m.p.) and Turkey the highest LD-KT rate (37.0 p.m.p.). Conclusions The total KT rate increased due to a rise in the KT rate from DDs and to a lesser extent from LDs, with large differences between individual European countries. Show less
Epidemiological studies often aim to investigate the causal contribution of a risk factor to a disease or other outcome. In etiological research, one is usually interested in the (biological)... Show moreEpidemiological studies often aim to investigate the causal contribution of a risk factor to a disease or other outcome. In etiological research, one is usually interested in the (biological) mechanism(s) underlying the studied relationship. Inappropriate conduct of an etiological study may have major implications for the correctness of the results and interpretation of the findings. Therefore, in this paper, we aim to describe step by step how etiological research should be carried out, together with its common pitfalls. These steps involve finding and formulating a well-defined etiological research question, choosing an appropriate study design including a suitable comparison group, adequate modelling, and adequate reporting and interpretation of the results. Show less
Roumeliotis, S.; Abd ElHafeez, S.; Jager, K.J.; Dekker, F.W.; Stel, V.S.; Pitino, A.; ... ; Tripepi, G. 2021
Ecological studies are observational studies commonly used in public health research. The main characteristic of this study design is that the statistical analysis is based on pooled (i.e.,... Show moreEcological studies are observational studies commonly used in public health research. The main characteristic of this study design is that the statistical analysis is based on pooled (i.e., aggregated) rather than on individual data. Thus, patient-level information such as age, gender, income and disease condition are not considered as individual characteristics but as mean values or frequencies, calculated at country or community level. Ecological studies can be used to compare the aggregated prevalence and incidence data of a given condition across different geographical areas, to assess time-related trends of the frequency of a pre-defined disease/condition, to identify factors explaining changes in health indicators over time in specific populations, to discriminate genetic from environmental causes of geographical variation in disease, or to investigate the relationship between a population-level exposure and a specific disease or condition. The major pitfall in ecological studies is the ecological fallacy, a bias which occurs when conclusions about individuals are erroneously deduced from results about the group to which those individuals belong. In this paper, by using a series of examples, we provide a general explanation of the ecological studies and provide some useful elements to recognize or suspect ecological fallacy in this type of studies. Show less
In evidence-based medicine, clinical research questions may be addressed by different study designs. This article describes when randomized controlled trials (RCT) are needed and when observational... Show moreIn evidence-based medicine, clinical research questions may be addressed by different study designs. This article describes when randomized controlled trials (RCT) are needed and when observational studies are more suitable. According to the Centre for Evidence-Based Medicine, study designs can be divided into analytic and non-analytic (descriptive) study designs. Analytic studies aim to quantify the association of an intervention (eg, treatment) or a naturally occurring exposure with an outcome. They can be subdivided into experimental (ie, RCT) and observational studies. The RCT is the best study design to evaluate theintendedeffect of an intervention, because the randomization procedure breaks the link between the allocation of the intervention and patient prognosis. If the randomization of the intervention or exposure is not possible, one needs to depend on observational analytic studies, but these studies usually suffer from bias and confounding. If the study focuses onunintendedeffects of interventions (ie, effects of an intervention that are not intended or foreseen), observational analytic studies are the most suitable study designs, provided that there is no link between the allocation of the intervention and the unintended effect. Furthermore, non-analytic studies (ie, descriptive studies) also rely on observational study designs. In summary, RCTs and observational study designs are inherently different, and depending on the study aim, they each have their own strengths and weaknesses. Show less
Study quality depends on a number of factors, one of them being internal validity. Such validity can be affected by random and systematic error, the latter also known as bias. Both make it more... Show moreStudy quality depends on a number of factors, one of them being internal validity. Such validity can be affected by random and systematic error, the latter also known as bias. Both make it more difficult to assess a correct frequency or the true relationship between exposure and outcome. Where random error can be addressed by increasing the sample size, a systematic error in the design, the conduct or the reporting of a study is more problematic. In this article, we will focus on bias, discuss different types of selection bias (sampling bias, confounding by indication, incidence-prevalence bias, attrition bias, collider stratification bias and publication bias) and information bias (recall bias, interviewer bias, observer bias and lead-time bias), indicate the type of studies where they most frequently occur and provide suggestions for their prevention. Show less
Patients with chronic kidney disease (CKD) who live up to renal replacement therapy (RRT) are a selected group of patients with a high mortality risk. The aim of this paper is to contribute a... Show morePatients with chronic kidney disease (CKD) who live up to renal replacement therapy (RRT) are a selected group of patients with a high mortality risk. The aim of this paper is to contribute a potential epidemiological explanation as to why therapeutic interventions - targeting specific causes of death - of which the effectiveness has been shown in the general population may not have a similar impact in a highly selected population like RRT patients. In this perspective, selection processes over the course of renal disease progression as well as the potential 'dilution' of an effect in the presence of highly increased mortality from other causes need attention. We suggest that the results from well-conducted high-quality studies in incident RRT patients without or with only very limited in-and exclusion criteria are likely the ones best qualified to be extrapolated to other RRT populations. Show less
Background. Information on demographics and survival of patients starting renal replacement therapy (RRT) for end-stage renal disease (ESRD) due to multiple myeloma (MM) or light-chain deposit... Show moreBackground. Information on demographics and survival of patients starting renal replacement therapy (RRT) for end-stage renal disease (ESRD) due to multiple myeloma (MM) or light-chain deposit disease (LCDD) is scarce. The aim of this study was to describe the incidence, characteristics, causes of death and survival rates of RRT for ESRD due to MM or LCDD in the ERA-EDTA Registry. Methods. Thirteen national registries providing data on patients who started RRT from 1986-2005 to the ERA-EDTA Registry participated. Incidence per million population (pmp) of RRT for ESRD due to MM or LCDD and other causes (non-MM) was observed overtime. Patient survival on RRT was examined, unadjusted and adjusted for age and gender. Results. Of the 159 637 patients on RRT, 2453 (1.54%) had MM or LCDD. The incidence of RRT for ESRD due to MM or LCDD, adjusted for age and gender, increased from 0.70 pmp in 1986-1990 to 2.52 pmp in 2001-2005. MM and LCDD patients compared to non-MM patients were older and a higher percentage was on haemodialysis at day 91 after the start of RRT. The most common causes of death in MM and LCDD patients were malignancy (36.1%), cardiovascular causes (17.2%) and infection (14.7%). MM and LCDD patients had a 2.77 (95% CI, 2.65-2.90) higher risk of death compared to non-MM patients. The unadjusted median survival on RRT was 0.91 years in MM and LCDD patients and 4.46 years in nonMM patients. During follow-up, 35 patients were transplanted and their mean survival was 9.6 years. Conclusion. The incidence of RRT for ESR.D due to MM or LCDD has increased over the past 20 years in Europe. The median patient survival on RRT for MM and LCDD patients Show less
