Oral contraceptives and rheumatoid arthritis : further epidemiologic evidence for a protective effect

In Chapter I the history of the investigation is described: the literature reports that the pill would halve the incidence of rheumatoid arthritis which first drew our attention, our initial views on how to test this hypothesis by means of a case-control study, and the opportunity presented by the rheumatologic registry at the Erasmus University Rotterdam. The aim of the study is stated: to investigate whether the halving of the incidence of rheumatoid arthritis among oral-contraceptive users relative to never-users, as originally described in a follow-up study in Great Britain, would also be demonstrable in a case-control study in the Netherlands. In Chapter II the reasons for starting the investigation are elaborated. First, the relevant literature is critically reviewed. The evidence for a negative association between oral-contraceptive use and the development of rheumatoid arthritis is judged interesting, although still wanting: several objections to the validity of the inference can be formulated. Second, the phenomenon is interesting from a point of view of public health. If the pill protects against a crippling disease which is frequent in women, this might to a certain extent balance the negative aspects of its cardiovascular side-effects. Third, there is a strong biological interest. If the pill causally prevents rheumatoid arthritis, this provides another piece of the puzzle of the pathogenesis of this disease, which advances the state of our knowledge. The fourth and last reason for starting the investigation was the unique opportunity of a rheumatology registry that covers the patients of several of the major rheumatology clinics in the Netherlands

Point: incident exposures, prevalent exposures, and causal inference: does limiting studies to persons who are followed from first exposure onward damage epidemiology?

The idea that epidemiologic studies should start from first exposure onward has been advocated in the past few years. The study of incident exposures is contrasted with studies of prevalent exposures in which follow-up may commence after first exposure. The former approach is seen as a hallmark of a good study and necessary for causal inference. We argue that studying incident exposures may be necessary in some situations, but it is not always necessary and is not the preferred option in many instances. Conducting a study involves decisions as to which person-time experience should be included. Although studies of prevalent exposures involve left truncation (missingness on the left), studies of incident exposures may involve right censoring (missingness on the right) and therefore may not be able to assess the long-term effects of exposure. These considerations have consequences for studies of dynamic (open) populations that involve a mixture of prevalent and incident exposures. We argue that studies with prevalent exposures will remain a necessity for epidemiology. The purpose of this paper is to restore the balance between the emphasis on first exposure cohorts and the richness of epidemiologic information obtained when studying prevalent exposures

Case-control studies: basic concepts.

The purpose of this article is to present in elementary mathematical and statistical terms a simple way to quickly and effectively teach and understand case-control studies, as they are commonly done in dynamic populations-without using the rare disease assumption. Our focus is on case-control studies of disease incidence ('incident case-control studies'); we will not consider the situation of case-control studies of prevalent disease, which are published much less frequently

From ideas to studies: how to get ideas and sharpen them into research questions.

Where do new research questions come from? This is at best only partially taught in courses or textbooks about clinical or epidemiological research. Methods are taught under the assumption that a researcher already knows the research question and knows which methods will fit that question. Similarly, the real complexity of the thought processes that lead to a scientific undertaking is almost never described in published papers. In this paper, we first discuss how to get an idea that is worth researching. We describe sources of new ideas and how to foster a creative attitude by "cultivating your thoughts". Only a few of these ideas will make it into a study. Next, we describe how to sharpen and focus a research question so that a study becomes feasible and a valid test of the underlying idea. To do this, the idea needs to be "pruned". Pruning a research question means cutting away anything that is unnecessary, so that only the essence remains. This includes determining both the latent and the stated objectives, specific pruning questions, and the use of specific schemes to structure reasoning. After this, the following steps include preparation of a brief protocol, conduct of a pilot study, and writing a draft of the paper including draft tables. Then you are ready to carry out your research

Arguments about face masks and Covid-19 reflect broader methodologic debates within medical science.

There has perhaps been no issue as contentious in Covid-19 as face masks. The most contentious scientific debate has been between those who argue that "there is no scientific evidence", by which they mean that there are no randomized controlled trials (RCTs), versus those who argue that when the evidence is considered together, "the science supports that face coverings save lives". It used to be a 'given' that to decide whether a particular factor, either exogenous or endogenous, can cause a particular disease, and in what order of magnitude, one should consider all reasonably cogent evidence. This approach is being increasingly challenged, both scientifically and politically. The scientific challenge has come from methodologic views that focus on the randomized controlled trial (RCT) as the scientific gold standard, with priority being given, either to evidence from RCTs or to observational studies which closely mimic RCTs. The political challenge has come from various interests calling for the exclusion of epidemiological evidence from consideration by regulatory and advisory committees