Daniel H Simon, Andrea M Tilstra and Ryan K Masters
Rising mortality among young and middle-aged White Americans has alarmed researchers, public health professionals and the broader public. These concerns were amplified by a 2015 study in which the authors attributed rising mortality rates among White Americans to increases in deaths from chronic liver disease, suicide and drug overdoses. The authors argued that increased mortality from these causes of death is likely a result of the “same underlying epidemic” that is affecting a “lost generation” of Americans. The underlying epidemic was said to be “deaths of despair”, originating from rising distress, economic insecurity and chronic pain.
Only a few years ago, doctors would advise their patients that elevated blood levels of high-density lipoprotein cholesterol (HDL-C), then termed the “good cholesterol”, were beneficial and would protect them against coronary heart disease. This belief has been called into question, however, as neither genetics nor clinical trials could demonstrate that raising HDL-C levels would protect against cardiovascular disease. Our study, published recently in the IJE, casts further doubt on this “not-so-good-anymore” cholesterol by showing that genetic variants that cause higher HDL-C levels also increase the risk for age-related macular degeneration (AMD).
Tanja AJ Houweling, David Osrin, Kishwar Azad, Dharma S Manandhar, Prasanta Tripathy, Tambosi Phiri, Joanna Morrison and Anthony Costello
In low- and middle-income countries, the odds of surviving the first 28 days of life are grossly unequal between infants born in deprived and better-off families, even among children living in the same community. In our study, recently published in the IJE, we have shown that women’s groups are able to address this problem. Under the guidance of a facilitator, women came together every month to discuss problems during pregnancy, delivery and the newborn period, and then designed and implemented strategies to overcome these problems with the help of the entire community.
Eleonora Uphoff, Neil Small, Rosie McEachan and Kate Pickett
For some years, our research has been based in the city of Bradford in northern England. We are often asked to justify our research setting. There seems to be a concern that a cohort population that is not representative of the nation as a whole or of the ‘average person’ cannot produce valuable insights beyond its local setting.
While such concerns are not new, they now seem more present, perhaps due to the rise of Big Data or the increased sharing of and access to data from national surveys and cohorts. Do these reservations represent a push for representativeness and generalisability in epidemiology? If so, this might come at the expense of research aiming to paint a more detailed picture of population health.
Vicente Martínez-Vizcaíno, Celia Álvarez-Bueno and Iván Cavero-Redondo
Our study, recently published in the IJE, looks at the relationship between pre-gestational weight status and children’s neurodevelopment. It shows that children born to mothers who were normal weight before pregnancy scored better on cognition tests than children born to obese women. An original aspect of our study is that it summarises the evidence provided by 15 previous follow-up studies, including samples from seven different countries, and provides information for both cognition tests and general intelligence scores.
Vicky Stiles, Brad Metcalf, Karen Knapp and Alex Rowlands
We don’t yet know whether it’s best to do it all at once, or little and often, but what we do know is that if a woman’s day-to-day activity contains 1–2 minutes of weight-bearing, high-intensity activity, similar to a medium-paced run for pre-menopausal women or a slow jog for post-menopausal women, she will have better bone health than women who do less. The benefits of high-impact activity on bone health are nothing new. What is novel about our findings is that better bone health is linked to such a short amount of daily activity, albeit at an intensity of the running variety.
Maria Melchior, Laura Pryor and Marie Jauffret-Roustide
Our study, recently published in the IJE, shows that youths who initiate cannabis use before the age of 17 years are 60% less likely to pursue higher education than those who never used cannabis. An original aspect of our study, which was based on data from the longitudinal TEMPO cohort in France, is that we were able to take into account youths’ psychological and school difficulties in childhood and adolescence, as well as their parents’ characteristics.
In recent decades, cannabis use has become frequent among youths growing up in Europe, North America and Australasia. The potential health effects of cannabis use include reductions in memory and concentration. Because the brain is thought to develop until the age of 25, adolescent substance use could have lasting negative effects on executive functions, which can in turn result in school difficulties and low educational achievement.
Alberto J. Alaniz, Antonella Bacigalupo and Pedro E. Cattan
Our study, published recently in the IJE, shows that 43.9% of the world population — about three billion people — are exposed to Zika virus, due to the probability of presence of its vector: the mosquito Aedes aegypti.
Zika virus has become an important public health problem worldwide. In 2016, the World Health Organization released a global alert in response to the risk of this virus to the population. The pathogen is especially aggressive in pregnant women, because it has been associated with microcephaly in the fetus. On the other hand, it causes different clinical manifestations in adults, such as mild fever, rash, headache and joint pain. In some countries the alert was very restrictive, even going so far as to contemplate birth control programs to avoid the infection of pregnant women.
Arguments about causal inference in ‘modern epidemiology’ revolve around the ways in which causes can and should be defined. The potential outcomes approach, a formalized kind of counterfactual reasoning, often aided by directed acyclic graphs (DAGs), can be seen as too rigid and too far removed from many of the complex ‘dirty’ problems of social epidemiology, such as social inequalities and racism. If a potential ‘cause’ cannot be manipulated is it sensible to disregard it, relegating it to the ‘not suitable for epidemiology’ category? The use of properly constructed DAGs may aid causal thinking and help plan relevant analyses – Neil Pearce and Debbie Lawlor provide a simple, but excellent discussion of the use of DAGs in their essay review of Causal Inference in Statistics: A Primer by Judea Pearl and colleagues. However, increasingly, DAGs and analyses are constructed by computer programs, such as DAGitty, now available as an R package ‘dagitty’. Useful as such programmes are, the temptation to use evaluations of DAG-dataset inconsistency to generate purely data-driven, post-hoc modifications to DAGs, raises concern about overfitting and biased inference. Continue reading “Causality in Epidemiology – Themed issue”→