Assortative mixing as a source of bias in epidemiological studies of sexually transmitted infections: the case of smoking and human papillomavirus

For studies examining risk factors of sexually transmitted infections (STIs), confounding can stem from characteristics of partners of study subjects, and persist after adjustment for the subjects’ individual-level characteristics. Two conditions that can result in confounding by the subjects’ partners are: (C1) partner choice is assortative by the risk factor examined and, (C2) sexual activity is associated with the risk factor. The objective of this paper is to illustrate the potential impact of the assortativity bias in studies examining STI risk factors, using smoking and human papillomavirus (HPV) as an example. We developed an HPV transmission-dynamic mathematical model in which we nested a cross-sectional study assessing the smoking–HPV association. In our base case, we assumed (1) no effect of smoking on HPV, and (2) conditions C1–C2 hold for smoking (based on empirical data). The assortativity bias caused an overestimation of the odds ratio (OR) in the simulated study after perfect adjustment for the subjects’ individual-level characteristics (adjusted OR 1·51 instead of 1·00). The bias was amplified by a lower basic reproductive number (R(0)), greater mixing assortativity and stronger association of smoking with sexual activity. Adjustment for characteristics of partners is needed to mitigate assortativity bias

A COMPARISON OF PRE- AND POST-OPERATIVE THREE-DIMENSIONAL HIP KINEMATICS DURING LEVEL WALKING IN PATIENTS WITH CAM FEMOROACETABULAR IMPINGEMENT

Cam femoroacetabular impingement (FAI) is an idiopathic progressive pathological condition of the hip joint characterized by an abnormal bony protuberance on the femoral head-neck junction (Beck, Leunig, Parvizi, Boutier, Wyss & Ganz, 2004). During the limits of hip range of motion (ROM), the protuberance jams into the acetabulum (Ganz, Parvizi, Beck, Leunig, Nötzli & Siebenrock, 2003), resulting in acute hip and groin pain (Beaulé, LeDuff, & Zaragoza, 2007). Impingement has also been shown to occur within normal ROM of the hip during basic tasks such as walking, reducing peak hip abduction angles as well as hip frontal and sagittal ROM (Kennedy, Lamontagne & Beaulé, 2009). Cam FAI primarily affects young and athletic males (Ganz, Parvizi, Beck, Leunig, Nötzli & Siebenrock, 2003), and is common in hockey, football, soccer, rugby, martial arts and tennis athletes (Philippon, Schenker, Briggs & Kuppersmith, 2007). Restricted hip mobility during activities requiring low ROM suggests more pronounced limitations during demanding athletic tasks. Surgical procedures have been developed to remove the bony abnormality from the femoral head-neck junction with the objective of attenuating hip pain and restoring normal hip biomechanics, enabling athletes to return to sport. The purpose of this study is to assess the clinical outcome of cam FAI corrective surgery by comapring pre-operative and post-operative three-dimensional (3-D) hip kinematics during level walking

Élevage porcin et santé publique : risque, controverse et violence non intentionnelle

Au Québec comme ailleurs, l’élevage porcin, considéré comme risqué par plusieurs, suscite questionnements et controverse. Des incertitudes scientifiques demeurent quant à ses effets sur la santé. D’où notre intention d’aborder, dans cet article, la question de l’influence de l’élevage porcin sur la santé psychologique et sociale. Une recension systématique a permis d’évaluer la pertinence et la qualité de la documentation scientifique à ce sujet. Les résultats montrent une association entre des effets sur la qualité de vie et ce type de production animale. En effet, la ferme porcine augmenterait la controverse et les clivages sociaux, et elle affecterait le sentiment d’appartenance à la communauté et au milieu. Elle constitue à ce titre un risque à la santé. Peut-on en l’occurrence parler de violence et, si oui, comment pourrait-on la prévenir ?As is the case in other provinces, swine production in Quebec, considered by many to be fraught with risk, raise questions and spark controversy. The scientific community is still uncertain about its repercussions, especially its effects on public health. Our purpose in this article is therefore to examine the psychological and social impact of swine production. A systematic survey was carried out to assess the quality and appropriateness of scientific literature on the subject. Aggregated results show that there is a link between living standards and this type of animal production. The issue of pig farms apparently stokes controversy and social division, while exerting a negative influence on the individual’s sense of belonging to a community and a specific social background. Pig farms therefore constitute a threat to human well-being and as such, they constitute a form of violence. The question is how to prevent it

Widespread Selection Across Coding and Noncoding DNA in the Pea Aphid Genome

Genome-wide patterns of diversity and selection are critical measures for understanding how evolution has shaped the genome. Yet, these population genomic estimates are available for only a limited number of model organisms. Here we focus on the population genomics of the pea aphid (Acyrthosiphon pisum). The pea aphid is an emerging model system that exhibits a range of intriguing biological traits not present in classic model systems. We performed low-coverage genome resequencing of 21 clonal pea aphid lines collected from alfalfa host plants in North America to characterize genome-wide patterns of diversity and selection. We observed an excess of low-frequency polymorphisms throughout coding and noncoding DNA, which we suggest is the result of a founding event and subsequent population expansion in North America. Most gene regions showed lower levels of Tajima’s D than synonymous sites, suggesting that the majority of the genome is not evolving neutrally but rather exhibits significant constraint. Furthermore, we used the pea aphid’s unique manner of X-chromosome inheritance to assign genomic scaffolds to either autosomes or the X chromosome. Comparing autosomal vs. X-linked sequence variation, we discovered that autosomal genes show an excess of low frequency variants indicating that purifying selection acts more efficiently on the X chromosome. Overall, our results provide a critical first step in characterizing the genetic diversity and evolutionary pressures on an aphid genome

Forward analysis of π\piN scattering with an expansion method

The $\pi$N forward scattering data are analyzed using an expansion method, where the invariant amplitudes are represented by expansions satisfying the forward dispersion relations. The experimental errors of the data are taken into account through the covariance matrix of the coefficients of the expansions in a careful error analysis. From the results, some coefficients, $c_{n0}^\pm$, of the subthreshold expansions have been calculated with proper error bars.Comment: 5 pages, 4 figures. v2: Added some references. v3: Corrected hyphenatio

Impacts of Maize Domestication and Breeding on Rhizosphere Microbial Community Recruitment from a Nutrient Depleted Agricultural Soil.

Maize domestication and breeding have resulted in drastic and well documented changes in aboveground traits, but belowground effects on root system functioning and rhizosphere microbial communities remain poorly understood, despite their critical importance for nutrient and water acquisition. We investigated the rhizosphere microbial community composition and structure of ten Zea mays accessions along an evolutionary transect (two teosinte, three inbred maize lines, and five modern maize hybrids) grown in nutrient depleted soil from a low input agricultural system. Microbial community analysis revealed significant differences in community composition between soil compartments (proximal vs. distal rhizosphere) and between plant genetic groups (teosinte, inbred, and modern hybrid). Only a small portion of the microbial community was differentially selected across plant genetic groups: 3.7% of prokaryotic community members and 4.9% of fungal community members were significantly associated with a specific plant genetic group. Indicator species analysis showed the greatest differentiation between modern hybrids and the other two plant genetic groups. Co-occurrence network analysis revealed that microbial co-occurrence patterns of the inbred maize lines' rhizosphere were significantly more similar to those of the teosintes than to the modern hybrids. Our results suggest that advances in hybrid development significantly impacted rhizosphere microbial communities and network assembly

Seabird species vary in behavioural response to drone census

This is the final version of the article. Available from the publisher via the DOI in this record.Unmanned aerial vehicles (UAVs) provide an opportunity to rapidly census wildlife in remote areas while removing some of the hazards. However, wildlife may respond negatively to the UAVs, thereby skewing counts. We surveyed four species of Arctic cliff-nesting seabirds (glaucous gull Larus hyperboreus, Iceland gull Larus glaucoides, common murre Uria aalge and thick-billed murre Uria lomvia) using a UAV and compared censusing techniques to ground photography. An average of 8.5% of murres flew off in response to the UAV, but >99% of those birds were non-breeders. We were unable to detect any impact of the UAV on breeding success of murres, except at a site where aerial predators were abundant and several birds lost their eggs to predators following UAV flights. Furthermore, we found little evidence for habituation by murres to the UAV. Most gulls flew off in response to the UAV, but returned to the nest within five minutes. Counts of gull nests and adults were similar between UAV and ground photography, however the UAV detected up to 52.4% more chicks because chicks were camouflaged and invisible to ground observers. UAVs provide a less hazardous and potentially more accurate method for surveying wildlife. We provide some simple recommendations for their use.We thank T. Leonard and the Seabird Ecological Reserves Advisory Committee for permission to work at Witless Bay, the Canadian Wildlife Service for permits to work at Newfoundland and Nunavut and the Government of Nunavut for permits to work in Nunavut. Newfoundland and Labrador Murre Fund, Bird Studies Canada and the Molson Foundation directly funded the work. An NSERC Discovery Grant, the Canada Research Chair in Arctic Ecology and Polar Continental Shelf Project also helped fund the project. We thank T. Burke, G. Sorenson, T. Lazarus and M. Guigueno for their help and J. Nakoolak for keeping us safe from bear