Addressing selection bias in the UK Biobank neurological imaging cohort

The UK Biobank is a national prospective study of half a million participants between the ages of 40 and 69 at the time of recruitment between 2006 and 2010, established to facilitate research on diseases of aging. The imaging cohort is a subset of UK Biobank participants who have agreed to undergo extensive additional imaging assessments. However, Fry et al (2017) find evidence of "healthy volunteer bias" in the UK Biobank -- participants are less likely to smoke, be obese, consume alcohol daily than the target population of UK adults. Here we examine selection bias in the UK Biobank imaging cohort. We address two common misconceptions: first, that study size can compensate for bias in data collection, and second that selection bias does not affect estimates of associations, which are the primary interest of the UK Biobank. We introduce inverse probability weighting (IPW) as an approach commonly used in survey research that can be used to address selection bias in volunteer health studies like the UK Biobank. We discuss 6 such methods -- five existing and one novel --, assess relative performance in simulation studies, and apply them to the UK Biobank imaging cohort. We find that our novel method, BART for predicting the probability of selection combined with raking, performs well relative to existing methods, and helps alleviate selection bias in the UK Biobank imaging cohort.

Accessible authentication: dyslexia and password strategies

Purpose The purpose of this paper is to reveal the lived experiences of dyslexics in engaging with all kinds of alphanumeric authentication mechanisms. Design/methodology/approach A significant proportion of the world’s population experiences some degree of dyslexia, which can lead to spelling, processing, sequencing and retention difficulties. Passwords, being essentially sequences of alphanumeric characters, make it likely that dyslexics will struggle with these, even more so than the rest of the population. Here, this study explores the difficulties people with dyslexia face, their general experiences with passwords, the coping strategies they use and the advice they can provide to developers and others who struggle with passwords. This paper collects empirical data through semi-structured interviews with 13 participants. Thematic analysis was used to provide an in-depth view of each participant’s experience. Findings The main contribution of this paper is to provide evidence related to the inaccessibility dimensions of passwords as an authentication mechanism, especially for dyslexics and to recommend a solution direction. Research limitations/implications There is a possible volunteer bias, as this study is dealing with self-reported data including historical and reflective elements and this paper is seeking information only from those with self-declared or diagnosed dyslexia. Furthermore, many expressed interest or curiosity in the relationship between dyslexia and password difficulties, for some a motivation for their participation. Finally, given that the participants told us that dyslexics might hide, it is possible that the experiences of those who do hide are different from those who chose to speak to us and thus were not hiding. Originality/value A few authors have written about the difficulties dyslexics face when it comes to passwords, but no one has asked dyslexics to tell them about their experiences. This paper fills that gap.

Comparison of Dietary Intakes Between a Large Online Cohort Study (Etude NutriNet-Santé) and a Nationally Representative Cross-Sectional Study (Etude Nationale Nutrition Santé) in France: Addressing the Issue of Generalizability in E-Epidemiology

Despite some advantages over traditional methods, Web-based studies elicit concerns about generalizability. To address this issue, we compared dietary intakes between an electronic (e-) cohort study and a nationally representative survey. We studied 49,443 French volunteers aged 18–74 years recruited during 2009–2010 in the NutriNet-Santé Study, a general population-based e-cohort study. The Etude Nationale Nutrition Santé (ENNS; 2006–2007), a cross-sectional study with a nationally representative sample of 2,754 French adults aged 18–74 years, served as the reference data set. Reported dietary intakes from three 24-hour dietary records were weighted and compared between the two studies via Student t tests for mean location, using a >5% cutoff for establishing practically meaningful differences. We observed similar intakes as regards carbohydrates, total lipids, protein, and total energy. However, intakes of fruit and vegetables, fiber, vitamins B6, B9, C, D, and E, iron, and magnesium were higher in the e-cohort than in the ENNS, while intakes of alcohol and nonalcoholic beverages were lower in the e-cohort. Significant sex-specific differences were observed regarding vitamins A and B12, zinc, and potassium. True intake differences, mode effects, and volunteer bias might each contribute to explaining the findings. In the future, repeated use of the same tool in large e-cohorts with heterogeneous dietary exposures could serve research purposes and supplement group-level monitoring of dietary trends.

Volunteer Bias in Research on Friendship Among Emerging Adults

Five studies ( N = 5,150) relying on an exhaustive procedure addressed whether volunteer bias (VB) exists in friendship research among emerging adults (EAs). Consistently, the studies showed that women are more willing than men to participate in research on same-sex best friendship (SSBF). Studies 2 through 5 showed that friendship duration is not related to volunteering. Studies 3 and 4 showed that the friendships of volunteers were higher in positive friendship experiences compared to nonvolunteers. Finally, Study 5 showed that a significant portion of nonvolunteers ended up participating in research on SSBF. VB in research on friendship is an artifact that presents a concern for the generalizability and validity of findings relative to the friendship experiences of EAs. Recruitment strategies that could alleviate this problem are discussed.