A structured approach to hypotheses involving continuous exposures over the life course

© The Author 2016. Published by Oxford University Press on behalf of the International Epidemiological Association. Background: Epidemiologists are often interested in examining different hypotheses for how exposures measured repeatedly over the life course relate to later-life outcomes. A structured approach for selecting the hypotheses most supported by theory and observed data has been developed for binary exposures. The aim of this paper is to extend this to include continuous exposures and allow for confounding and missing data. Methods: We studied two examples, the association between: (i) maternal weight during pregnancy and birthweight; and (ii) stressful family events throughout childhood and depression in adolescence. In each example we considered several plausible hypotheses including accumulation, critical periods, sensitive periods, change and effect modification. We used least angle regression to select the hypothesis that explained the most variation in the outcome, demonstrating appropriate methods for adjusting for confounders and dealing with missing data. Results: The structured approach identified a combination of sensitive periods: pre-pregnancy weight, and gestational weight gain 0-20 weeks and 20-40 weeks, as the best explanation for variation in birthweight after adjusting for maternal height. A sensitive period hypothesis best explained variation in adolescent depression, with the association strengthening with the proximity of stressful family events. For each example, these models have theoretical support at least as strong as any competing hypothesis. Conclusions: We have extended the structured approach to incorporate continuous exposures, confounding and missing data. This approach can be used in either an exploratory or a confirmatory setting. The interpretation, plausibility and consistency with causal assumptions should all be considered when proposing and choosing life course hypotheses

Childhood conduct disorder trajectories, prior risk factors and cannabis use at age 16: birth cohort study

Aims: To investigate prevalence of cannabis use and problem use in boys and girls at age 16 years and to investigate the role of adversity in early life and of conduct disorder between the ages of 4 and 13 years as risk factors for these outcomes. Design: Birth cohort study Setting: England. Participants: 4159 (2393 girls) participants in the ALSPAC birth cohort providing information on cannabis use at age 16. Measurements: Cannabis use and problem cannabis use at age 16 were assessed by postal questionnaire. Material adversity, maternal substance use, maternal mental health and child conduct disorder were all assessed by maternal report. Findings: Cannabis use was more common amongst girls than boys (21.4% vs 18.3%, p=0.005). Problem cannabis use was more common in boys than girls (3.6% vs 2.8%, p=0.007). Early Onset Persistent conduct problems were strongly associated with problem cannabis use (OR 6.46 95% CI 4.06-10.28). Residence in subsidised housing (OR 3.10 95% CI 1.95, 4.92); maternal cannabis use (OR 8.84 95% CI 5.64-13.9) and maternal smoking 20 or more cigarettes per day (OR 3.28 95% CI 1.85-5.82) all predicted problem cannabis use. Attributable risks for adolescent problem cannabis use associated with the above factors were 25%, 13%, 17% and 24% respectively. Conclusions: Maternal smoking and cannabis use, early material disadvantage and early onset persistent conduct problems are important risk factors for adolescent problem cannabis use. This may have implications for prevention

The association between constipation and lower urinary tract symptoms in parous middle-aged women:a prospective cohort study

Objective: To examine the prospective association between constipation and risk of developing lower urinary tract symptoms (LUTS) in parous middle-aged women. Materials and Methods: The study uses data from 3,729 women from the Avon Longitudinal Study of Parents and Children who provided self-reports of medication intake for constipation at two time points (Baseline): 2001–2003 and 2003–2005. Women with LUTS at baseline were excluded. After 10 years of follow-up, women provided self-reports of LUTS using an adapted version of the International Consultation on Incontinence Questionnaire on Female LUTS. LUTS were categorized according to International Continence Society definitions as stress urinary incontinence (UI), urgency UI, mixed UI, nocturia, increased daytime frequency, urgency, hesitancy, and intermittency. LUTS were considered present if symptoms were reported to occur at least “sometimes” for all subtypes, except for increased daytime frequency (≥9 times) and nocturia (≥2 times nightly). Results: At follow-up, the prevalence of any LUTS was 40%. Women (mean age 43.3 years, standard deviation 0.5), who took medication for constipation at either time point had increased risks of urgency (adjusted relative risks [RRs] = 1.35; 95% confidence interval [CI] 1.04–1.95) and hesitancy (adjusted RR = 1.72; 95% CI 1.04–3.01) compared with women who reported not using medication for constipation at either time point. The risk of urgency (adjusted RR = 1.94; 95% CI 1.15–3.29) and hesitancy (adjusted RR = 1.78; 95% CI 1.03–4.19) was greater for women who reported taking medication for constipation at both time points. There was no evidence that constipation was associated with stress UI, urgency UI, mixed UI, nocturia, increased daytime frequency, and intermittency. Conclusion: Constipation is prospectively associated with an increased risk of urgency and hesitancy among parous middle-aged women. If further research finds evidence that this association is causal, this implies that women should seek treatment to alleviate constipation to reduce their consequent risk of developing these LUTS

Chronic Fatigue Syndrome at Age 16 Years

BACKGROUND:In the Avon Longitudinal Study of Parents and Children (ALSPAC) birth cohort, chronic disabling fatigue lasting ≥6 months affected 1.3% of 13-year-olds, was equally common in boys and girls, and became more prevalent with increasing family adversity.METHODS:ALSPAC data were used to estimate the prevalence of chronic fatigue syndrome (CFS) at age 16 years, defined by parental report of unexplained disabling fatigue lasting ≥6 months. We investigated gender and a composite 14-item family adversity index as risk factors. School absence data were obtained from the National Pupil Database. Multiple imputation was used to address bias caused by missing data.RESULTS:The prevalence of CFS was 1.86% (95% confidence interval [CI]: 1.47 to 2.24). After excluding children with high levels of depressive symptoms, the prevalence was 0.60% (95% CI: 0.37 to 0.84). Authorized school absences were much higher (mean difference: 35.6 [95% CI: 26.4 to 44.9] half-day sessions per academic year) and reported depressive symptoms were much more likely (odds ratio [OR]: 11.0 [95% CI: 5.92 to 20.4]) in children with CFS than in those without CFS. Female gender (OR: 1.95 [95% CI: 1.33 to 2.86]) and family adversity (OR: 1.20 [95% CI: 1.01 to 1.42] per unit family adversity index) were also associated with CFS.CONCLUSIONS:CFS affected 1.9% of 16-year-olds in a UK birth cohort and was positively associated with higher family adversity. Gender was a risk factor at age 16 years but not at age 13 years or in 16-year-olds without high levels of depressive symptoms.</jats:sec

Depressive symptoms at age 9-13 and chronic disabling fatigue at age 16: A longitudinal study

Introduction: We investigated whether depressive symptoms at ages 9–13 years were associated with chronic disabling fatigue (CDF) at age 16 among children in the Avon Longitudinal Study of Parents & Children (ALSPAC) birth cohort. Methods: Depressive symptoms at ages 9, 10, 11, 12, and 13 years were defined as a child- or parent-completed Short Mood and Feelings Questionnaire (SMFQ) score ≥11 (range 0–26). SMFQ score was also analysed as a continuous exposure. Chronic disabling fatigue at 16 was defined as fatigue of ≥6 months' but < 5 years’ duration which prevented school attendance or activities, for which other causes were not identified, and with a Chalder Fatigue Questionnaire score ≥19. Logistic regression was used with multiple imputation to correct for missing data bias. We performed sensitivity analyses in which children who had CDF and depressive symptoms at age 16 were reclassified as not having CDF. Results: In fully adjusted models using imputed data (N = 13,978), depressive symptoms at ages 9, 11, and 13 years were associated with 2- to 3-fold higher odds of CDF at age 16. Each one-point increase in SMFQ score at ages 9, 10, 11, 12, and 13 years was associated with 6–11% higher odds of CDF at age 16. Depressive symptoms and continuous SMFQ scores at each age were not associated with CDF if the outcome was reclassified to exclude children with comorbid depressive symptoms at age 16. Conclusions: Depressive symptoms at ages 9–13 were associated with chronic disabling fatigue at age 16, but causality is not certain

Quantitative Information Flow and Applications to Differential Privacy

International audienceSecure information flow is the problem of ensuring that the information made publicly available by a computational system does not leak information that should be kept secret. Since it is practically impossible to avoid leakage entirely, in recent years there has been a growing interest in considering the quantitative aspects of information flow, in order to measure and compare the amount of leakage. Information theory is widely regarded as a natural framework to provide firm foundations to quantitative information flow. In this notes we review the two main information-theoretic approaches that have been investigated: the one based on Shannon entropy, and the one based on Rényi min-entropy. Furthermore, we discuss some applications in the area of privacy. In particular, we consider statistical databases and the recently-proposed notion of differential privacy. Using the information-theoretic view, we discuss the bound that differential privacy induces on leakage, and the trade-off between utility and privac

Age- and puberty-dependent association between IQ score in early childhood and depressive symptoms in adolescence

BACKGROUND: Lower cognitive functioning in early childhood has been proposed as a risk factor for depression in later life but its association with depressive symptoms during adolescence has rarely been investigated. Our study examines the relationship between total intelligence quotient (IQ) score at age 8 years, and depressive symptoms at 11, 13, 14 and 17 years. METHOD: Study participants were 5250 children and adolescents from the Avon Longitudinal Study of Parents and their Children (ALSPAC), UK, for whom longitudinal data on depressive symptoms were available. IQ was assessed with the Wechsler Intelligence Scale for Children III, and self-reported depressive symptoms were measured with the Short Mood and Feelings Questionnaire (SMFQ). RESULTS: Multi-level analysis on continuous SMFQ scores showed that IQ at age 8 years was inversely associated with depressive symptoms at age 11 years, but the association changed direction by age 13 and 14 years (age-IQ interaction, p<0.0001; age squared-IQ interaction, p<0.0001) when a higher IQ score was associated with a higher risk of depressive symptoms. This change in IQ effect was also found in relation to pubertal stage (pubertal stage-IQ interaction, 0.00049<p=0.038). At age 17 years, however, sex-specific differences emerged (sex-age squared-IQ interaction, p=0.0075). Whilst the risk effect of higher childhood IQ scores for depressive symptoms declined in females, and some analyses even supported an inverse association by age 17 years, it persisted in males. CONCLUSIONS: Our results suggest that the association between cognitive ability in childhood and depressive symptoms in adolescence varies according to age and/or pubertal stage

Confronting the digital:Doing ethnography in modern organizational settings

Digital technologies pervade modern life. As a result, organizational ethnographers must contend with informants interacting in face-to-face and digitally mediated encounters (e.g., through email, Facebook Messenger, and Skype). This overlap of informants’ digital and physical interactions challenges ethnographers’ ability to demonstrate authenticity and multivocality in their accounts of contemporary organizing. Drawing on recent theorizing about the nature of digital artifacts and two cases of ethnographic fieldwork, we argue that digital artifacts afford ethnographers different modes of being co-present with research participants: digital as archive and digital as process. We offer guidelines to researchers on how to deploy these modes of co-presence in order to improve authenticity and multivocality in ethnographic studies of modern organizations. We also explore the implications for methodological concerns such as ethics, analytical choice, and reflexivity