BackgroundParticipant drop-out occurs in all longitudinal studies, and if systematic, may lead to selection biases and erroneous conclusions being drawn from a study.AimsWe investigated whether drop out in the Avon Longitudinal Study of Parents And Children (ALSPAC) was systematic or random, and if systematic, whether it had an impact on the prediction of disruptive behaviour disorders.MethodTeacher reports of disruptive behaviour among currently participating, previously participating and never participating children aged 8 years in the ALSPAC longitudinal study were collected. Data on family factors were obtained in pregnancy. Simulations were conducted to explain the impact of selective drop-out on the strength of prediction.ResultsDrop out from the ALSPAC cohort was systematic and children who dropped out were more likely to suffer from disruptive behaviour disorder. Systematic participant drop-out according to the family variables, however, did not alter the association between family factors obtained in pregnancy and disruptive behaviour disorder at 8 years of age.ConclusionsCohort studies are prone to selective drop-out and are likely to underestimate the prevalence of psychiatric disorder. This empirical study and the simulations confirm that the validity of regression models is only marginally affected despite range restrictions after selective drop-out.
and the ALSPAC study teamObjective The objectives of this study were to examine the rates of domestic violence reported during and after pregnancy and to assess the importance of family adversity. Design Prospective longitudinal cohort study.Setting Bristol Avon, Southwest England.Population Seven thousand five hundred and ninety-one pregnant women with due dates between 1.4.91 and 31.12.92. Methods Questionnaires administered at 18 weeks of gestation and 8 weeks, 8 months, 21 months and 33 months postpartum. Main outcome measures The experience of emotional or physical cruelty by an intimate partner at each time point. Results Fewer women reported domestic violence victimisation during pregnancy than they did postpartum (18 weeks of gestation: 1% physical cruelty, 4.8% emotional cruelty, 5.1% any victimisation; 33 months postpartum: 2.9% physical, 10.8% emotional, 11% any victimisation). Women who reported being victimised during pregnancy also reported significantly higher levels of social adversity during pregnancy. The number of social adversities reported during pregnancy also predicted postpartum victimisation. Women who reported only one adversity during pregnancy were 2.73 (95% CI, 2.16 -3.45) times more likely to report physical victimisation at 33 months postpartum. Women who reported 5 adversities during pregnancy were 14.69 (95% CI, 7.35-29.37) times more likely to report such victimisation at 33 months postpartum. For emotional cruelty, women who reported only one adversity during pregnancy were 2.10 (95% CI 1.80 -2.46) times more likely to report emotional victimisation at 33 months postpartum and 6.10 (95% CI 3.51-10.59) times more likely to report such victimisation when five or more adversities were present during pregnancy. Conclusions Levels of social adversity reported in pregnancy are important predictors of concurrent and future victimisation. Screening for social adversity factors could help identify women at high risk for future domestic violence.
Tobacco smoking and alcohol consumption are well‐established risk factors for head and neck cancer. The prognostic role of smoking and alcohol intake at diagnosis have been less well studied. We analysed 1,393 people prospectively enrolled into the Head and Neck 5000 study (oral cavity cancer, n=403; oropharyngeal cancer, n=660; laryngeal cancer, n=330) and followed up for a median of 3.5 years. The primary outcome was all‐cause mortality. We used Cox proportional hazard models to derive minimally adjusted (age and gender) and fully adjusted (age, gender, ethnicity, stage, comorbidity, body mass index, HPV status, treatment, education, deprivation index, income, marital status, and either smoking or alcohol use) mortality hazard ratios (HR) for the effects of smoking status and alcohol intake at diagnosis. Models were stratified by cancer site, stage and HPV status. The fully‐adjusted HR for current versus never‐smokers was 1.7 overall (95% confidence interval [CI] 1.1, 2.6). In stratified analyses, associations of smoking with mortality were observed for oropharyngeal and laryngeal cancers (fully adjusted HRs for current smokers: 1.8 (95% CI=0.9, 3.40 and 2.3 (95% CI=0.8, 6.4)). We found no evidence that people who drank hazardous to harmful amounts of alcohol at diagnosis had a higher mortality risk compared to non‐drinkers (HR=1.2 (95% CI=0.9, 1.6)). There was no strong evidence that HPV status or tumour stage modified the association of smoking with survival. Smoking status at the time of a head and neck cancer diagnosis influenced all‐cause mortality in models adjusted for important prognostic factors.
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