Beyond logistic regression: structural equations modelling for binary variables and its application to investigating unobserved confounders

Abstract Background Structural equation modelling (SEM) has been increasingly used in medical statistics for solving a system of related regression equations. However, a great obstacle for its wider use has been its difficulty in handling categorical variables within the framework of generalised linear models. Methods A large data set with a known structure among two related outcomes and three independent variables was generated to investigate the use of Yule's transformation of odds ratio (OR) into Q-metric by (OR-1)/(OR+1) to approximate Pearson's correlation coefficients between binary variables whose covariance structure can be further analysed by SEM. Percent of correctly classified events and non-events was compared with the classification obtained by logistic regression. The performance of SEM based on Q-metric was also checked on a small (N = 100) random sample of the data generated and on a real data set. Results SEM successfully recovered the generated model structure. SEM of real data suggested a significant influence of a latent confounding variable which would have not been detectable by standard logistic regression. SEM classification performance was broadly similar to that of the logistic regression. Conclusion The analysis of binary data can be greatly enhanced by Yule's transformation of odds ratios into estimated correlation matrix that can be further analysed by SEM. The interpretation of results is aided by expressing them as odds ratios which are the most frequently used measure of effect in medical statistics.</p

Baixa cobertura da vacina contra COVID-19 e altas taxas de mortalidade por COVID-19 em idosos no Brazil

Introduction: In 2021, Brazil started a nationwide vaccination against COVID-19 but the emergence of the P.1 variant of SARS-CoV-2, more transmissible and resistant to immunity from the previous infection, rapidly led to a record increase in COVID-19 mortality. Methods: Secondary data on COVID-19 deaths and vaccination coverage were retrieved to examine COVID-19 mortality rate (MR) evolution as anti-COVID-19 vaccination advanced in Brazil in 2021. Poisson regression with adjustment for age and federal states was used to calculate the MR. Results; By mid-April 2021, MR increased 2-3 times compared to the already high level in January for the people of 60 years or older, reaching the highest epidemic level of 5-15 per 100.000 in this age group. Despite a declining time trend followed, by the end of May, the MR level was still about 50% and 80% higher for the 40-79 and 80 years or older. The first dose of anti-COVID-19 coverage reached 80% for the 60-69 years old and exceeded 95% for those of 70 years or older, but the second dose was applied to only 26%, 76%, and 64% of the 60-69, 70-79, and 80 years or older, respectively. The average age-standardized MR over the study time was the highest in northern Brazilian states of Rondônia, Amazonas, Acre, and Roraima (range 6-8.4 per 100.000). Conclusion: Anti-COVID-19 vaccination coverage was below the level necessary to protect Brazilians from rising MR between January and May 2021. Urgent measures are needed to increase the vaccine supply and the adherence to non-pharmacological protective measures.Introdução: Brasil começou vacinar contra COVID-19 em 2021, mas o surgimento da variante P.1 do SARS-Cov-2, mais transmissível e resistente, rapidamente levou a aumento recorde em mortalidade por COVID-19. Métodos – Foram levantados dados secundários sobre mortes e cobertura vacinal relacionadas a COVID-19, para examinar a evolução da taxa de mortalidade (TM) com avanço da vacinação. Utilizou-se a regressão de Poisson com ajuste para idade e as unidades federadas. Resultados – Em abril, a TM aumentou 2-3 vezes comparado com começo do ano 2021 em pessoas com 60 ou mais anos de idade (60+), atingindo o nível recorde de 5-15 por 100.000. Apesar do subsequente declínio, no final de maio a taxa ainda estava aproximadamente 50% e 80% mais alta que no começo do ano para faixas etárias de 40-79 e 80+ anos, respectivamente. As pessoas com 70+ anos ultrapassaram a cobertura vacinal de 95%, enquanto aqueles de 60-69 anos chegaram à 80% da cobertura com a primeira dose da vacina. Porém, a segunda dose foi aplicada a somente 26%, 76%, e 64% das pessoas com 60-69, 70-79, e 80+ anos, respectivamente. As mais altas taxas de 6 a 8.4 per 100.000, ajustadas por faixa etária, foram registradas em Rondônia, Amazonas, Acre, e Roraima. Conclusão – Cobertura vacinal contra COVID-19 não atingiu os níveis necessários para proteger os Brasileiros contra crescente mortalidade por esta doença entre janeiro e maio de 2021. É preciso tomar medidas urgentes para aumentar o suprimento das vacinas e aderência às medidas preventivas não farmacológicas

Epidemiological trends and risk factors for tobacco, alcohol and drug use among adolescents in Scotland, 2002–13

Background This study estimates trends in prevalence, and patterns, of individual and multiple substance use between 2002 and 2013 amongst adolescents in Scotland. Methods The study uses data from 134 387 participants of the biennial national ‘Scottish Schools Adolescent Lifestyle and Substance Use Survey’ on smoking, alcohol and illicit drug use. Current regular use and current heavy use of smoking, alcohol, illicit drugs and multiple substances was measured. Time trends in the prevalence of each outcome were estimated using univariate and multivariate logistic regression. Results Regular smoking, alcohol, illicit drug and multiple substance use declined significantly amongst adolescents in Scotland. However, multivariate analyses that focussed upon high-risk levels of these behaviours revealed an upward linear trend in heavy alcohol (OR = 1.06; 95% CI: 1.04, 1.07) and heavy illicit drug (OR = 1.04; 95% CI: 1.00, 1.08) use (P < 0.05). Non-white pupils were more likely to be involved in individual and multiple substance use than ethnically white British pupils. In comparison to pupils from the least deprived socioeconomic quintile, pupils from the most deprived quintile had increased odds of 1.41 (95% CI: 1.02, 1.97; P < 0.05) and 1.62 (95% CI: 1.14, 2.29; P < 0.05) of being regular and heavy multiple substance users, respectively. Conclusions Further effort is required to tackle heavy alcohol and heavy illicit drug use amongst adolescents in Scotland. Prevention strategies should be informed by the risk profiles of substance misusers and evidence around the clinical and cost-effectiveness of preventive interventions

Self-reported health and socio-economic inequalities in England, 1996–2009 : repeated national cross-sectional study

Tackling social inequalities in health has been a priority for recent UK governments. We used repeated national cross-sectional data for 155,311 participants (aged ≥16 years) in the Health Survey of England to examine trends in socio-economic inequalities in self-reported health over a recent period of sustained policy focus by successive UK governments aimed at tackling social inequalities in health. Socio-economic related inequalities in self-reported health were estimated using the Registrar General's occupational classification (1996–2009), and for sensitivity analyses, the National Statistics Socio-Economic Classification (NS-SEC; 2001–2011). Multi-level regression was used to evaluate time trends in General Health Questionnaire (GHQ-12) scores and bad or very bad self-assessed health (SAH), as well as EQ-5D utility scores. The study found that the probability of reporting GHQ-12 scores ≥4 and ≥ 1 was higher in those from lower social classes, and decreased for all social classes between 1997 and 2009. For SAH, the probability of reporting bad or very bad health remained relatively constant for social class I (professional) [0.028 (95%CI: 0.026, 0.029) in 1996 compared to 0.028 (95%CI: 0.024, 0.032) in 2009], but increased in lower social classes, with the greatest increase observed amongst those in social class V (unskilled manual) [0.089 (95%CI: 0.085, 0.093) in 1996 compared to 0.155 (95%CI: 0.141, 0.168) in 2009]. EQ-5D utility scores were lower for those in lower social classes, but remained comparable across survey years. In sensitivity analyses using the NS-SEC, health outcomes improved from 2001 to 2011, with no evidence of widening socio-economic inequalities. Our findings suggest that socio-economic inequalities have persisted, with evidence of widening for some adverse self-reported health outcomes

Effectiveness of DNA-recombinant anti-hepatitis B vaccines in blood donors: a cohort study

<p>Abstract</p> <p>Background</p> <p>Although various studies have demonstrated efficacy of DNA-recombinant anti-hepatitis B vaccines, their effectiveness in health care settings has not been researched adequately. This gap is particularly visible for blood donors, a group of significant importance in the reduction of transfusion-transmitted hepatitis B.</p> <p>Methods</p> <p>This is a double cohort study of 1411 repeat blood donors during the period 1998–2002, involving a vaccinated and an unvaccinated cohort, with matching of the two in terms of sex, age and residence. Average follow-up was 3.17 person-years. The outcome measure was infection with hepatitis B virus (HBV), defined by testing positive on serologic markers HBsAg or anti-HBC. All blood donors were from the blood bank in Joaçaba, federal state of Santa Catarina, Brazil.</p> <p>Results</p> <p>The cohorts did not differ significantly regarding sex, age and marital status but the vaccinated cohort had higher mean number of blood donations and higher proportion of those residing in the county capital Joaçaba. Hepatitis B incidences per 1000 person-years were zero among vaccinated and 2,33 among non-vaccinated, resulting in 100% vaccine effectiveness with 95% confidence interval from 30,1% to 100%. The number of vaccinated persons necessary to avoid one HBV infection in blood donors was estimated at 429 with 95% confidence interval from 217 to 21422.</p> <p>Conclusion</p> <p>The results showed very high effectiveness of DNA-recombinant anti-HBV vaccines in blood donors. Its considerable variation in this study is likely due to the limited follow-up and the influence of confounding factors normally balanced out in efficacy clinical trials.</p