A Comparison of Statistical Methods to Construct Confidence Intervals and Fiducial Intervals for Measures of Health Disparities.

Health disparities are differences in health status across different socioeconomic groups. Classical methods, e.g., the Delta method, have been used to estimate the standard errors of estimated measures of health disparities and to construct confidence intervals for these measures. However, the confidence intervals constructed using the classical methods do not have good coverage properties for situations involving sparse data. In this article, we introduce three new methods to construct fiducial intervals for measures of health disparities based on approximate fiducial quantities. Through a comprehensive simulation study, We compare the empirical coverage properties of the proposed fiducial intervals against two Monte Carlo simulation-based methods-utilizing either a truncated Normal distribution or the Gamma distribution-as well as the classical method. The findings of the simulation study advocate for the adoption of the Monte Carlo simulation-based method with the Gamma distribution when a unified approach is sought for all health disparity measures.

A Novel Methodological Approach to Measure Linear Trends in Health Inequalities: Proof of Concept With Adolescent Smoking in Europe.

We describe a new method for presenting and interpreting linear trends in health inequalities, and present a proof-of-concept analysis of inequalities in smoking among adolescents in Europe. We estimated the regression line of the assumed linear relationship between smoking prevalence in low- and high-socioeconomic status (SES) youth over time. Using simulation, we constructed a 95% confidence interval (CI) for the smoking prevalence in low-SES youth for when this would be 0% in high-SES youth, and we calculated the likelihood of eradicating smoking inequality (<5% for both low and high SES). This method was applied to data on adolescents aged 15-16 years (n = 250,326) from 23 European countries, derived from the 2003-2015 European Survey Project on Alcohol and Other Drugs. Smoking prevalence decreased more slowly among low- than among high-SES adolescents. The estimated smoking prevalence was 9.4% (95% CI: 6.1, 12.7) for boys and 5.4% (95% CI: 1.4, 9.2) for girls with low SES when 0% with high SES. The likelihood of eradicating smoking inequality was <1% for boys and 37% for girls. We conclude that this novel methodological approach to trends in health inequalities is feasible in practice. Applying it to trends in smoking inequalities among adolescents in Europe, we found that Europe is currently not on track to eradicate youth smoking across SES groups.

Reflection on modern methods: understanding bias and data analytical strategies through DAG-based data simulations.

Directed acyclic graphs (DAGs) are increasingly used in epidemiology to identify and address different types of bias. The present work aims to demonstrate how DAG-based data simulation can be used to understand bias and compare data analytical strategies in an educational context. Examples based on classical confounding situations and an M-DAG are examined and used to introduce basic concepts and demonstrate some important features of regression analysis, as well as the harmful effect of adjusting for a collider variable. Other potential uses of DAG-based data simulation include systematic comparisons of data analytical strategies or the evaluation of the role of uncertainties in a hypothesized DAG structure, including other types of bias such as information bias. DAG-based data simulations, like those presented here, should facilitate the exploration of several key epidemiological concepts, DAG theory and data analysis. Some suggestions are also made on how to further expand the ideas from this study.

Application of the Abridged SimSmoke model to four Eastern Mediterranean countries.

INTRODUCTION: The WHO established the MPOWER policy package to boost the implementation of the WHO Framework Convention for Tobacco Control (WHO FCTC) in 2008 and to provide practical guidance on policies effective at reducing smoking rates. An easily applied Abridged SimSmoke was developed to help countries gauge the effect of these policies using data from the WHO MPOWER/WHO Report (MPOWER Report) and is applied to four Eastern Mediterranean countries. METHODS: The number of smokers in a country is calculated using the country's smoking prevalence and population. Policy effect sizes, based on previously validated SimSmoke models, are applied to the smoker populations to determine the reduction in the number of smokers resulting from implementing policies. The number of smoking-attributable deaths is derived based on findings that half of those smokers alive today will die from smoking. RESULTS: Within 40 years, implementing the complete set of MPOWER policies is projected to reduce smoking prevalence by 29% (range 15%, 41%) and avert almost 1 (range 0.5, 1.4) million deaths in Egypt, reduce smoking prevalence by 52% (range 36%, 66%) and avert 156 000 (106 000, 196 000) deaths in Lebanon, reduce smoking prevalence by 56% (range 40%, 69%) and avert 3.5 (range 2.5, 4.3) million deaths in Pakistan, and reduce smoking prevalence by 37% (range 21%, 51%) and avert 245 000 (range 138 000, 334 000) deaths in Tunisia. CONCLUSIONS: The Abridged SimSmoke model has been used to show the number of deaths from smoking and how MPOWER policies can be used to reach the WHO non-communicable deaths voluntary target for cigarette use reduction in four countries.

Potential risk factors associated with subtypes of uterine leiomyomata.

OBJECTIVE: To compare potential risk factors for uterine leiomyomata (UL) subtypes among premenopausal African American and Caucasian women. METHODS: This cross-sectional study included 986 premenopausal women, aged 35 to 49 years old, from the National Institute of Environmental Health Sciences (NIEHS) Uterine Fibroid Study (UFS). Uterine leiomyomata were subtyped as submucosal, intramural/subserosal, and diffuse, based on ultrasound examinations. RESULTS: For both ethnic groups, age, age at menarche, body mass index, and current physical activity had similar associations across the 3 UL subtypes. Inverse associations with pregnancies after age 24 appeared to be stronger for the submucosal subtype. Current smoking was associated only with diffuse UL (adjusted odds ratio [aOR] = 1.97, 95% CI: 1.11, 3.51 in African Americans, aOR = 3.00, 95% CI: 1.07, 8.38 in Caucasians). CONCLUSIONS: Although the 2 focal UL subtypes had similar risk factor profiles, the diffuse UL subtype appeared to have a distinctive risk profile with regard to current smoking. Further study of the diffuse heterogeneity seen with uterine ultrasound is needed.

Uterine leiomyomata associated with self-reported stress urinary incontinence.

AIMS: To investigate the association between the presence and characteristics of uterine leiomyomata (UL) and self-reported stress urinary incontinence (SUI). METHODS: The study included 836 premenopausal participants (474 African American and 362 Caucasian) in the National Institute of Environmental Health Sciences (NIEHS) Uterine Fibroid Study. UL were characterized at baseline with ultrasound screening, and SUI was assessed at follow-up (after 4 years, on average). Linear risk models were used to estimate adjusted prevalence differences (aPD) and 95% confidence intervals (CI), controlling for age, ethnicity, body mass index (BMI), and number of deliveries. RESULTS: Compared with women without UL, SUI prevalence was higher among women with any UL (aPD = 7.4%, 95% CI 0.4-14.3) and women with UL 2-4 cm (aPD = 9.6%, 95% CI 1.3-17.9). Marginally significant results were found for the presence of UL > or =4 cm and anterior UL > or =2 cm. CONCLUSIONS: The observed 7% increase in prevalence of this common condition for women with UL is of clinical importance. Further research is needed before concluding that treatment for larger UL might enhance SUI treatment in some women.

Prevalence of hip symptoms and radiographic and symptomatic hip osteoarthritis in African Americans and Caucasians: the Johnston County Osteoarthritis Project.

OBJECTIVE: To report contemporary estimates of the prevalence of hip-related osteoarthritis (OA) outcomes in African Americans and Caucasians aged>or=45 years. METHODS: Weighted prevalence estimates and their corresponding 95% confidence intervals for hip symptoms, radiographic hip OA, symptomatic hip OA, and severe radiographic hip OA were calculated using SUDAAN for age, race, and sex subgroups among 3068 participants (33% African Americans, 38% men) in the baseline examination (1991-97) of The Johnston County Osteoarthritis Project, a population-based study of OA in North Carolina. Radiographic hip OA was defined as Kellgren-Lawrence radiographic grade>or=2, moderate/severe radiographic hip OA as grades 3 and 4, and symptomatic hip OA as hip symptoms in a hip with radiographic OA. RESULTS: Hip symptoms were present in 36%; 28% had radiographic hip OA; nearly 10% had symptomatic hip OA; and 2.5% had moderate/severe radiographic hip OA. Prevalence of all 4 outcomes was higher in older individuals; most outcomes were higher for women and African Americans. CONCLUSION: African Americans in this population do not have a lower prevalence of hip-related OA outcomes as previous studies suggested. Increasing public and health system awareness of the relatively high prevalence of these outcomes, which can be disabling, may help to decrease their effects and ultimately prevent them.

Prevalence of knee symptoms and radiographic and symptomatic knee osteoarthritis in African Americans and Caucasians: the Johnston County Osteoarthritis Project.

OBJECTIVE: To report contemporary estimates of the prevalence of knee-related osteoarthritis (OA) outcomes in African Americans and Caucasians aged > or = 45 years. METHODS: Weighted prevalence estimates for knee symptoms, radiographic knee OA, symptomatic knee OA, and severe radiographic knee OA were calculated for age, ethnic, and sex subgroups, in 3018 participants (33% African Americans, 38% men) in the baseline examination (1991-97) of The Johnston County Osteoarthritis Project, a population-based study of OA in North Carolina. Radiographic knee OA was defined as Kellgren-Lawrence radiographic grade > or = 2, severe radiographic knee OA as grades 3 and 4, and symptomatic knee OA as knee symptoms in a knee with radiographic OA. RESULTS: Knee symptoms were present in 43%, 28% had radiographic knee OA, 16% had symptomatic knee OA, and 8% had severe radiographic knee OA. Prevalence was higher in older individuals and women. African Americans had slightly higher prevalence of knee symptoms, radiographic knee OA, and symptomatic knee OA, but significantly higher prevalence of severe radiographic knee OA compared to Caucasians. CONCLUSION: Policy should be directed to increasing education of the public and the medical community about the high prevalence of these conditions, especially in these subgroups, to decrease their impact and ultimately prevent them.

Serum hyaluronan levels and radiographic knee and hip osteoarthritis in African Americans and Caucasians in the Johnston County Osteoarthritis Project.

OBJECTIVE: Serum hyaluronan (HA) has been proposed as a potential biomarker of osteoarthritis (OA). We examined associations between serum HA and radiographic OA in an ethnically diverse, population-based sample. METHODS: Participants were selected from the Johnston County Osteoarthritis Project, using stratified simple random sampling to achieve balance according to radiographic knee OA status, ethnic group, sex, and age group. Serum HA was measured by enzyme-linked immunosorbent assay. Radiographic OA variables included knee OA, knee OA laterality, knee OA severity, concomitant knee and hip OA, and total number of OA-affected knee and hip joints. Analysis of covariance was used to assess differences in mean serum levels of natural log-transformed HA (ln serum HA) between groups, adjusting for ethnicity, sex, age, body mass index (BMI), and self-reported comorbidities. RESULTS: Levels of ln serum HA were positively associated with all definitions of radiographic OA (P < 0.0001). Levels of ln serum HA were higher in Caucasians (P = 0.0094) and in men (P = 0.0038) and were moderately correlated with age (r = 0.35, P < 0.0001). The associations with radiographic OA, ethnicity, sex, and age remained statistically significant after adjustment (P < 0.0045). There were no interactions between ethnicity and the other covariates. CONCLUSION: These cross-sectional data support a role for serum HA as a biomarker of radiographic OA. The variations in levels of serum HA attributable to ethnicity, sex, and age were not explained by radiographic OA, BMI, or comorbidities. The lack of strong confounding between serum HA and comorbidities further supports a role for serum HA as a potential biomarker.

Ethnic and sex differences in serum levels of cartilage oligomeric matrix protein: the Johnston County Osteoarthritis Project.

OBJECTIVE: Previous descriptions of potential biomarkers of osteoarthritis (OA) have been limited to Caucasians. In the present study, we examined associations between serum levels of cartilage oligomeric matrix protein (COMP) and ethnicity (African American or Caucasian) and sex in the Johnston County Osteoarthritis Project, a population-based study of OA in rural North Carolina. METHODS: All African Americans and a randomly selected sample of Caucasians who had available sera and either no radiographic evidence of knee or hip OA according to the Kellgren/Lawrence (K/L) system (K/L grade 0) or radiographic evidence of knee OA (K/L grade 2 or higher) were included. Serum COMP levels were quantified by sandwich enzyme-linked immunosorbent assay, using monoclonal antibodies 16-F12 and 17-C10. Linear regression models were used to assess relationships between serum levels of natural log-transformed COMP (ln COMP) and ethnicity and sex, controlling for age, height, body mass index (BMI), radiographic OA, and the presence of other symptomatic joints. Radiographic OA was defined in separate models as the presence, severity, and laterality of radiographic knee OA, the co-occurrence of radiographic knee and hip OA, and the number of knees and hips with radiographic OA. RESULTS: The 769 subjects in the study sample had a mean +/- SD age of 62 +/- 10.3 years. Levels of ln COMP were associated with age, BMI, and all definitions of radiographic OA (P = 0.0001), and varied by ethnicity and sex. In adjusted models, ln COMP was higher in African American women than in Caucasian women (P = 0.003) and higher in Caucasian men than Caucasian women (P = 0.0001). There were no statistically significant differences in serum ln COMP levels between African American men and women. CONCLUSION: Serum COMP levels vary by ethnicity and sex. These factors should be considered in the derivation of standards using this, and possibly other, potential biomarkers of OA.