Wansu Chen

Sociodemographic characteristics of members of a large, integrated health care system: comparison with US Census Bureau data.

BACKGROUND Data from the memberships of large, integrated health care systems can be valuable for clinical, epidemiologic, and health services research, but a potential selection bias may threaten the inference to the population of interest. METHODS We reviewed administrative records of members of Kaiser Permanente Southern California (KPSC) in 2000 and 2010, and we compared their sociodemographic characteristics with those of the underlying population in the coverage area on the basis of US Census Bureau data. RESULTS We identified 3,328,579 KPSC members in 2000 and 3,357,959 KPSC members in 2010, representing approximately 16% of the population in the coverage area. The distribution of sex and age of KPSC members appeared to be similar to the census reference population in 2000 and 2010 except with a slightly higher proportion of 40 to 64 year olds. The proportion of Hispanics/Latinos was comparable between KPSC and the census reference population (37.5% vs 38.2%, respectively, in 2000 and 45.2% vs 43.3% in 2010). However, KPSC members included more blacks (14.9% vs 7.0% in 2000 and 10.8% vs 6.5% in 2010). Neighborhood educational levels and neighborhood household incomes were generally similar between KPSC members and the census reference population, but with a marginal underrepresentation of individuals with extremely low income and high education. CONCLUSIONS The membership of KPSC reflects the socioeconomic diversity of the Southern California census population, suggesting that findings from this setting may provide valid inference for clinical, epidemiologic, and health services research.

The association of obesity and asthma severity and control in children

BACKGROUND The association between obesity and asthma severity and control in children is not well understood. OBJECTIVE The objective of this study was to examine the association of childhood body mass index (BMI) percentile for age of 85% or greater with the number of β-agonist canisters dispensed, corticosteroid courses, emergency department visits, and hospitalizations for asthma. METHODS A retrospective cohort of 32,321 children aged 5 to 17 years and given a diagnosis of asthma who received at least 1 asthma (controller or rescue) medication and were enrolled in Kaiser Permanente from 2004-2008 was identified. Outcomes from electronic medical records included β-agonist canister and nebulizer units dispensed per year, hospitalizations and emergency department visits for asthma exacerbations, and oral corticosteroid courses. Potential confounding factors known to influence asthma outcomes were also collected: demographics, parental education level, asthma controller use, gastroesophageal reflux disease diagnosis, and diabetes mellitus diagnosis. Multiple logistic regression models were used to measure the independent association of BMI status with outcomes. RESULTS Even after adjusting for demographics, parental education level, asthma controller use, and gastroesophageal reflux disease and diabetes mellitus diagnoses, overweight (BMI percentile for age, 85% to 94%) and obese (BMI percentile for age, ≥ 95%) children were more likely to have increased β-agonists dispensed (odds ratio of 1.15 [95% CI, 1.02-1.27] and odds ratio of 1.17 [95% CI, 1.06-1.29], respectively) and increased risk for oral corticosteroids dispensed (odds ratio of 1.21 [95% CI, 1.13-1.29] and odds ratio of 1.28 [95% CI, 1.21-1.36], respectively) compared with normal-weight (BMI percentile for age, 16% to 84%) children. CONCLUSIONS Our findings suggest that childhood obesity is associated with an increased risk of worse asthma control and exacerbations.

Phenotypes determined by cluster analysis in severe or difficult-to-treat asthma

BACKGROUND Asthma phenotyping can facilitate understanding of disease pathogenesis and potential targeted therapies. OBJECTIVE To further characterize the distinguishing features of phenotypic groups in difficult-to-treat asthma. METHODS Children ages 6-11 years (n = 518) and adolescents and adults ages ≥12 years (n = 3612) with severe or difficult-to-treat asthma from The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR) study were evaluated in this post hoc cluster analysis. Analyzed variables included sex, race, atopy, age of asthma onset, smoking (adolescents and adults), passive smoke exposure (children), obesity, and aspirin sensitivity. Cluster analysis used the hierarchical clustering algorithm with the Ward minimum variance method. The results were compared among clusters by χ(2) analysis; variables with significant (P < .05) differences among clusters were considered as distinguishing feature candidates. Associations among clusters and asthma-related health outcomes were assessed in multivariable analyses by adjusting for socioeconomic status, environmental exposures, and intensity of therapy. RESULTS Five clusters were identified in each age stratum. Sex, atopic status, and nonwhite race were distinguishing variables in both strata; passive smoke exposure was distinguishing in children and aspirin sensitivity in adolescents and adults. Clusters were not related to outcomes in children, but 2 adult and adolescent clusters distinguished by nonwhite race and aspirin sensitivity manifested poorer quality of life (P < .0001), and the aspirin-sensitive cluster experienced more frequent asthma exacerbations (P < .0001). CONCLUSION Distinct phenotypes appear to exist in patients with severe or difficult-to-treat asthma, which is related to outcomes in adolescents and adults but not in children. The study of the therapeutic implications of these phenotypes is warranted.

Prevalence and Timing of Postpartum Glucose Testing and Sustained Glucose Dysregulation After Gestational Diabetes Mellitus

OBJECTIVE To estimate the prevalence of postpartum glucose testing within 6 months of pregnancies complicated by gestational diabetes mellitus (GDM), assess factors associated with testing and timing of testing after delivery, and report the test results among tested women. RESEARCH DESIGN AND METHODS This was a retrospective study of 11,825 women who were identified as having GDM using the 100-g oral glucose tolerance test (OGTT) from 1999 to 2006. Postpartum testing (75-g 2-h OGTT or fasting plasma glucose [FPG]) within 6 months of delivery and test results from laboratory databases are reported. Postpartum test results are categorized as normal, impaired fasting glucose (IFG) and/or impaired glucose tolerance (IGT), and provisionally diabetic. RESULTS About half (n = 5,939) the women were tested with either a FPG or 75-g OGTT from 7 days to 6 months postpartum. Of these women, 46% were tested during the 6- to 12-week postpartum period. Odds of testing were independently associated with age, race/ethnicity, household income, education, foreign-born status, parity, mode of delivery, having a postpartum visit, having GDM coded at discharge, and pharmacotherapy for GDM. Of the 5,857 women with test results, 16.3% (n = 956) had IFG/IGT and 1.1% (n = 66) had provisional diabetes. After adjustment for demographic and clinical factors, abnormal postpartum test results was associated with having required insulin, glyburide, or metformin during pregnancy and with longer period from delivery to postpartum testing. CONCLUSIONS After a pregnancy complicated by GDM, automated orders for postpartum testing with notification to physicians and electronically generated telephone and e-mail reminder messages to patients may improve the rates of postpartum testing for persistence of glucose intolerance.

High Blood Eosinophil Count Is a Risk Factor for Future Asthma Exacerbations in Adult Persistent Asthma

BACKGROUND Exacerbation-associated uncontrolled asthma represents a major public health problem. The relationship of elevated blood eosinophils to this process needs study. OBJECTIVE To determine whether a high blood eosinophil count is a risk factor for future asthma exacerbations in adult persistent asthma. METHODS By using electronic pharmacy and health care data from Kaiser Permanente Southern California, 2392 patients, ages 18 to 64 years, were identified who met the Health Effectiveness Data and Information Set 2-year criteria for persistent asthma, did not manifest chronic obstructive pulmonary disease and other major illnesses, and had a blood eosinophil determination in 2010. Exacerbations (primary outcome) were defined as asthma outpatient visits that required systemic corticosteroid dispensing within ±7 days or asthma emergency department visits or hospitalizations. A period of ≥8 days defined a new exacerbation. Multivariate modelling used negative binomial and Poisson regression to examine the association between a blood eosinophil count determined in 2010 and risk of exacerbations, and ≥7 short-acting β2-agonist (SABA) canisters dispensed (secondary outcome) in 2011 by adjusting for demographics, comorbidities, and asthma burden. RESULTS The rate of asthma exacerbations in 2011 was 0.41 events per person year (95% CI, 0.37-0.45). Eosinophil count ≥400/mm(3) in 2010 was a risk factor for asthma exacerbations in 2011 (adjusted rate ratio 1.31 [95% CI, 1.07-1.60]; P = .009) and ≥7 SABA dispensed (adjusted risk ratio 1.17 [95% CI, 1.03-1.1.33]; P = .015). CONCLUSION A high blood eosinophil count is a risk factor for increased future asthma exacerbations and excessive short-acting β2-agonist use after adjustment of potential confounders in adults with persistent asthma, which suggests a higher disease burden in patients with asthma and with high blood eosinophil counts.

Estimating fetal weight in the management of macrosomia.

The purpose of this review is to examine the evidence that, including estimates of fetal macrosomia in patient care, will decrease adverse perinatal outcomes. A literature search for the years 1980 to 1999 was used. Shoulder dystocia and brachial plexus injuries occur more often in macrosomic than in non-macrosomic neonates. However, 26 to 58 percent of shoulder dystocias and 24 to 44 percent of brachial plexus injuries occur to babies weighing less than 4000 gm. Persistence of impairment is extremely rare. Neither historical nor clinical factors have strong positive predictive values for macrosomia. From 15 to 81 percent of the babies predicted to be macrosomic are confirmed by birth weight. Of babies determined to be macrosomic at birth, only 50 to 100 percent were successfully predicted. Shoulder dystocia and brachial plexus injuries are unpredictable events. Available evidence suggests that planned interventions based on estimates of fetal weight do not reduce the incidence of shoulder dystocia and do not decrease adverse outcomes attributable to fetal macrosomia.

Racial/Ethnic differences in ischemic stroke rates and the efficacy of warfarin among patients with atrial fibrillation.

Background and Purpose— Warfarin reduces stroke risk in studies of predominantly white patients with atrial fibrillation (AF). Whether nonwhites also have lower rates of stroke while treated with warfarin is unclear. Methods— A multiethnic stroke-free cohort hospitalized with nonrheumatic AF was identified in a large health maintenance organization. Stroke risk factors (advanced age, diabetes, hypertension, and heart failure), warfarin use, and anticoagulation intensity were assessed. Crude ischemic stroke rates were calculated by Poisson regression for each group while using and not using warfarin. Cox proportional hazard models were constructed to assess the independent effect of race/ethnicity on ischemic stroke. Results— Between 1995 and 2000, we identified 18 867 AF hospitalizations (78.5% white, 8% black, 9.5% Hispanic, and 3.9% Asian). Over the course of 63 204 person-years follow-up (median, 3.3 years), 1226 ischemic strokes were identified. The percent-time on warfarin did not differ by race/ethnicity. The median percent-time on warfarin that international normalized ratio was 2 to 3 was 54.5% overall, but it was lower in blacks at 47.8%, whereas the other groups had a rate of ≈54%. The rate ratios (95% CI) of ischemic stroke with warfarin compared to without warfarin for whites, blacks, Hispanics, and Asians were 0.79 (0.68 to 0.90), 0.92 (0.65 to 1.30), 0.71 (0.48 to 1.05), and 0.65 (0.34 to 1.23), respectively. Conclusions— In this cohort, we did not observe a statistically significant lower rate of stroke with warfarin therapy among nonwhites (in particular blacks) with previous AF hospitalizations. The relatively small numbers of nonwhites renders our estimates less than precise and should be interpreted with caution.

Racial/Ethnic Differences in the Prevalence of Atrial Fibrillation Among Older Adults—A Cross-Sectional Study

BACKGROUND Atrial fibrillation affects 4% to 8% of individuals over 60 years of age based on studies of predominantly white populations, whether this is true among nonwhite individuals is not clear. This study was undertaken to define racial/ethnic differences in atrial fibrillation prevalence among a large community cohort. METHODS This is a cross-sectional study. In 2008, there were 430,317 members aged 60 years or older in a large California health maintenance organization. By searching International Classification of Diseases, Ninth Revision codes and electronic electrocardiographic archives, we identified all members in this age group with primary, nonvalvular atrial fibrillation. Race/ethnicity data were assigned using health plan enrollment, service utilization, Asian/Hispanic surname and geocoding methods, and was available for 80.5% of members (79.8% of non-atrial fibrillation and 92% of atrial fibrillation), 99% of which were white, black, Asian, or Hispanic. We assessed the age- and gender-specific atrial fibrillation prevalence rates for each racial/ethnic group. The effect of race/ethnicity on atrial fibrillation was analyzed with logistic regression methods adjusting for potential confounders. RESULTS The overall atrial fibrillation prevalence was 5.3%. Among members with assigned race/ethnicity data, the prevalence among whites, blacks, Asians, and Hispanics was 8.0%, 3.8%, 3.9%, and 3.6%, respectively. The adjusted odds ratios (95% confidence intervals) of atrial fibrillation among blacks, Asians, and Hispanics with whites as referent were 0.49 (0.47-0.52), 0.68 (0.64-0.72), and 0.58 (0.55-0.61), respectively. CONCLUSIONS Atrial fibrillation is less prevalent in older nonwhite individuals than whites. White race/ethnicity is associated with significantly greater odds for atrial fibrillation compared to blacks, Asians, and Hispanics, after adjusting for comorbidities associated with the development of atrial fibrillation.

Overweight/Obesity and Risk of Seasonal Asthma Exacerbations

BACKGROUND Obesity is associated with an increased risk for asthma exacerbations, but whether this risk is related to the season of exacerbation is not known. OBJECTIVE To determine the relationship of increased body mass index (BMI) to the season of asthma exacerbation. METHODS Study subjects were adult (aged 18-65 years) and children (aged 5-17 years) health plan members with persistent asthma in 2008 for whom a BMI measurement was available. BMI categories were normal (<25 kg/m(2)), overweight (25-29.9 kg/m(2)), and obese (≥30 kg/m(2)). Exacerbations were defined as oral corticosteroid dispensings linked to an asthma encounter in the spring, summer, fall, or winter of 2009. RESULTS The cohort included 17,316 adults and 10,700 children. There was a significant (P < .05) linear increase with BMI category in the proportion of adults with exacerbations in every season and in the proportion of children with exacerbations during fall and winter. Relationships of overweight or obesity (vs normal weight) to fall and winter exacerbations remained significant in both adults and children after adjustment for sex and education. In a generalized estimating equation model, both BMI status and season (spring, fall, and winter) were related to exacerbations. Moreover, we noted a significant interaction in adults (P = .03) but not children (P = .97) of the BMI-exacerbation association by season (fall-winter vs spring-summer). CONCLUSION Higher BMI values increased the risk for asthma exacerbations in adults and children with persistent asthma, particularly for fall-winter exacerbations in adults. Potential mechanisms for these findings, including vitamin D status, viral infections, and corticosteroid responsiveness, merit further study.

Body weight and height data in electronic medical records of children.

OBJECTIVE Data entry errors may occur in body weights and heights assessed during routine medical care. These errors may affect data quality markedly and create a large number of biologically implausible values. To address this issue, we evaluated the quality of body weight and height measures for children based on sequential health care encounters. METHODS We evaluated the weight and height data of children aged 0-18 years receiving care at Kaiser Permanente Southern California medical centers. Error rates were calculated before and after excluding implausible values for height and weight as recorded in the electronic medical chart reviews. RESULTS The error rates in weight and height data of children aged <2, 2-5, 6-9, 10-13, 14-18 years were 0.4%, 0.7%, 1.0%, 1.0% and 0.7%, respectively. The most frequently identified errors were implausibly low values for height and implausibly high values for weight. After excluding implausible values, the error rates were 0.4%, 0.4%, 0.6%, 0.4% and 0.1%, respectively. The sensitivity of our approach to detect errors was 10.9%, 36.6%, 32.9%, 59.2%, and 82.5%, respectively. CONCLUSIONS Error rates in weight and height recorded in the electronic medical record during routine medical care are low, raising the potential for this information to be used for population care management. With little effort and with the recording of this information at each encounter, error rates can be further lowered to avoid misclassification of children as obese.