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.

Context Approximately 1 million episodes of herpes zoster occur annually in the United States. Although prelicensure data provided evidence that herpes zoster vaccine works in a select study population under idealized circumstances, the vaccine needs to be evaluated in field conditions. Objective To evaluate risk of herpes zoster after receipt of herpes zoster vaccine among individuals in general practice settings.

Objective To estimate the prevalence of extreme obesity in a large, multiethnic contemporary cohort of children and adolescents. Study design In a cross-sectional study, measured weight and height were extracted from electronic medical records of 710 949 patients aged 2 to 19 years (87.8% of eligible patients) who were enrolled in an integrated prepaid health plan in 2007 and 2008. Prevalence of extreme obesity was defined as body mass index (BMI)-for-age ≥1.2 times 95th percentile or BMI ≥35 kg/m2. Results Extreme obesity was observed in 7.3% of boys and 5.5% of girls. The prevalence peaked at 10 years of age in boys and at 12 years of age with a bimodal distribution in girls (second peak at 18 years; P value for sex × age interaction = .036). The prevalence of extreme obesity varied in ethnic/racial and age groups, with the highest prevalence in Hispanic boys (as high as 11.2%) and African-American girls (as high as 11.9%). Conclusion Extreme obesity in Southern California youth is frequently observed at relatively young ages. The shift toward extreme body weights is likely to cause an enormous burden of adverse health outcomes once these children and adolescents grow older.

Background A number of studies have found an increased risk of lower extremity injuries in obese patients. Most studies, however, are unable to provide stable population-based estimates based on the degree of obesity and few assess the risk pertaining to more detailed fracture location in the lower extremities. Questions/purposes We therefore investigated the relationship between obesity and lower extremity fractures in different age and fracture locations in a stable population. Methods This is a population-based, cross-sectional study from the electronic medical records of 913,178 patients aged 2 to 19 years. The body mass index (BMI) for each patient in the cohort was used to stratify patients into five weight classes (underweight, normal weight, overweight, moderate obesity, and extreme obesity) based on BMI for age. Records were assessed for the occurrence of lower extremity fractures for each cohort member. The associations among the five weight classes and specific lower extremity fractures were estimated using multiple logistic regression models and expressed with odds ratios (ORs) and 95% confidence intervals (CIs) using multivariate analysis to adjust for patient demographic variables.

Objective To investigate the prevalence of polycystic ovary syndrome (PCOS) in adolescents and its association with obesity. Design Cross-sectional study using electronic medical records. Setting Integrated health care delivery system in Southern California. Patients Adolescents aged 15–19 years (n= 137,502). Interventions None. Main Outcome Measures PCOS diagnosed or defined according to NIH criteria. Results The prevalence of a confirmed diagnosis of PCOS was 0.56%, and increased to 1.14% when undiagnosed cases with documented symptoms qualifying for PCOS according to NIH criteria were included. Compared to normal/underweight girls, the ORs (95% CI) for confirmed PCOS diagnosis were 3.85 (3.04–4.88), 10.25 (8.16–12.84) and 23.10 (18.66–28.61) for overweight, moderately obese, and extremely obese adolescents, respectively (P-trend<0.001) after adjusting for potential confounders. When adolescents with two or more supportive diagnoses were included (diagnosed and undiagnosed PCOS-NIH) the ORs (95% CI) for PCOS-NIH by weight class were significantly attenuated to 2.95 (2.53–3.44), 6.73 (5.78–7.83), and 14.65 (12.73–16.86) for overweight, moderately obese, and extremely obese adolescents, respectively. Conclusions Overweight and obesity were associated with higher odds of PCOS in adolescents. Studies based solely on diagnosis codes may underestimate the prevalence of PCOS and overestimate the magnitude of the association between obesity and PCOS.