Birth Anomalies in Monozygotic and Dizygotic Twins: Results From the California Twin Registry.

Background: Inherited factors and maternal behaviors are thought to play an important role in the etiology of several congenital malformations. Twin studies can offer additional evidence regarding the contribution of genetic and lifestyle factors to common birth anomalies, but few large-scale studies have been reported.

Methods: We included data from twins (20,803 pairs) from the population-based California Twin Program.

Prevalence and predictors of recent skin examination in a population-based twin cohort.

Background: The incidence of melanoma is increasing worldwide. Guidelines for clinical skin exam for improving early diagnosis of melanoma remain inconsistent, and current data on factors associated with regular skin screening on a population basis are limited.

Methods: We used self-reported data from 50,044 members of the California Twin Program, a population-based cohort of twins born in California between 1908 and 1982, to identify prevalence and determinants of recent clinical screening for skin cancer.

Childhood infections and adult height in monozygotic twin pairs.

Adult height is determined by genetics and childhood nutrition, but childhood infections may also play a role. Monozygotic twins are genetically matched and offer an advantage when identifying environmental determinants. In 2005-2007, we examined the association of childhood infections with adult height in 140 height-discordant monozygotic twin pairs from the California Twin Program.

The USC Adult Twin Cohorts: International Twin Study and California Twin Program.

The study of twin subjects permits the documentation of crude heritability and may promote the identification of specific causal alleles. We believe that at the current time, the chief research advantage of twins as subjects, especially monozygotic twins, is that the commonality of their genetic and cultural identity simplifies the interpretation of biological associations. In order to study genetic and environmental determinants of cancer and chronic diseases, we developed two twin registries, maintained at the University of Southern California: The International Twin Study (ITS) and the California Twin Program (CTP).

Prostate cancer and ambient pesticide exposure in agriculturally intensive areas in California.

In a population-based case-control study in California's intensely agricultural Central Valley (2005-2006), the authors investigated relations between environmental pesticide/fungicide exposure and prostate cancer. Cases (n = 173) were obtained from a population-based cancer registry, and controls (n = 162) were obtained from Medicare listings and tax assessor mailings. Past ambient exposures to pesticides/fungicides were derived from residential history and independently recorded pesticide and land-use data, using a novel geographic information systems approach.

Interaction of area-level socioeconomic status and UV radiation on melanoma occurrence in California.

Background: Melanoma incidence has been correlated strongly and positively with both socioeconomic status (SES) and lower latitude and other measures of ambient UV radiation (UVR). However, because high-SES populations may be colocated in areas of high UVR, we assessed their joint influences on melanoma occurrence to better target subpopulations for melanoma education and screening.

Methods: We obtained from the California Cancer Registry information regarding 23,564 incident cases of invasive cutaneous melanoma among non-Hispanic white residents between January 1, 1998, and December 31, 2002.

The expanding melanoma burden in California hispanics: Importance of socioeconomic distribution, histologic subtype, and anatomic location.

Background: The incidence patterns and socioeconomic distribution of cutaneous melanoma among Hispanics are poorly understood.

Methods: The authors obtained population-based incidence data for all Hispanic and non-Hispanic white (NHW) patients who were diagnosed with invasive cutaneous melanoma from 1988 to 2007 in California. By using a neighborhood-level measure of socioeconomic status (SES), the variables investigated included incidence, thickness at diagnosis, histologic subtype, anatomic site, and the relative risk (RR) for thicker (>2 mm) versus thinner (≤ 2 mm) tumors at diagnosis for groups categorized by SES.

Use of an electrostatic dust cloth for self-administered home allergen collection.

Most epidemiologic studies employ a vacuum cleaner used by a trained technician to collect household allergens. This approach is labor intensive, equipment dependent, and impractical if study subjects reside over a wide geographic area. We examined the feasibility of a self-administered dust collection method, using an electrostatic cloth sent by conventional mail, to obtain allergen measurements.

Twins as willing research participants: successes from studies nested within the California Twin Program.

The California Twin Program (CTP) is a population-based sample of over 52,000 twins in which a number of nested studies are ongoing. We outline our experience to date, providing estimates of crude response rates for a variety of different study designs and protocols. We have experienced very high response rates in our studies to date, even in studies with demanding protocols.

Interleukin-6-related genotypes, body mass index, and risk of multiple myeloma and plasmacytoma.

Interleukin-6 (IL-6) promotes normal plasma cell development and proliferation of myeloma cells in culture. We evaluated IL-6 genotypes and body mass index (BMI) in a case-control study of multiple myeloma and plasmacytoma. DNA samples and questionnaires were obtained from incident cases of multiple myeloma (n = 134) and plasmacytoma (n = 16; plasma cell neoplasms) ascertained from the Los Angeles County population-based cancer registry and from siblings or cousins of cases (family controls, n = 112) and population controls (n = 126).

Developing epidemic of melanoma in the Hispanic population of California.

Background: Hispanics comprise almost one-third of the population of California, are the most rapidly increasing racial/ethnic group in the state, and represent almost one-third of all Hispanics in the U.S. California has among the highest rates of melanoma in the world, yet little is known about trends in melanoma in its Hispanic population.

Th1 and Th2 cytokines and IgE levels in identical twins with varying levels of cigarette consumption.

Some have suggested that tobacco smoke may skew the immune system toward a Th2 pattern, however the effects of genetics or childhood exposures could explain these results. We compared PMBC supernatant or serum Th1 (INF-gamma) and Th2 (IL-4, IL-5, and IL-13) cytokine and IgE levels in members of 45 pairs of nonasthmatic monozygotic twins with varying levels of current cigarette consumption to determine if smoking was associated with Th1/Th2 function after accounting for genetic factors. A statistically significant dose-response was observed between levels of smoking and IL-13 (p=0.

The occurrence of chronic disease and other conditions in a large population-based cohort of native Californian twins.

We describe the prevalence of chronic diseases and conditions in a large cohort of twins, which has been developed to facilitate studies of the role of genetics and environment in the development of disease. The California Twin Program (CTP) comprises twins born in California between 1908 and 1982. Birth records from all multiple births (256,616 in total) were linked (multiple times between 1990 and 2001) with the California Department of Motor Vehicles (DMV) roster of licensees to obtain address information.