Completed Studies

Physical Activity in Twins (PAT)

This study explored the role of the built environment in supporting healthy lifestyles. The built environment is defined as human-made surroundings, such as buildings, streets, and transportation systems, which support or hinder human activity. Although this topic has gained increasing attention from many researchers over the last several years, the influence of the  environment on behaviors […]

HSV Pilot

Oral herpes is a very common infection of the mouth area. It is caused by the herpes simplex virus type-1 (HSV-1). When they are first infected, some people have symptoms while others do not.  After the first infection, the virus becomes dormant (goes to sleep) in nerve tissues in the face for life.  Periodically the […]

Brain regulation of appetite in twins

Background: Neural responses to highly energetic food cues are robust and are suppressed by eating. It is not known if neural responsiveness to food cues is an inherited trait and possibly even one that mediates the genetic influences on body weight that have been previously observed. Objective: We investigated the inherited influence on brain responses to high-calorie […]

Familial Contributions to Self-Reported Sleep and Pain in Female Twins

Objective: The relationship between sleep quality and pain has been studied in populations with chronic pain and in nonclinical populations using experimental paradigms. Little is known about the familial contributions to this relationship. This study examines self-reported sleep quality and pain in a nonclinical sample and to explore familial (i.e., shared genetic and common family environment) […]

Allergy & Asthma in Twins

This study is being conducted by Dr. Kari Nadeau, an allergist and immunologist at Stanford University, and Dr. Rebecca Bauer, a postdoctoral researcher in Dr. Nadeau’s laboratory. The purpose of this study is to better understand how exposure to tobacco smoke affects immunity and diseases of the immune system such as asthma. Researchers will assess […]

Mitochondrial DNA Copy Number in Sleep Duration Discordant Monozygotic Twins

Study objectives: Mitochondrial DNA (mtDNA) copy number is an important component of mitochondrial function and varies with age, disease, and environmental factors. We aimed to determine whether mtDNA copy number varies with habitual differences in sleep duration within pairs of monozygotic twins. Setting: Academic clinical research center. Participants: 15 sleep duration discordant monozygotic twin pairs (30 twins, 80% […]

In adult twins, visceral fat accumulation depends more on exceeding sex-specific adiposity thresholds than on genetics

Objective: We recently reported sex-specific percent body fat (%BF) thresholds (males=23%, females=38%) above which, visceral adipose tissue (VAT) significantly increases. Using monozygotic (MZ) and dizygotic (DZ) twins, we examined the influence of genetics on regional fat distribution measured by dual-energy X-ray absorptiometry, above and below these sex-specific thresholds for VAT accumulation. Methods: Fifty-eight twin pairs (44 MZ, […]

Heritability of Pain Catastrophizing and Associations with Experimental Pain Outcomes: A Twin Study

This study used a twin paradigm to examine genetic and environmental contributions to pain catastrophizing and the observed association between pain catastrophizing and cold-pressor task (CPT) outcomes. Male and female monozygotic (n = 206) and dizygotic twins (n = 194) from the University of Washington Twin Registry completed a measure of pain catastrophizing and performed […]

Clinical and evoked pain, personality traits, and emotional states: Can familial confounding explain the associations?

Objectives: Pain is a complex phenomenon influenced by context and person-specific factors. Affective dimensions of pain involve both enduring personality traits and fleeting emotional states. We examined how personality traits and emotional states are linked with clinical and evoked pain in a twin sample. Methods: 99 female twin pairs were evaluated for clinical and evoked pain using […]

Stepping towards causation in studies of neighborhood and environmental effects: How twin research can overcome problems of selection and reverse causation

No causal evidence is available to translate associations between neighborhood characteristics and health outcomes into beneficial changes to built environments. Observed associations may be causal or result from uncontrolled confounds related to family upbringing. Twin designs can help neighborhood effects studies overcome selection and reverse causation problems in specifying causal mechanisms. Beyond quantifying genetic effects […]

A twin study of differences in the response of plasma ghrelin to a milkshake preload in restrained eaters

Background: Genetic, physiological, and psychological factors can affect food intake, but twin studies can distinguish inherited from environmental contributors. We examined the influence of attempted cognitive control of eating (“restrained eating”) on levels of appetite-regulating hormones. Methods: Sixteen female, monozygotic twin pairs, discordant for Restraint Scale score (i.e., one twin a restrained eater with score>15 whereas the […]

Salivary cortisol and cold pain sensitivity in female twins

Background: There is a dearth of knowledge about the link between cortisol and pain sensitivity. Purpose: We examined the association of salivary cortisol with indices of cold pain sensitivity in 198 female twins and explored the role of familial confounding. Methods: Three-day saliva samples were collected for cortisol levels and a cold pressor test was used to collect […]

Emerging technologies for assessing physical activity behaviors in space and time

Precise measurement of physical activity is important for health research, providing a better understanding of activity location, type, duration, and intensity. This article describes a novel suite of tools to measure and analyze physical activity behaviors in spatial epidemiology research. We use individual-level, high-resolution, objective data collected in a space-time framework to investigate built and […]

Adverse childhood experiences, health perception, and the role of shared familial factors in adult twins

To examine the relationship between adverse childhood experiences (ACE) and health perception in adulthood, and to explore the contribution of shared familial factors to these associations. Data were collected from 180 female twins (90 pairs) from the community-based University of Washington Twin Registry. Participants completed questionnaires including the modified ACE Questionnaire, Traumatic Life Events Questionnaire, […]

Acquired differences in brain responses among monozygotic twins discordant for restrained eating

We studied whether self-reported intent to exert cognitive control over eating was associated with differences in brain response to food cues, independent of genetic background. Subjects were ten pairs of identical twins in which one twin was a restrained eater and the co-twin was unrestrained, as classified by the Herman and Polivy Restraint Scale. Before […]

C-Reactive Protein and Pain Sensitivity: Findings from Female Twins

Background: Systemic inflammation and pain sensitivity may contribute to the development and maintenance of chronic pain conditions. Purpose: We examined the relationship between systemic inflammation as measured by C-reactive protein (CRP) and cold pain sensitivity in 198 female twins from the University of Washington Twin Registry. We also explored the potential role of familial factors in this […]