Category Archives: Current Studies

Study of Air Pollution in Twins (R33 phase)

This study seeks to understand how the environment influences our health by using a new device (the Portable Particle Monitor, PUWPM) that measures toxins in the environment, which was built and tested during the first phase of this study. These toxins include air pollution, noise, and allergens.

Exposure to particle pollution can result in increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days, especially for those with pre-existing heart or lung disease, older people, and children. The size of particles is directly linked to their potential for causing health problems. Fine particles (PM2.5) pose the greatest health risk. The following is an example of what we are able to observe from collected data. Both maps show a morning walk in the summer. However, the walk on the right took place after major forest fires had broken out in the greater Pacific Northwest area. We can see that the PM2.5 this individual was exposed to was much lower before the fires broke out (map on left). By comparing twins, we can better understand how exposures to toxins in the unique environment may influence health.

Identical twins living apart within the State of Washington will be considered for this study. Eligible pairs will come to the Roosevelt Clinic in the University District of Seattle to receive the study materials. The study coordinator will record vital measurements and conduct a spirometry (lung function) test. At the end of the visit, participants will have their blood drawn. Biological specimens will be used to measure the amount of inflammation in the body, which may be related to environmental exposures. Data is then collected at home for two weeks. Participants will carry a GPS and wear an activity monitor that is similar to a pedometer or a Fitbit, as well as carry the PUWPM from the time they wake up until they go to sleep at night. They will also complete questionnaires. At the end of the two-week period, everything is returned to the study coordinator in a prepaid FedEx box.

Physical Activity in Twins (PAT) follow-up study

This study continues on work conducted from 2012-15 exploring 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 and health is not fully understood.

In this follow-up study, twin pairs who participated in the PAT study are contacted to participate in one week of follow-up data collection. All data collection is done entirely at home, and participants do not have to live within the Puget Sound to be eligible. Participants wear a GPS and an activity monitor, and complete questionnaires.

Gene Expression and the Microbiome in Twins (GEMsTone)

Cells in the human body contain DNA. Each cell expresses, or turns on, a fraction of its genes in a process known as gene regulation. Genes can be expressed depending on your genetic history, your lifestyle, and your environment. Microbes are very small life forms such as bacteria that exist on or in the human body. The human microbiome is the full collection of genes of all of the microbes. In this study, we are interested in learning more about the relationship between your genes and your microbiome. The gut microbiome changes over time, but can also change when your diet changes or when your health in general changes. As a twin and a member of the WSTR, you can make a unique contribution to understanding the relationship between the gut microbiome and gene expression.

Eligible twin pairs are sent the collection materials to collect data at home. Data collection materials include three questionnaires, measuring waist circumference, using a soft brush to collect buccal (cheek) cells for epigenetic analysis, and collecting a stool sample for the gut microbiome analysis.

Twin Breast Cancer Study

Dr. Thomas Mack of the USC California Twin Program is reaching out to twins diagnosed with breast cancer in order to understand why some women remain free from breast cancer when other women with the same genetics and upbringing are affected.

What we know:
  • As a group, twin women of any age, including identical twin women, are at the same risk of breast cancer as their friends and neighbors.
  • Even though inheritance seems to play at least some role in most cases of breast cancer, most of the healthy co-twins of women who are diagnosed with breast cancer remain free, for years, decades or permanently.
  • That suggests that some causal elements are acquired, probably long before the appearance of the disease, possibly as early as childhood.
What does the study entail?

We will ask each participant to provide a sample of saliva. From such samples we can find cells containing the unique inherited DNA code and identify any genetic breast cancer risk factors.

What questions will be asked?
  1. Generally: Participants will be asked questions relating to known predictors of breast cancer risk, most of which relate to reproductive history.
  2. Twin comparisons: Twins have compared each other since childhood, and are uniquely able to recall and agree on early differences, even after decades. Questions will be especially directed at early differences.
  3. We will ask breast cancer cases to help us obtain Pathology Reports and samples of tumor tissue from providers.

The questions should take you one-half to one hour. The more twins who participate, especially as pairs, the more likely that we can find answers to these important questions about a dreaded disease.

The study is supported by the National Cancer Institute of the National Institutes of Health. There is no cost to volunteers, except the time it takes to mark your responses and send your specimen. You will never be asked for money (your cooperation is more valuable). You may always refuse to answer any question, and you may withdraw cooperation at any time. All information will be held in complete confidence. No outside persons will have access to your identity without your permission. Results will only be released in statistical form, and no persons will ever be identified.


Click here to send an email to the study coordinator. If you would prefer to speak to someone by phone, please call 1-323-865-0828.

New Study Opportunity


A research group at the University of Washington is seeking identical twins ages 9 to 14 for an exciting new brain imaging study!

Twins will have their brains scanned while they engage in computer coding tasks. Twin participants will receive a print out of their brain scan, and parents will receive a written assessment report regarding their children’s cognitive, oral language, reading, writing, and math skills.

Twins must be right handed and not wear braces or other metal that cannot be removed. Children do not have to have prior experience in computer coding in order to participate. Interested parents should contact the staff psychologist Dr. Cheryl Yates at to make a phone appointment to explain the study and schedule an assessment/imaging session if interested.

Study of Air Pollution in Twins (R21 phase)

This study seeks to understand how the environment influences our health by testing a new device that will measure toxins in the environment. These toxins include air pollution, noise, and allergens. This study includes 2 waves, with the potential for a third. For the first wave, twins will come to our office in downtown Seattle to receive the devices and instructions for use. The in-person visit also includes collecting height and weight measurements. Data is collected at home for one week. At the end of the week, twins will return to our office to participate in an in-person focus group with 2-3 other pairs of twins. Based on the feedback that we receive, we will make changes to the devices, which we expect to take about 6 months. For wave 2, we will send updated study devices and have twins collect data for an additional week. At the end of wave 2, study materials are sent back to us, and twins will participate in an online Skype session with 2-3 other pairs of twins. If a third wave is necessary, it will be completed in the same way as the second.

Published research from this study

Mood and Methylation in Twins

While identical twins are born with the same set of genes, their lifetime experiences (environment) may differ. These environmental differences may cause small changes in how their genes are regulated (turned on or off). Such changes are called epigenetic modifications. One type of epigenetic modification is called DNA methylation.

This study is recruiting identical twin pairs who differ in their mood histories: one twin has had persistent feelings of sadness or emptiness, and/or loss of interest or motivation at any time in their life, while the other twin has no history of these experiences. DNA methylation will be analyzed to see what differences there are between the twins.  Some goals of the study are to better understand how gene regulation may affect mood experiences such as sadness or lack or motivation, and to increase knowledge about how your environment may affect your behavior and health.

Each potential study participant will have a phone interview. If both twins are a good fit for the study and choose to participate, they will do study procedures at home and have a one-hour in-person visit to the University of Washington Medical Center in Seattle. The at-home procedures are completing questionnaires and collecting samples of saliva, stool and toenail clippings. The in-person visit includes a blood draw, urine sample collection, physical measurements, and completing questionnaires.

Published research from this study

Brain Regulation of Appetite in Twins (BRAT)

The goal of this study is to learn more about the regulation of appetite, in order to better understand how the central nervous system regulates appetite and food consumption.

This study required both members of the twin pair to come to the University of Washington Medical Center together for one eight-hour visit.  Blood samples were collected over the course of the 8-hour visit.  Participants were also be asked to complete questionnaires, have a DEXA scan (a type of x-ray), and have MRI scans.

Initial results from the study showed that body mass index (BMI) was highly correlated within twin pairs. Twin pairs were also similar in meal-induced changes in hunger, fullness, and appeal of fattening foods. These findings suggest that there is a genetic component to satiety perception (fullness after eating) and the effect of a meal in altering regional brain responses to images of food.

Another finding showed that anxiety in women may promote excess calorie consumption, placing women with a genetic predisposition to weight gain at a risk of obesity.

Published Research