Twin study sheds light on how lifestyle and environment affect health – WSU Insider

Many people’s best ideas may come in the shower, but for Dedra Buchwald — director of the WSU Institute for Research and Education to Advance Community Health — a stroke of research genius struck her at the local driver’s license office nearly 25 years ago. A professor of medicine at the University of Washington at the time, Buchwald had gone to replace a lost driver’s license. As she filled out a form, a question caught her eye, “Are you a twin or a triplet?”

At the time, Washington driver’s license numbers were generated based on a combination of characters representing the applicant’s name and date of birth. This meant that twins with similar names could end up with identical numbers, so asking the question allowed the licensing department to avoid duplicate numbers. For Buchwald, it provided an opportunity to work with the state to create an invaluable resource that didn’t yet exist here: a dual research registry.

Now led by Glenn Duncan, the Elson S. Floyd College of Medicine professor and chair of the Department of Nutrition and Exercise Physiology, the Washington State Twin Registry includes thousands of twin pairs. Based on the twins’ responses to an initial enrollment survey and regular follow-up surveys, Duncan and his team are using data from the registry to examine the relationship between people’s lifestyle behaviors and living environments and their physical and mental health.

Studying these complex questions in twins allows researchers to draw conclusions with a greater degree of certainty than they could if studying unrelated individuals.

“In any study, when you look at associations between behaviors and outcomes, you don’t know if what you’re seeing is just a correlation or if there’s actually a causal relationship between the two,” Duncan said. “By doing our research in twins – which share 100 percent of the genes for identical twins and 50 percent of the genes for fraternal twins – we can control for their shared genetics as well as the fact that they were raised in a common environment. This allows us to increase our confidence that the associations we see are real and not just statistical artifacts.

During the COVID pandemic, the twin registry allowed them to conduct timely research on the effects of pandemic measures on physical and mental health. This includes studies on how changes in physical activity levels during stay-at-home orders affect stress and anxiety, the impact of lockdown on alcohol use and mental health effects on sleep.

In a more recent study of more than 6,000 twin pairs, Duncan and his team analyzed the links between five key lifestyle behaviors and body mass index (BMI) and symptoms of depression. The behaviors included in the study were sleeping 8 or more hours a night, eating 5 or more servings of fruits and vegetables a day, spending a maximum of 2 hours a day sitting, getting at least 150 minutes of physical activity a week, and not smoking .

“Given that it’s very difficult for anyone to meet all five of these standards, what we really wanted to clarify is which of these behaviors, alone or in combination, have the greatest impact on these overall health outcomes.” , Duncan said. “What we found is that meeting standards of moderate to vigorous physical activity and levels of time spent sitting seem to be most important for BMI, and spending little time sitting and not smoking seem to have the most -a powerful influence on depressive symptoms.”

Based on data collected at one point in time, their findings suggest a need for researchers to conduct longitudinal studies in a more diverse population of twins to establish potential causal relationships between these behaviors and outcomes. This can help those struggling to meet multiple health standards know which behaviors to prioritize to increase their chances of successfully combating obesity and depression.

Pending funding, the next big project Duncan’s team hopes to tackle will look at how people’s living environments affect the rate at which they age.

“There is a lot of evidence to suggest that people age differently and that your age on the calendar may not mean as much as we thought,” he said. “Our plan is to analyze existing DNA samples collected more than a decade ago, along with newly collected samples from the same twin pairs, determining their biological rather than chronological aging trajectories and relating them to measures of their cognitive function.” Ultimately, what we hope to uncover is what factors—such as whether or not you live in a disadvantaged area—actually accelerate your biological age, independent of individual risk factors.

For more information about the Washington State Twin Registry, visit

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