Nancy Swayne and Betsy Swayne-Oram still do not know their zygosity—whether they are identical or fraternal twins.
In hopes of one day finding out, the local twin pair frequently participates in research studies conducted by , which uses identical and fraternal twins to study the genetic and environmental factors relating to disease and vaccines.
"We do it because of the interest in our zygosity, the compensation. But also because of the interest in the study and the feeling that you're going to be helping somebody in the future," said Nancy, a 54-year-old Redwood City resident.
"It's always nice that something you're going to do will contribute to someone's health benefit," added Betsy, a Mountain View resident who is older than her sister by about five minutes (and has been known to boss Nancy around, fulfilling her role as older sister).
As part of SRI's Twin Research Registry, twins like the Swaynes get to participate in valuable medical research. They usually receive a bit of compensation (between $50 and $300, depending on the complexity of the study) and occasionally receive the research results — such as the result of their zygosity, an expensive procedure that many twins have not done.
"Twins are unique and special for research," said Dr. Gary Swan, the registry director who studies twins' responses to vaccines. "Twins are a really good way to help you at the beginning of molecular genetic investigations to sort out the relative importance of genetic and environmental factors."
One of the most interesting parts about Swan's work is when genetically identical twins do not respond the same way to vaccines. "You have to ask, why is there a discrepancy?" said Swan. "Is it due to environmental circumstances, or previous vaccination history, or other infections they once had?"
The ultimate goal is to develop more effective vaccines. "The assumption is that when you receive a vaccine, you're not immune to the disease — that's not always true," said Swan. Twin studies help learn what factors promote responses to vaccines.
SRI's Twin Research Registry is currently recruiting twins 40 years old and older for a study to help scientists develop more effective vaccines for chicken pox and shingles. Participants ages 50 and older will receive free Zostavax vaccines against herpes zoster, commonly known as shingles, a painful skin disease that can surface years after an episode of chicken pox.
Those who receive the vaccine then make four additional visits to monitor their immune response. Participants ages 40 to 49 will only require a single visit to donate a blood sample to the study.
SRI's twin registry, sought after by top universities like Stanford and the University of California, San Francisco, is nearly 3,000 members strong.
"The twins are wonderful about wanting to participate in research studies," said Lisa Jack, assistant director in the Policy Division at SRI. "We call them our 'angels.'"
Jack, Swan and their team of researchers are particularly interested in studying older adult twins - much of SRI's research asks to what extent changes with age are genetically determined - but they encourage twins of all ages, backgrounds, and health conditions to join the registry.
"If a twin pair is interested in being in the registry, all they're agreeing to do is to get a newsletter from us," said Swan. "Our role and responsibility is to update them on study opportunities, but they're not committed to any research."
The quarterly registry newsletter includes twin factoids, local twin profiles and information on upcoming studies. Members may choose to respond to questionnaires, come in to give blood samples, or otherwise participate in studies.
"The most interesting was the pain study," said Betsy, who discovered the registry seven years ago and encouraged her sister to join. "We had to hold a device that was heated against a leg or arm and let it sit on the arm until it was too painful to go further. They then administered a painkiller and tested the device again."
The pain study was the longest the twins had participated in, at five hours. Most studies take a couple of hours and pay $50 to $75 each.
"It wasn't scary at all," said Betsy. "The people were really neat and fun and informative to talk to." The Swayne twins' one regret is that SRI has not yet held a twin-wide event to help participating twins in the Bay Area meet other twins who share similar stories, like this one:
"One of the questions we get the most is, 'What is it like being twins?'" said Nancy. "We say, what's it like not being twins?"
Twins are part of a unique community, said Jack, who assists the three-to-five-year studies, sometimes two at once. Always on the lookout for new things to study, the Twin Research Registry often seeks twins' stories via its Facebook page and Twitter feed (@TwinSRI).
"We're always looking for more twins," said Jack. "We want it to be a community, we want everybody's input to be important."
If you and your twin are interested in participating in a local study, or receiving the international newsletter, visit the Twin Research Registry website or call 1-800-SRI-TWIN.