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Skip Navigation LinksGenome Wide Association Studies (GWAS)

GWAS circos representationGenome Wide Association Studies (GWAS)

When you joined the Women’s Health Initiative many years ago, you may recall providing blood samples at your clinical center visits. By the end of the original phase of the study, over 3 million blood samples had been collected and stored in freezers! Those specimens are adding to our knowledge about women’s health and disease in many important new ways. One of the most significant ways may come from using those stored blood samples as part of a Genome Wide Association Study, or “GWAS” for short. A GWAS is a study that looks at the DNA of WHI participants by using the specimens of those who consented to having their blood used in genetic studies. These studies (which do not link your blood to your identity) may help scientists find out what genetic factors are associated with diseases such as diabetes, hypertension, heart disease, osteoporosis, cancer, and dementia.

What is the purpose of a GWAS?

The WHI GWAS examines the genome, which is the individual’s complete set of DNA, of women who have participated in WHI to see if there are genetic variations associated with a particular disease. To do this, the genomes of women with a particular disease are compared to similar women without the disease. If certain genetic variations are seen in participants with the disease compared to those without, the variations are said to be "associated" with the disease. The genetic variations themselves do not necessarily cause the disease, but may put individuals with the variant at increased risk. Other influences (diet, smoking, environment) may also be important factors that work along with genetic  variations to influence risk. Once new genetic associations are identified, it may be possible to use the information to detect, treat, and prevent the disease. We hope to learn much more about this using the WHI blood samples.

Is each person’s genome unique?

Humans come in many shapes and sizes, but we’re all very similar at the genome level. In fact, the genomes of any two people are more than 99% the same. However, the tiny fraction of the genome that varies among humans is what makes each person unique, for example, in terms of characteristics such as eye, skin, and hair color. These types of variations also influence the risk for developing certain diseases. We hope to learn more on how these variations influence which women get certain diseases and which women do not.

Is everything determined by my DNA?

No, DNA is just one piece of the puzzle. When it comes to your health, lifestyle and environmental factors, such as the food you eat and pollutants in the air you breathe, may also play a role. Once we learn more about how genomes interact with these lifestyle and environmental factors to cause disease, we may be able to change our lifestyle habits or adapt our environment to lower our risk. Since we get our DNA from our parents, risk of certain diseases and other characteristics run in families. For most common diseases, such as cancer, diabetes, and heart disease, researchers are finding that multiple genes—along with lifestyle and environmental factors—work together to determine the risk of these and other disorders.

What will genome research mean for me?

Over time, genetic tests may become available to predict risk for developing many common health conditions. Based on the information contained in a person’s genome, healthcare providers may be able to develop strategies that are more specific to you for detecting, treating, and preventing disease. For example, if a genetic profile shows that you are at increased risk for colon cancer, you might undergo more frequent colonoscopy screening or be asked to make certain dietary changes.


Genetic studies help us understand the link between genes and certain diseases. This research is in progress, and already includes health studies looking at genetic variations associated with:

  • health of African American and Hispanic women who joined WHI

  • health outcomes of women who were in the Hormone Therapy program

  • risk of hip fractures

  • risk of pancreatic and other less common cancers

  • risk of colorectal cancer

  • risk of strokes

  • gene-environment interactions

  • memory and memory decline

As time goes on, many other associations will be tested, including those factors associated with healthy aspects of aging. The blood samples you provided early in the study, as well as the information you provided over the years and continue to provide annually through the mailed questionnaires, are helping scientists make major contributions to this growing area of research. We really appreciate all you’ve given and continue to give as an ongoing participant in the WHI!