The message is everywhere: Exercise and stay at a healthy weight to cut your risk of cancer and other diseases. But do these steps pay off equally for everyone? What else can women do to improve their chances?

The experiences of hundreds of thousands of California women, documented through more than a decade’s worth of research, will help answer those sticky questions.

Leslie Bernstein is principal investigator on the influential California Teachers Study. (Photo by Walter Urie)

Led by Leslie Bernstein, Ph.D., director of City of Hope’s Division of Cancer Etiology, the California Teachers Study has shown how obesity, physical activity, diet and use of medications can influence women’s risk of breast and other cancers. Now, thanks to a new, $16.8 million grant from the National Cancer Institute, the study will uncover even more lessons about lifestyle and health.

Scientists will go deeper — not only into the steps women can take to reduce their risk, but also into how women’s genes might play a part. They hope their findings provide evidence for public health efforts that could help millions.

The study includes nearly 133,500 female teachers and administrators in the California public schools’ retirement system. Researchers started following them in 1995, asking them about their health status, height, weight and habits. Women have regularly provided a window into their lives, sharing information such as how much they exercise, whether they drink alcohol and if they used hormone therapy, oral contraceptives or other drugs.

In the coming years, researchers will home in on three areas that have seen a lot of change: women’s physical activity levels, obesity and aspirin use.

Exercise

Getting plenty of exercise reduces the risk of breast and colon cancer, and potentially other cancers, too. But does everyone get the same benefit from a walk, jog or tennis class? According to Bernstein, certain genes associated with fitness, endurance and athletic ability might actually affect the benefit exercise provides to each woman — and whether women are physically active in the first place.

Obesity

Many women today are struggling to lose their extra pounds. Obesity rates are rising, likely increasing future cancer rates, as well. Under the California Teachers Study, scientists will look at patterns of changes in body fat over a lifetime and how being obese or overweight is associated with common forms of breast, endometrial and colon cancers.

Disease risk stems from more than obesity, though. The researchers also will investigate how other factors like physical activity, hormone therapy and oral contraceptive use, eating and drinking habits, diabetes, smoking and menopausal status can interact with obesity to affect cancer risk.

Aspirin

Physicians today offer drugs like tamoxifen to help prevent breast cancer among breast cancer survivors and women at high risk for the disease, but these drugs offer little benefit for the average woman. They need options that are safe and inexpensive, and one possibility is aspirin.

Many women already take children’s aspirin to cut their risk of heart disease. With that in mind, the scientists hope to see whether aspirin can reduce breast cancer risk linked to the use of hormone therapy and other factors, and if it has effects on any type of breast cancer in particular.

Variations in genes related to inflammation, immune function and insulin resistance might also affect how aspirin use, obesity or physical activity influence breast cancer risk.

“We’re excited about this work, because we will be looking at risk factors that are modifiable,” Bernstein said. “These are steps that could help prevent cancer population-wide.”