The message is everywhere: Exercising and staying at a healthy weight can cut the 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.

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.

The grant will enable scientists to delve deeper into the lifestyle and genetic factors that may influence cancer risk — and provide evidence for public health efforts that may potentially help millions.

The California Teachers Study includes nearly 133,500 female teachers and administrators in the California public schools’ retirement system. Researchers began following the study participants in 1995, periodically monitoring their health status and height and weight. They also ask about their habits, including their exercise patterns and use of alcohol and hormone replacement therapy, oral contraceptives and other drugs.

Because researchers have access to California’s statewide cancer registry and hospitalization data, they can obtain important health information, such as cancer diagnoses, births and surgeries, related to their study participants. The combination of data about risk factors and health outcomes over a long period makes the study particularly powerful.

“In the next five years, the California Teachers Study will allow us to learn much more about how variations in women’s genes interact with these lifestyle factors to influence risk,” Bernstein said.

The researchers will focus on three areas of societal change: physical activity, obesity and aspirin use.

Physical Activity

People worldwide are becoming less physically active, their once-active hobbies replaced by TV viewing and Internet surfing Yet researchers have shown that getting plenty of exercise can reduce risk of breast and colon cancer — as well as other problems such as cardiovascular disease and diabetes — so health experts recommend regular physical activity. According to Bernstein, exercise participation and benefits from these activities might be linked to variations in certain genes associated with fitness, endurance and athletic ability. Through the study, researchers will examine the relationship between these gene variants, physical activity and breast cancer risk — a topic that has never been studied.

Obesity

Obesity rates are soaring, which likely increases future cancer rates, too. California Teachers Study scientists will look at patterns of changes in body fat over a lifetime and how being obese is associated with common forms of breast, endometrial and colon cancers. Disease risk stems from more than obesity, so the researchers also will investigate how other cancer risk factors such as physical activity, hormone therapy and oral contraceptive use, eating and drinking habits, diabetes, smoking and menopausal status can modify relationships between obesity and these cancers.

Aspirin Use

Drugs such as tamoxifen help prevent breast cancer among breast cancer survivors and women at high risk for the disease, but offer little benefit for average women. They need other options that are safe, simple and inexpensive. One possibility is aspirin.

Many women already take low doses of aspirin to cut their risk of cardiovascular disease, so California Teachers Study researchers will examine whether this aspirin use can modify breast cancer risk linked to use of hormone therapy and other factors, and if it has effects on any subtype of breast cancer in particular.

The researchers also will examine whether variants in genes related to inflammation, immune function and insulin resistance interact with aspirin use, obesity or physical activity to influence breast cancer risk.

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