Abstract A36: Recreational physical activity and the risk of pancreatic cancer in the California Teachers Study
Authors: Togawa Kayo , Ma Huiyan , Sullivan-Halley Jane , Clague Jessica , Neuhausen Susan , Lee Eunjung , Deapen Dennis , Bernstein Leslie 
Published: October 2015

Background: Pancreatic cancer is highly fatal; thus, preventive strategies are needed. Besides cessation of cigarette smoking, physical activity may reduce pancreatic cancer risk by improving insulin sensitivity and glucose tolerance. However, the existing data lack consistency and generally, physical activity has been measured only at one time point. We examined recreational physical activity during different periods of life as well as a cumulative, long-term physical activity measure in relation to the risk of pancreatic cancer in California Teachers Study (CTS).

Methods: 120,921 women aged 22-84 years participating in the CTS with no history of pancreatic cancer were followed from 1995 through 2011. The self-administered baseline (1995-1996) questionnaire captured information on demographics, moderate and strenuous recreational physical activity during high school, between ages 18 and 24, 25 and 34, 35 and 44, and 45 and 54 years, and in the three years before baseline, and potential risk factors for pancreatic cancer such as body mass index (BMI), diabetes, alcohol consumption, cigarette smoking, and dietary fat intake. Incident diagnoses of invasive pancreatic cancer were identified through annual linkages with the California Cancer Registry. We calculated average number of hours per week for recreational physical activity during different periods of life and combined them into a long-term physical activity measure. We fit Cox proportional hazards models to data to estimate the hazard ratios (HR) of pancreatic cancer risk and their corresponding 95% confidence intervals (CI) associated with moderate and strenuous physical activity in each age/time period and over the “long-term.” For each analysis, the least active group (≤0.5 hours/week) served as the reference group. Multivariable models were stratified by age at baseline (in single years) and were adjusted for race, total pack-years of cigarette smoking, alcohol consumption and total dietary fat intake in the year before baseline, diabetes, and BMI at baseline. Furthermore, we tested for a linear trend in risk by fitting the median value of physical activity within each category; we also examined whether BMI, smoking status, and alcohol intake modified any physical activity association.

Results: During 1,715,690 person-years of follow-up, 429 women were diagnosed with invasive pancreatic cancer. The average age at diagnosis of pancreatic cancer was 74 years. In the multivariable model, women with higher levels of long-term moderate/strenuous physical activity had lower risk of pancreatic cancer than the least active women (≤0.5 hours/week) although the 95% CI included one (2.51-5.5 hours/week: HR=0.76; 95% CI=0.56-1.02, &gt;5.5 hours/week: HR=0.85; 95% CI=0.63-1.15) and no linear trend in pancreatic cancer risk was observed (Ptrend=0.35). In the analysis of physical activity during different periods of life, we observed a marginally significant decreasing trend in risk with increasing physical activity during ages 18-24 years (Ptrend=0.05). The stratified analysis indicated a decreasing trend in pancreatic cancer risk with increasing physical activity during ages 18-24 years among women who were overweight or obese at baseline (Ptrend=0.006), who never smoked cigarettes (Ptrend=0.02), and who consumed &lt;10 grams of alcohol per day in the year before baseline (Ptrend=0.02). No significant effect modifications were observed.

Conclusions: The CTS data suggest that a higher level of recreational physical activity in early adulthood modestly reduces the risk of pancreatic cancer development in subgroups of women. However, we lacked sufficient statistical power to demonstrate effect modification. Larger studies are needed to understand whether the effect of physical activity on pancreatic cancer varies by age at activity, BMI, smoking status, or alcohol intake.

Citation Format: Kayo Togawa, Huiyan Ma, Jane Sullivan-Halley, Jessica Clague, Susan Neuhausen, Eunjung Lee, Dennis Deapen, Leslie Bernstein. Recreational physical activity and the risk of pancreatic cancer in the California Teachers Study. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr A36.