Photo by Petr Kratochvil
Results of a large study indicate that women who spend their leisure time sitting for prolonged periods—6 or more hours a day—have an increased risk of developing certain cancers.
These women had a significant increase in the risk of overall cancer, multiple myeloma, breast cancer, and ovarian cancer.
The increased risks were present even after taking into account a woman’s body mass index (BMI), frequency of physical activity, and other factors.
For men, there was no association between leisure time spent sitting and any type of cancer.
Alpa Patel, PhD, of the American Cancer Society in Atlanta, Georgia, and her colleagues conducted this research and reported the results in Cancer Epidemiology, Biomarkers & Prevention.
The researchers analyzed data on 69,260 men and 77,462 women who were initially cancer-free and enrolled in the American Cancer Society Cancer Prevention Study II Nutrition Cohort.
In addition to evaluating the amount of leisure time subjects spent sitting, the researchers assessed factors such as age, race, BMI, alcohol use, smoking status, diabetes status, diet, and frequency and type of physical activity.
At baseline, the men enrolled in this study were slightly older, leaner, and more likely to have ever smoked cigarettes compared to the women. Men and women who spent the most leisure time sitting were more likely than their peers to be obese, have type II diabetes mellitus or other chronic diseases, have a higher caloric intake, eat more red/processed meat, and have ever smoked.
Between 1992 and 2009, 18,555 men and 12,236 women were diagnosed with cancer.
In women, longer leisure time spent sitting was associated with a significantly increased risk of cancer overall, even after the researchers adjusted for potential confounders such as overall physical activity and BMI.
The relative risk (RR) of cancer was 1.10 for women who spent an average of 6 or more hours a day sitting, compared to those who spent less than 3 hours a day sitting.
Women who sat for 6 or more hours a day also had a significantly increased risk of multiple myeloma (RR=1.65), invasive breast cancer (RR=1.10), and ovarian cancer (RR=1.43).
Initially, there was a significant association between prolonged sitting and endometrial cancer, but this was attenuated after the researchers adjusted for BMI. The researchers also found positive, but not significant, associations between sitting time and esophageal, head and neck, and gallbladder cancers.
For men, there was no significant association between time spent sitting and overall cancer risk or the risk of individual cancers. The researchers said further study is warranted to better understand this difference between the sexes.
The team also noted that American Cancer Society guidelines for cancer prevention recommend reducing sitting time when possible. And, given the high rate of time spent sitting in the US, even a modest positive association with cancer could have broad public health implications.
