Inactivity's Links to Longevity, Cancer Risk and Health
The growing body of research on how activity – and inactivity – affects cancer risk and overall health has gotten a lot clearer this month with the release of several notable studies. It may make you want to walk around as you read.
10% of two cancers
Worldwide, one in ten cases of both breast cancer and colon cancer is due to a lack of physical activity, with inactivity as much to blame for the major non-communicable diseases as smoking or obesity, concluded an analysis published in The Lancet last week.
The analysis quantified the effects of physical inactivity on heart disease, type 2 diabetes, and breast and colon cancers. Physical inactivity was defined as not meeting the World Health Organization guidelines, which match US guidelines: Adults should get at least 150 minutes of moderate-intensity aerobic activity each week, with muscle strengthening activities at least two days a week.
“This is important science,” says Christine Friedenreich, PhD, of Alberta Health Services-Cancer Care, a leading researcher on the activity-cancer link who also spoke at last year’s AICR Annual Conference. “The Lancet team applied a lot of rigor, and these estimates are solid. And as the authors point out, these numbers likely represent the lower threshold of how many cancers could be prevented by becoming more active.”
The study determined that physical inactivity causes 6 percent of coronary heart disease; 7 percent of type 2 diabetes; 10 percent of breast cancers; and 10 percent of colon cancers. Together, inactivity caused more than 5.3 million of the 57 million deaths that occurred worldwide in 2008.
The authors concluded that if the population as a whole were only 10 percent more active, this would prevent more than 533,000 deaths every year; if the population was 25 percent more active, the world would prevent more than 1.3 million deaths each year.
It was good to see cancer included in the list of non-communicable diseases studied, notes Friedenreich, who was among a small group of scientists studying this topic. “Before, cancer was left off that list. Now cancer is accepted as one of the extremely important non-communicable diseases related to physical activity."
Sitting lowers life expectancy
If inactivity links to increased risk of disease, can inactivity also affect life expectancy? Yes, finds an analysis of research published in the journal BMJ Open.
Cutting the amount of time we sit to fewer than three hours every day may add 2 years to the US life expectancy of adults. And reducing TV viewing to less than two hours every day might extend life by almost 1.4 years. Watching TV is a recognized measure of sedentary behavior.
For the study, researchers pulled data from the National Health and Nutrition Examination Survey (NHANES) for 2005/6 and 2009/10, to determine the amount of time US adults spent watching TV and sitting down on a daily basis. They then applied population studies on sitting time and deaths, taking into account age and sex.
This finding applies to the US population, not individuals, the authors caution.
“Before, cancer was left off that list. Now cancer is accepted as one of the extremely important non-communicable diseases related to physical activity."
Activity for lower breast cancer risk
AICR’s expert report and its updates link relatively high levels of physical activity to decreased risk of postmenopausal breast cancer. A new study published in Cancer now suggests that any intensity level of physical activity – before or after menopause – may reduce breast cancer risk. Substantial weight gain appeared to negate the benefits.
The study included approximately 3,000 women who were ages 20 to 98. About half of the women had breast cancer.
Women who exercised either during their reproductive or postmenopausal years had a reduced risk of developing breast cancer. Women who exercised 10 to 19 hours per week experienced the greatest benefit with an approximate 30 percent reduced risk, but lower amounts also were slightly protective. Risk reductions were observed at all intensity levels.
The study also found that even active women who gained a significant amount of weight – particularly after menopause – had an increased risk of developing breast cancer, indicating the importance of staying a healthy weight.
"This study provides further evidence that being physically active is associated with lower risk for breast cancer after menopause," said Patrick Bradshaw, an epidemiologist at the University of North Carolina and a Marilyn Gentry Fellow who is one of the study's authors. The majority of breast cancer is diagnosed in postmenopausal women. "What's really interesting is that the relationship was consistent when different times of physical activity were considered, during reproductive years and after menopause. This would seem to say that it's never too late to reap the benefits of being active."
Along with postmenopausal breast cancer, AICR’s expert report and its updates link physical activity to decreased risk of colorectal and endometrial cancers. The reports also find that watching too much television and being sedentary increases the risk of weight gain and obesity, which is linked to increased risk of seven types of cancer.
“The research is emerging on sedentary behavior but we already know that physical activity has quite a big impact on cancers,” said AICR Director of Research Susan Higginbotham, PhD, RD. Activity is one part of a healthy lifestyle shown to lower cancer risk. “A healthy diet, staying at a healthy weight and not smoking, those factors work together – as soon as you start combining them, cancer risk drops even further.”
- I-Min Lee et al. “Effect of physical inactivity on major non-communicable diseases worldwide: an analysis of burden of disease and life expectancy.” The Lancet, Volume 380, Issue 9838.
- Katzmarzyk PT, Lee IM. “Sedentary behaviour and life expectancy in the USA: a cause-deleted life table analysis.” BMJ Open. 2012 Jul 9;2(4).
- Lauren E. McCullough et al. Fat or Fit: The Joint Effects of PA, Weight Gain and Body Size on Breast Cancer Risk. Cancer, Published online June 25, 2012.
- Garber CE, Blissmer B, Deschenes MR, Franklin BA, Lamonte MJ, Lee IM, Nieman DC, Swain DP. American College of Sports Medicine position stand. Quantity and quality of exercise for developing and maintaining cardiorespiratory, musculoskeletal, and neuromotor fitness in apparently healthy adults: guidance for prescribing exercise. Med Sci Sports Exerc. 2011 Jul;43(7):1334-59.