The analysis of data from more than 1,500 cancer survivors also revealed that being physically active was associated with a much lower risk of cancer-specific death, researchers report in JAMA Oncology.
"The combination of prolonged sitting with lack of physical activity was highly prevalent among U.S. cancer survivors, and this sedentary lifestyle was associated with worsened survival," said coauthors Chao Cao and Dr. Lin Yang with Alberta Health Services in Calgary, Canada.
"The exact biologic mechanisms are unclear but the negative effects on metabolic and sex hormones, inflammation, and immunity are some of the main hypothesized pathways," they told Reuters Health in a joint email. "Experimental studies have shown that uninterrupted sitting for long periods is associated with impaired glucose metabolism and increased systematic inflammation, and these can be attenuated by breaking up prolonged sitting."
To take a closer look at the impacts of long hours spent sitting and little exercise, the two researchers and a colleague turned to a nationally representative sample from the U.S. National Center for Health Statistics' National Health and Nutrition Examination Survey (NHANES), which has been conducted on biennially since 1999.
NHANES collected cancer information - including cancer type and age at diagnosis - during in-person interviews. Participants were asked "Have you ever been told by a doctor or other health professional that you had cancer or a malignancy of any kind?" Those who responded yes were defined as cancer survivors and were asked, "What kind of cancer was it?" and "How old were you when this cancer was first diagnosed?"
The participants reported their total daily sitting time and their leisure-time physical activity (LTPA) through the Global Physical Activity Questionnaire (GPAQ). They were also asked about moderate- and vigorous-intensity recreational activities during the in-person interviews.
The researchers defined LTPA as minutes of moderate-intensity recreational activities plus twice the minutes of vigorous intensity recreational activities. They linked participants' NHANES data to mortality data from the National Center for Health Statistics.
The analysis was based on data from 1,535 cancer survivors; 57% reported an LTPA of 0 minutes per week during the previous week (inactive group); 16% reported an LTPA of less than 150 minutes per week (insufficiently active group); and 28% reported an LTPA of 150 minutes or more per week (active group).
Thirty-five percent reported sitting for six to eight hours per day and 25% reported sitting for than eight hours per day. During the follow-up period of up to nine years (median, 4.5 years), 293 of the cancer survivors died, 114 from cancer, 41 from heart diseases and 138 from other causes.
On multivariable analysis, the risks of both all-cause death (hazard ratio, 0.34) and cancer-specific death (HR, 0.32) were significantly lower in physically active people than in the inactive group.
More sitting, on the other hand, was quite deleterious. Sitting more than eight hours a day was associated with significantly higher risks of all-cause mortality (HR, 1.81) and cancer death (HR, 2.27) compared with sitting less than four hours a day.
When the researchers looked at the combined effects of sitting time and amount of physical activity, they found that inactive and insufficiently active survivors who reported sitting more than eight hours a day had the highest risk of dying from any cause (HR, 5.38) and from cancer, specifically (HR, 4.71).
"The findings of the present study showed that the negative effect of sitting too long appeared to be offset by meeting the Physical Activity Guidelines for Americans (150 minutes/week moderate-to-vigorous intensity leisure-time physical activity)," Cao and Dr. Yang said. "The critical issue here is that nearly three out of four U.S. cancer survivors did not meet the Physical Activity Guidelines. These data mean that guidelines and interventions need to not only promote physical activity but also include a focus on sedentary-time reduction due to different behavior-change techniques that may be required."
The new study "highlights the importance of incorporating behavioral interventions aimed at both increasing leisure-time physical activity and reducing daily sitting time into comprehensive cancer-survivorship care," said Dr. Carissa Low, an assistant professor of hematology/oncology, psychology and biomedical informatics at the University of Pittsburgh and the UPMC Hillman Cancer Center.
It, "provides strong evidence that sitting for eight or more hours per day is associated with increased risk of mortality among cancer survivor, particularly survivors who do not engage in moderate or vigorous physical exercise," Dr. Low told Reuters Health by email.
The study points to the need to "find the right interventions to modify behavior in cancer patients to promote a healthier lifestyle and decrease the chance of the cancer recurring," said Dr. Ashwani Rajput, a professor of surgery and director of the Johns Hopkins Kimmel Cancer Center-National Capital Region, in Baltimore, Maryland.
But the focus on a healthy lifestyle should start much earlier in life, Dr. Rajput said. "We need to teach kids to make the right choices - to be active and to maintain a healthy diet," he added. "If you can prevent obesity-related cancers you don't have to worry about a recurrence."
Neither Dr. Rajput nor Dr. Low was involved in the study.
SOURCE: https://bit.ly/3GbTXBo JAMA Oncology, online January 6, 2022.
By Linda Carroll
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