How long a person sits matters, but so does how often they get up. A new study found that every additional hour of prolonged, uninterrupted sitting was associated with a 9% higher risk of dying from cancer. The research tracked more than 91,000 adults over more than 12 years.
The findings were published in the open access journal PLOS Medicine. The study was led by Frederick Ho of the University of Glasgow, UK, and colleagues. Researchers drew their data from the UK Biobank, a large health database that has followed hundreds of thousands of participants over many years.
Each of the 91,292 participants wore an activity monitor for seven days. Researchers then followed the group for a median of 12.38 years, tracking cancer diagnoses and deaths. The study separated sedentary time into two categories: prolonged and interrupted. Prolonged sedentary behavior meant sitting for at least 30 minutes with at least 90% of that period spent sedentary. Interrupted sedentary behavior meant shorter stretches of sitting, or periods in which more than 10% of the time involved movement.
Earlier research has linked sedentary behavior in general to poorer health outcomes. Most current public health guidance focuses on reducing total sedentary time. This study suggests the pattern of that sitting time may matter just as much as the total amount.
Sitting in long, unbroken stretches carried a higher risk than sitting the same total amount of time broken into shorter bouts. Greater amounts of prolonged sedentary behavior were associated with higher risk of overall cancer incidence, cancer mortality, obesity-related cancers, and type 2 diabetes-related cancers. Obesity-related cancers in the study included esophageal, liver, kidney, pancreatic, colorectal, breast, ovarian, and thyroid cancers. Interrupted sedentary behavior showed the opposite pattern, with lower risk across all outcomes examined.
Researchers also estimated what might happen if prolonged sitting were replaced with movement. Substituting one hour per day of prolonged sedentary behavior with light physical activity was associated with a 12% lower risk of cancer death.
