Sitting down for more than 30 minutes every day may increase the risk of dying from cancer, a study has found.
Researchers at the University of Glasgow found sitting or reclining for more than half-an-hour at a time every day was linked with a higher risk of cancer death, with that risk rising for each hour of continuous inactivity.
However, scientists found the risk could be slashed by more than 20% if people swap sedentary behaviour for physical activity.
The findings, from a study published in PLOS Medicine, show the negative health impacts of prolonged periods of sedentary behaviour on a daily basis.
The researchers found breaking up sedentary behaviour with periods of physical activity could help reduce a range of cancer risks.
The activities included light intensity exercises, including slow walking or everyday tasks such as housework.
Long periods of sedentary behaviour, such as sitting or lying down while awake, have been associated with an increased risk of cardiovascular disease and some cancers.
But Glasgow University suggested that, until the study, not enough was known about the importance of how sedentary behaviour is accumulated, and whether light activity would make a difference.
The research team analysed data from wearable devices worn by more than 91,000 UK Biobank participants who were followed up for an average of 12 years.
The data showed the total amount of prolonged inactivity – continuous inactivity for more than 30 minutes – was associated with cancer risks.
Each additional hour of prolonged inactivity every day was associated with a 10% higher risk of cancer death.
The researchers found the risk could be mitigated by replacing long spells of inactivity with movement.
They found the risk of cancer death was 12% lower when one hour of sedentary behaviour was replaced with light physical activity each day, including slow walking or household tasks such as ironing or dishwashing.
Cancer death risk was 8% lower when 30 minutes of inactivity was replaced with moderate physical activity each day, including walking at an average pace.
The risk was 22% lower when five minutes of inactivity was replaced with five minutes of vigorous physical activity each day, the study found.
Dr Frederick Ho, lead author of the study, said: “What our data shows is that sitting for more than 30 minutes at a time is particularly linked to a higher risk of cancer.
“The good news is that breaking up your sitting time with something as simple as a short walk could be protective.
“Current health guidelines focus heavily on moderate or vigorous exercise, but our findings show that light movement shouldn’t be ignored.
“Moving forward, clinical trials will help us move beyond blanket advice and develop personalised strategies for breaking up sitting time.”
The study, Accelerometry-measured prolonged and interrupted sedentary behaviour and cancer incidence and mortality: A cohort study of 91,292 UK Biobank participants, was published in PLOS Medicine.