Table 2.

Summary risk estimates of high vs. low physical activity (PA), stratified by selected characteristics.

Stratification variable	Number of risk estimates included	Relative risk (95% confidence interval) for high vs. low PA	I² (%)	p
Total digestive-system cancer	161	0.82 (0.79–0.85)	57	<0.001
Cancer site
Colon cancer	33	0.81 (0.76–0.81)	41	<0.001
Rectal cancer	24	0.88 (0.80–0.98)	47
Colorectal cancer	23	0.77 (0.69–0.85)	82
Gallbladder cancer	2	0.79 (0.64–0.98)	0
Gastric cancer	17	0.83 (0.76–0.91)	33
Liver cancer	5	0.73 (0.60–0.89)	56
Oral cavity and pharynx cancer	11	0.79 (0.72–0.87)	32
Pancreas cancer	33	0.85 (0.78–0.93)	45
Esophagus cancer	13	0.84 (0.66–1.07)	62
Study design
Prospective studies	98	0.88 (0.85–0.91)	43	<0.001
Case-control studies	63	0.73 (0.68–0.78)	49
Gendera
Men	63	0.84 (0.80–0.88)	41	<0.001
Women	38	0.85 (0.78–0.93)	51
Study geographic region
Asia	52	0.75 (0.69–0.81)	67	<0.001
Europe	48	0.85 (0.81–0.90)	54
Australia	12	0.77 (0.69–0.87)	0
Middle East	2	0.20 (0.01–3.07)	80
North America	47	0.86 (0.81–0.93)	43
PA domain
Total activity	34	0.80 (0.75–0.86)	41	<0.001
Recreational activity	107	0.82 (0.79–0.86)	65
Occupational activity	20	0.85 (0.76–0.94)	0
Timing in life of PA
Recent	76	0.84 (0.80–0.88)	60	<0.001
Consistent over time	59	0.77 (0.72–0.82)	48
Past	26	0.86 (0.78–0.95)	40
Adjustment for body mass index
Adjusted	120	0.82 (0.79–0.86)	59	<0.001
Not adjusted	41	0.80 (0.74–0.87)	49
Adjustment for smoking
Adjusted	139	0.83 (0.80–0.86)	49	<0.001
Not adjusted	22	0.77 (0.69–0.87)	76
Adjustment for alcohol
Adjusted	115	0.84 (0.81–0.87)	50	<0.001
Not adjusted	46	0.77 (0.71–0.84)	63

Note: The p value for difference across strata of selected characteristics was estimated from random effects meta-regression comparing a model that included the stratification variable with the null model that did not include the stratification variable.

^aStudies that include both men and women were not considered for subgroup analysis.