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Table 2 Overall and stratified meta-analyses of relative risk estimates (associations) for physical activity and risk of colorectal cancer by BMI subgroups

From: Effects of physical activity on colorectal cancer risk among family history and body mass index subgroups: a systematic review and meta-analysis

Overall/stratified analysis

Total number of estimates

Number of casesa

Pooled RR (95% CI)

I2 (%)

Pheterogeneity

P across subgroups

P across high and low BMI

Low BMI

 Overall

27

7045

0.74(0.66–0.83)

47.9

0.003

  

Sex

 Male

12

2590

0.76 (0.64–0.92)

53.1

0.015

0.551

 

 Female

8

1639

0.72 (0.57–0.91)

33.6

0.160

  

 Both

7

2816

0.70 (0.56–0.89)

50.2

0.061

  

Study Design

 Cohort

11

3073

0.76 (0.61–0.94)

59.3

0.006

0.088

 

 Case-control

16

3972

0.72 (0.62–0.84)

40.7

0.046

  

Cancer Site

 Colon

17

3436

0.69 (0.59–0.81)

41.5

0.038

0.410

 

 Colorectal

6

2854

0.74 (0.56–0.98)

55.6

0.047

  

 Rectal

4

755

0.94 (0.83–1.06)

0.0

0.942

  

Interactionb

 No

13

3128

0.78 (0.66–0.92)

37.3

0.004

0.462

 

 Yes

14

3917

0.70 (0.59–0.84)

57.6

0.085

  

Physical Activity Type

 Total

9

2681

0.74 (0.61–0.89)

32.7

0.156

0.605

 

 Recreational

12

3874

0.78 (0.64–0.94)

60.5

0.003

  

 Commuting

6

490

0.64 (0.51–0.79)

0.0

0.675

  

Physical Activity Measurement

 Adulthood/lifetimec

16

5151

0.72 (0.64–0.82)

16.0

0.271

0.497

 

 Past year or two

6

1319

0.75 (0.56–1.01)

67.8

0.008

  

 Regulard

5

575

0.77 (0.51–1.17)

63.8

0.026

  

Physical Activity Assessment

 MET-h/day or week

13

2188

0.73 (0.62–0.87)

52.4

0.014

0.969

 

 Kcal/week

2

1993

0.75 (0.54–1.04)

0.0

0.437

  

 Times/week or month

3

1939

0.75 (0.53–1.05)

78.1

0.010

  

 Othere

9

925

0.72 (0.54–0.98)

41.6

0.090

  

Physical Activity Reference Group

 No activity

9

4453

0.70 (0.57–0.85)

41.9

0.088

0.538

 

 Some activity

18

2592

0.76 (0.65–0.88)

47.8

0.013

  

Geographical Region

 North America

12

5026

0.82 (0.71–0.94)

47.7

0.033

0.122

 

 Europe

5

920

0.60 (0.38–0.93)

59.2

0.044

  

 Asia

8

824

0.66 (0.55–0.80)

7.4

0.373

  

 Australia

2

275

0.71 (0.38–1.30)

0.0

0.482

  

High BMI

 Overall

36

9407

0.65 (0.53–0.79)

89.0

<0.001

 

0.389

Sex

 Male

17

2928

0.56 (0.34–0.94)

74.9

<0.001

0.268

0.264

 Female

9

1568

0.61 (0.47–0.79)

92.1

<0.001

 

0.333

 Both

10

4911

0.83 (0.65–1.05)

82.8

<0.001

 

0.384

Study Design

 Cohort

15

4625

0.93 (0.78–1.13)

64.1

<0.001

0.002

0.178

 Case-control

21

4782

0.51 (0.39–0.66)

88.0

<0.001

 

0.053

Cancer Site

 Colon

20

5330

0.58 (0.44–0.79)

91.5

<0.001

0.282

0.435

 Colorectal

9

2841

0.74 (0.49–1.11)

85.9

<0.001

 

0.948

 Rectal

7

1236

0.74 (0.62–0.88)

4.1

0.395

 

0.052

Interactionb

 No

18

4881

0.87 (0.79–0.96)

0.0

0.761

0.001

0.220

 Yes

18

4526

0.48 (0.34–0.68)

93.4

<0.001

 

0.081

Physical Activity Type

 Total

13

4141

0.81 (0.68–0.96)

40.4

0.065

<0.001

0.424

 Recreational

19

4830

0.74 (0.61–0.91)

75.3

<0.001

 

0.810

 Commuting

4

436

0.21 (0.14–0.32)

81.9

0.001

 

0.001

Physical Activity Measurement

 Adulthood/lifetimec

20

7082

0.54 (0.40–0.73)

93.5

<0.001

0.022

0.179

 Past year or two

10

1985

0.75 (0.64–0.87)

3.5

0.408

 

0.780

 Regulard

6

340

1.00 (0.73–1.38)

21.7

0.270

 

0.366

Physical Activity Assessment

 MET-h/day or week

13

2411

0.55 (0.37–0.81)

90.8

<0.001

0.086

0.224

 Kcal/week

5

2058

0.57 (0.45–0.72)

20.3

0.285

 

0.251

 Times/week or month

5

3549

0.90 (0.67–1.19)

87.9

<0.001

 

0.478

 Othere

13

1389

0.77 (0.59–1.00)

49.8

0.030

 

0.778

Physical Activity Reference Group

 No activity

14

8521

0.77 (0.67–0.87)

41.2

<0.001

0.132

0.474

 Some activity

22

4745

0.57 (0.40–0.82)

92.4

0.054

 

0.199

Geographical Region

 North America

21

6990

0.75 (0.64–0.87)

69.6

<0.001

0.127

0.525

 Europe

7

1239

0.67 (0.45–0.99)

69.9

0.003

 

0.724

 Asia

6

583

0.36 (0.19–0.66)

92.0

<0.001

 

0.090

 Australia

2

595

0.98 (0.57–1.68)

45.1

0.177

 

0.520

  1. Abbreviations: BMI body mass index, MET metabolic equivalent of task
  2. aBMI subgroup-specific case numbers were not described for Gerhardsson (1990) [30] Slattery (1997) [36], thus total cases were used for case numbers from these two studies
  3. bEstimates representing an interaction between physical activity and BMI on colorectal cancer risk
  4. cStudies with over 10 years of physical activity measurement were included in this category
  5. dTime period of measurement not specified
  6. eOther measures include a study’s own physical activity index or unique classification of active vs. inactive individuals
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BMC Cancer

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