Obesity and colorectal cancer risk: A meta-analysis of cohort studies

Table 1 Characteristics of cohort studies investigating the association between obesity and colorectal cancer

Author, publicationyr, country, cohort	Study period	Age range	Sex	Cases/Cohort size	Body size measurement	Data collection	Cancer sites
Moore (2004)[6] USA	1948-1999	30-79	M/F	306/7566	BMI, WC	Measured	CC
Rapp (2005)[7] Austria	1985-2001	18-93	M/F	802/145 000	BMI	Measured	CC/RC
Larsson (2006)[8] Sweden	Began in 1997, Mean follow-up 7.1 yr	45-79	M	496/45 906	BMI, WC	Self-report	CC/RC
Lukanova (2006)[9] Sweden	1985-2003	30-60	M/F	244/68 786	BMI	Self-report	CC/RC
Pischon (2006)[10]	1992-2000	25-70	M/F	1570/368 277	BMI, WC, WHR	Measured	CC/RC
10 European countries
Maclnnis (2006)[11] Australia	Mean follow-up 10.4 yr	27-75	F	212/24 072	BMI, WC, WHR	Measured	CC
Ford (1999)[12] USA	1975-1992	25-74	M/F	222/13 420	BMI	Measured	CC
Giovannucci (1995)[13] USA	1986-1992	40-75	M	203/47 723	BMI, WC, WHR	Self-report	CC
Chyou (1996)[14] Japan	1965-1995	Born in 1900-1919	M	453/7945	BMI	Measured	CC/RC
Martinez (1997)[15] USA	1980-1992	30-55	F	396/89 448	BMI, WC, WHR	Self-report	CC
Bostick (1994)[16] USA	1986-1990	55-69	F	212/35 215	BMI, WHR	Self-report	CC
Terry (2002)[17] Canada	1982-1993	40-59	F	527/89 835	BMI	Self-report	CC/RC
MacInnis (2004)[18] Australia	1994-2002	27-75 99.3% 40-69	M	153/16 556	BMI, WC, WHR	Measured	CC
Terry (2001)[19] Sweden	1990-1998	40-76	F	460/61 463	BMI	Self-report	CC/RC
Lin (2004)[20] USA	average of 8.7 yr follow-up	≥ 45	F	202/37 671	BMI	Self-report	CC RC

M: male; F: female; BMI: body mass index; WC: waist circumference; WHR: waist-to-hip ratio; CC: colon cancer; RC: rectal cancer.

Table 2 Types of quantile and cut-off points for upper and lower quantiles for waist and waist-to-hip ratio (WHR) used in the studies

Study	Type of quantilesused	Waist (cm)		WHR
		Upper limit oflower quantile	Lower limit ofupper quantile	Upper limit oflower quantile	Lower limit ofupper quantile
Moore (2004)[6]	Quartiles	83.8 (M)/81.3 (F)	101.6 (M)/99.1 (F)	ND	ND
Pischon (2006)[10]	Quintiles	86 (M)/70.2 (F)	103 (M)/89 (F)	0.887 (M)/0.734 (F)	0.990 (M)/0.846 (F)
Maclnnis (2006)[11]	Tertiles	80 (F)	88 (F)	0.75 (F)	0.80 (F)
Giovannucci (1995)[13]	Quintiles	35in (M)	43 in (M)	0.90 (M)	0.99 (M)
Martinez (1997)[15]	Quintiles	27.5in (F)	34in (F)	0.728 (F)	0.833 (F)
Bostick (1994)[16]	Quintiles	ND	ND	0.764 (F)	0.906 (F)
MacInnis (2004)[18]	Quartiles	87 (M)	99.3 (M)	0.88 (M)	0.96 (M)

M: male; F: female; ND: no data.

Table 3 Comparison of the highest-to-lowest quantiles of BMI, WC and WHR to predict colorectal cancer risk

Body size measurement	Category	Pooled effect estimate (95% CI)	Pheterogeneity	Number of studies
BMI	Male (colon cancer)	1.59 (1.35-1.86)	0.82	10
	Female (colon cancer)	1.22 (1.08-1.39)	0.15	12
	Male (rectal cancer)	1.16 (0.93-1.46)	0.03	5
	Female (rectal cancer)	1.23 (0.98-1.54)	0.93	6
Waist circumference	Male (colon cancer)	1.68 (1.36-2.08)	0.31	6
	Female (colon cancer)	1.48 (1.19-1.84)	0.79	4
	Male (rectal cancer)	1.26 (0.90-1.77)	0.95	2
	Female (rectal cancer)	1.23 (0.81-1.86)	-	1
Waist-to-hip ratio	Male (colon cancer)	1.91 (1.46-2.49)	0.23	3
	Female (colon cancer)	1.49 (1.23-1.81)	0.76	4
	Male (rectal cancer)	1.93 (1.19-3.13)	-	1
	Female (rectal cancer)	1.20 (0.81-1.78)	-	1