Body mass index and risk of colorectal cancer in Chinese Singaporeans: the Singapore Chinese Health Study

Abstract

Background: The authors chose to examine the association between body mass index (BMI) and incident colorectal cancer across the spectrum of BMI, including underweight persons, because detailed prospective cohort data on this topic in Asians is scarce, as is data on underweight persons (BMI, <18.5 kg/m(2)) in any population.

Methods: Analysis of the Singapore Chinese Health Study included 51,251 men and women aged 45-74 years enrolled in 1993-1998 and followed through 2007. Incident cancer cases and deaths among cohort members were identified through record linkage, and 980 cases were identified. Cox regression models were used to investigate the association of baseline BMI with risk of incident colorectal cancer during a mean of 11.5 years of follow-up.

Results: A significant, U-shaped, quadratic association was observed between BMI and colon cancer risk, with increased risk in BMIs ≥27.5 and <18.5 kg/m(2). The association was more pronounced in never smokers and most prominent when further limiting the sample to those free of diabetes and cases with longer than 5 years of follow-up. Localized cases had a more pronounced association in BMIs ≥27.5, whereas advanced cases had a more pronounced association in BMIs <18.5 kg/m(2) . No association was found in relation to rectal cancer risk. The association was also stronger among patients aged 65 years and older.

Conclusions: BMI displays a U-shaped, quadratic association with colon cancer risk in this Chinese population in Southeast Asia.

Figure 1

Hazard ratios of colon cancer in never-smokers, without reported diabetes, and excluding persons with less than 5 years of follow up time (N=31,851 and 236 cases colon cancer). Model adjusted for age, sex, year of enrollment, dialect, education, familial history of cancer, alcohol intake, dietary pattern score, physical activity, sleep and energy intake. Points represent hazard ratio (HR) point estimate and error bars represent 95% confidence intervals. P value for quadratic association =0.0016. Respective case counts for colon cancer by BMI (< 18.5, 18.5–21.4, 21.5–24.4, 24.5–27.4, ≥ 27.5): Cancer (21, 65, 67, 48, 37).

Figure 2

Hazard ratios of colon cancer in never-smokers, without reported diabetes, and excluding persons with less than 5 years of follow up time stratified by staging level (local vs. advanced) of cases (Duke=A or B for local) and (Duke= C or D for advanced) (N=31,670 and 128 cases localized colon cancer, Duke=A or B).and (N=31,706 and 120 cases advanced colon cancer, Duke = C or D). Model adjusted for age, sex, year of enrollment, dialect, education, familial history of cancer, alcohol intake, dietary pattern score, physical activity, sleep, and energy intake. Points represent hazard ratio (HR) point estimate and error bars represent 95% confidence intervals. P value for quadratic association =0.003 for localized and p=0.045 for advanced.