Body mass index and lung cancer risk.

The relation of body mass index, based on self-reported weight 5 years prior to diagnosis, to lung cancer was investigated in 3,607 lung cancer cases and 9,681 controls interviewed in a hospital-based case-control study in eight US cities between 1981 and 1990. Separate analyses were carried out by smoking status and by sex. After adjustment for covariates, odds ratios for lung cancer by levels of body mass index, taking greater than or equal to 28 as the referent, showed an increasing linear trend with decreasing body mass index for current smokers and ex-smokers of both sexes and for female never smokers. These results are consistent with findings of a number of prospective studies. Further studies are needed to determine whether the association of low body mass and lung cancer is due to factors associated with leanness or to a biologic effect of leanness itself.     

Body mass index and risk of colorectal carcinoma subtypes classified by tumor differentiation status

Previous studies suggest that abnormal energy balance status may dysregulate intestinal epithelial homeostasis and promote colorectal carcinogenesis, yet little is known about how host energy balance and obesity influence enterocyte differentiation during carcinogenesis. We hypothesized that the association between high body mass index (BMI) and colorectal carcinoma incidence might differ according to tumor histopathologic differentiation status. Using databases of the Nurses’ Health Study and Health Professionals Follow-up Study, and duplication-method Cox proportional hazards models, we prospectively examined an association between BMI and the incidence of colorectal carcinoma subtypes classified by differentiation features. 120,813 participants were followed for 26 or 32 years and 1528 rectal and colon cancer cases with available tumor pathological data were documented. The association between BMI and colorectal cancer risk significantly differed depending on the presence or absence of poorly-differentiated foci (P_{heterogeneity} = 0.006). Higher BMI was associated with a higher risk of colorectal carcinoma without poorly-differentiated foci (≥30.0 vs. 18.5–22.4 kg/m²: multivariable-adjusted hazard ratio, 1.87; 95% confidence interval, 1.49–2.34; P_trend < 0.001), but not with risk of carcinoma with poorly-differentiated foci (P_trend = 0.56). This differential association appeared to be consistent in strata of tumor microsatellite instability or FASN expression status, although the statistical power was limited. The association between BMI and colorectal carcinoma risk did not significantly differ by overall tumor differentiation, mucinous differentiation, or signet ring cell component (P_{heterogeneity} > 0.03, with the adjusted α of 0.01). High BMI was associated with risk of colorectal cancer subtype containing no poorly-differentiated focus. Our findings suggest that carcinogenic influence of excess energy balance might be stronger for tumors that retain better intestinal differentiation throughout the tumor areas.     

Body mass index and lung cancer risk in women

BACKGROUND: Studies have suggested that leanness in adulthood may be a risk factor for lung cancer; however, there is justifiable concern that the observed association may be due to residual confounding by smoking, preclinical weight loss, competing causes of death, or some combination of these. METHODS: To examine this association we used data from the Canadian National Breast Screening Study, which included 89,835 women ages 40-59 years at recruitment between 1980 and 1985. During a mean of 16 years of follow-up, we observed 750 incident lung cancer cases. We used Cox proportional hazards models to estimate hazard ratios and 95% confidence intervals for the association between body mass index (BMI) and lung cancer. RESULTS: After adjustment for pack-years of smoking and other covariates, there was some evidence for inverse associations in current smokers (hazard ratio for highest BMI quintile relative to the lowest = 0.63; 95% confidence interval = 0.48-0.83) and in former smokers (0.69; 0.39-1.23), whereas in never-smokers, BMI was positively associated with lung cancer (2.19; 1.00-4.80). The results for current and former smokers were not altered by exclusion of cases diagnosed within the first 5 years of follow-up; however, in never-smokers the strength of the association was reduced. CONCLUSIONS: The present study contributes to the aggregate evidence suggesting that there may be an inverse association between BMI and lung cancer among smokers. However, the contrasting pattern of associations between BMI and lung cancer seen in ever-smokers and never-smokers in this study requires explanation.     

Body mass index and breast cancer risk in African American women

PURPOSE: Studies of the relationship between body mass index (BMI) and breast cancer in African American women have been few. We conducted a case-control study to examine whether BMI is associated with risk of breast cancer in this population. METHODS: Cases were 304 women diagnosed with breast cancer at the ages of 20 to 64 years. Controls were 305 women without a history of breast cancer. Telephone interviews were conducted to collect data on history of exposure to various factors at or before the date of diagnosis in cases or equivalent date in controls (reference date). Using logistic regression, we compared cases and controls in BMI at age 18, BMI at the reference date, and change in BMI between the two dates. RESULTS: Using BMI at reference date, we found an odds ratio (OR) of 1.75 (95% confidence interval [CI], 1.02-3.02) and 2.32 (95% CI, 1.33-4.03) for women with BMI of 25 to 29.9 and 30 or higher, respectively, compared with women having BMI lower than 25. The corresponding OR estimates for BMI at age 18 were not significantly different from the unity. The average annual change in BMI between age 18 and date of diagnosis or reference date was associated with breast cancer risk, as shown that more BMI change tended to increase breast cancer risk compared with the baseline quartile of change. When data were analyzed by menopausal status, the association was found for both post-menopausal and pre-menopausal tumors for BMI at reference date but not for BMI at age 18. There was a higher risk for more annual BMI change compared with the baseline for both pre-menopausal and post-menopausal women. CONCLUSION: Our results suggest that BMI at reference date and change in BMI were associated with increased risk of breast cancer in African American women, and the association might be found for both post-menopausal and pre-menopausal tumors.     

Prognostic significance of body mass index in Asian patients with localized renal cell carcinoma

We investigated the prognostic value of BMI (body mass index) in Asian patients with RCC (renal cell carcinoma). We evaluated 170 Asian patients who underwent surgery for localized RCC (pathologic T1-4 tumors in the absence of nodal or distant metastases) between 1996 and 2004 at our institution. Patients were stratified by BMI: 22 or less vs. greater than 22. Overall, CSS (cancer-specific survival) and RFS (recurrence-free survival) was estimated using the Kaplan-Meier method. Multivariate analysis was performed with the Cox regression model. The mean age and BMI of all patients was 62.4 ± 11.4 yr and 23.1 ± 3.2 kg/m(2), respectively. Patients' population consisted of 114 (67.1%) men and 56 (32.9%) women. The median follow-up was 50 mo. The BMI was less than 22 in 83 (49%) patients and greater than 22 in 87 (51%). There was a trend toward worse Eastern Cooperative Oncology Group (ECOG) performance status, less likely to have an incidentaloma, higher pathological stage, and more frequent microvascular invasion with lower BMI. Only the correlations between BMI and ECOG performance status (P = 0.003) and pathological stage (P = 0.015) were statistically significant. Of other relevant factors including gender, mode of presentation, ECOG performance status, C-reactive protein, histological type, Fuhrman nuclear grade, microvascular invasion, pathological stage, and adjuvant cytokine therapy, smaller BMI remained an independent predictor for worse CSS (44.5 mo vs. 56.0 mo, P = 0.041, HR = 10.99) and RFS (43.0 mo vs. 55.0 mo, P = 0.03, HR = 2.653), but not for OS (overall survival) (46.0 mo vs. 55.5 mo, P = 0.13, HR = 2.217) on multivariate analysis. Our findings identify increasing BMI in the Asian population as an independent predictor for favorable CSS and RFS in patients with RCC treated by surgery. Further studies, including a multiinstitutional, prospective Asian cohort, are required to confirm these findings.     

Body mass index and risk of diabetes mellitus in the Asia-Pacific region

Few prospective data from the Asia Pacific region are available relating body mass index to the risk of diabetes. Our objective was to provide reliable age, sex and region specific estimates of the associations between body mass index and diabetes. Twenty-seven cohort studies from Asia, New Zealand and Australia, including 154,989 participants, contributed 1,244,793 person-years of follow-up. Outcome data included a combination of incidence of diabetes (based on blood glucose measurements) and fatal diabetes events. Hazard ratios were calculated from Cox models, stratified by sex and cohort, and adjusted for age at risk and smoking. During follow-up (mean = 8 years), 75 fatal diabetes events and 242 new cases of diabetes were documented. There were continuous positive associations between baseline body mass index and risk of diabetes with each 2 kg/m2 lower body mass index associated with a 27% (23-30%) lower risk of diabetes. The associations were stronger in younger age groups, and regional comparisons demonstrated slightly stronger associations in Asian than in Australasian cohorts (P = 0.04). This overview provides evidence of a strong continuous association between body mass index and diabetes in the Asia Pacific region. The results indicate considerable potential for reduction in incidence of diabetes with population-wide lowering of body mass index in this region.     

Body mass index and cardiovascular risk factors in a rural Chinese population

The metabolic consequences of obesity are well-documented in Western populations. However, limited data are available on the association between body mass index (BMI) and cardiovascular risk factors in developing countries. The authors therefore examined the association between BMI and cardiovascular risk factors in a very lean population in China. A total of 2,542 subjects aged 20-70 years from a rural area of Anqing, China, participated in a cross-sectional survey, and 1,610 provided blood samples in 1993. Mean BMI (kg/m2) was 20.7 for men and 20.9 for women. After adjustment for age, sex, education level, occupation, current alcohol use, and cigarette smoking, BMI was significantly associated with systolic and diastolic blood pressures (p < 0.0001). The adjusted odds ratio for hypertension (systolic pressure > or =140 mmHg or diastolic pressure > or = 90 mmHg) across quintiles of BMI (quintile medians: 18.0, 19.4, 20.6, 21.8, and 24.0) were 1.0, 1.34, 2.46, 2.61, and 4.90 (95% confidence interval: 3.20, 7.50). A higher BMI was directly associated with higher levels of serum total cholesterol, triglycerides, and fasting glucose and lower levels of high density lipoprotein cholesterol. These data from a very lean Chinese population confirm independent relations between body mass and cardiovascular risk factors observed in predominantly overweight Western populations and extend the range of associations to lower BMI levels than do previous studies.     

Body mass index and occupational attainment

In this paper I investigate the impact of body mass index (BMI) on occupational attainment in England. Using pooled cross-sectional health survey data for 1997 and 1998 I find using OLS that, conditional on a comprehensive set of individual and area covariates, BMI has a positive and significant effect on occupational attainment in males and a negative and significant effect in females. Subsequent analyses with different covariates show considerable variation in the results for males, while for females the effect of BMI is significant and negative irrespective of the covariates used. IV coefficients on the BMI measures are insignificant in all models, though I am unable to identify any endogeneity problems with respect to BMI.     

Body mass index and risk of Parkinson's disease: a prospective cohort study

High body mass index has been associated with increased risk of several chronic diseases, including cardiovascular disease, and, recently, Alzheimer's disease. There are few data on the association of body mass index with Parkinson's disease, and results have been inconsistent. The authors conducted a prospective study among 10,812 men in the Harvard Alumni Health Study, followed from 1988 to 1998 (mean age at baseline: 67.7 years), to test the hypothesis that body mass index is associated with Parkinson's disease risk. Among 106 incident cases of Parkinson's disease, body mass index at baseline was not associated with Parkinson's disease risk (for body mass index <22.5, 22.5-<24.9, and > or =25.0 kg/m2: multivariate relative risks = 1.51 (95% confidence interval: 0.95, 2.40), 1.00 (referent), and 0.86 (95% confidence interval: 0.53, 1.41)). The authors had information on body mass index during late adolescence, when men entered college; this was unrelated to Parkinson's disease risk as well. Subjects who lost at least 0.5 units of body mass index per decade between college entry and 1988 had a significantly increased Parkinson's disease risk, compared with men having stable body mass index (multivariate relative risk = 2.60, 95% confidence interval: 1.10, 6.10). The authors conclude that body mass index is unrelated to Parkinson's disease risk and speculate that the observation of increased risk with body mass index loss since late adolescence may reflect weight loss due to Parkinson's disease that preceded clinical diagnosis.     

Occupational hydrocarbon exposure and risk of renal cell carcinoma

A population-based case-control study (210 cases and 210 age- sex- and frequency-matched population controls) was conducted to evaluate the association between occupational hydrocarbon exposure and risk of renal cell carcinoma. Retrospective estimates of lifetime occupational hydrocarbon exposure were made without regard to case or control status, and an exposure index was calculated based on time and score combinations. A weak positive association was found for hydrocarbon exposure in males only (odds ratio = 1.6). For those under the age of 60, exposure to moderate levels of hydrocarbons produced the highest risk, while for those over the age of 70 a dose-response relationship was found. Those overweight were at high risk for renal cell carcinoma, and there was positive interaction between hydrocarbon exposure and overweight. Alcohol use alone or in the presence of hydrocarbon exposure decreased the risk significantly.     

Relation of height and body mass index to renal cell carcinoma in two million Norwegian men and women

A positive association between body mass index (BMI) and renal cell carcinoma (RCC) has been observed. The association between height and RCC has been less clear. The authors explored these relations in a very large Norwegian cohort. Height and weight were measured in two million Norwegian men and women aged 20-74 years during 1963-2001. During follow-up, 6,453 cases of RCC were registered in the national cancer database. Measurements were also performed in 227,000 adolescents aged 14-19 years, and 154 cases of RCC were registered. Relative risks for RCC were estimated using Cox proportional hazards regression. The risk of RCC increased with increasing BMI among both adults and adolescents. Among adults, the relative risk associated with a one-unit increase in BMI was 1.05 (95% confidence interval (CI): 1.04, 1.06) in both sexes. The relative risk associated with a 10-cm increase in height was 1.19 (95% CI: 1.13, 1.26) in men and 1.17 (95% CI: 1.09, 1.26) in women. In a subgroup analysis, the relation between BMI and RCC was most pronounced in men and women who were never smokers, and the relation between height and RCC was confined to ever smokers. The authors conclude that elevated BMIs are associated with RCC risk in both males and females across a wide age range.     

Body mass index cut-points to identify cardiometabolic risk in black South Africans

Purpose

To determine optimal body mass index (BMI) cut-points for the identification of cardiometabolic risk in black South African adults.

Methods

We performed a cross-sectional study of a weighted sample of healthy black South Africans aged 25–65 years (721 men, 1386 women) from the North West and Free State Provinces. Demographic, lifestyle and anthropometric measures were taken, and blood pressure, fasting serum triglycerides, high-density lipoprotein (HDL) cholesterol and blood glucose were measured. We defined elevated cardiometabolic risk as having three or more risk factors according to international metabolic syndrome criteria. Receiver operating characteristic curves were applied to identify an optimal BMI cut-point for men and women.

Results

BMI had good diagnostic performance to identify clustering of three or more risk factors, as well as individual risk factors: low HDL-cholesterol, elevated fasting glucose and triglycerides, with areas under the curve >.6, but not for high blood pressure. Optimal BMI cut-points averaged 22 kg/m² for men and 28 kg/m² for women, respectively, with better sensitivity in men (44.0–71.9 %), and in women (60.6–69.8 %), compared to a BMI of 30 kg/m² (17–19.1, 53–61.4 %, respectively). Men and women with a BMI >22 and >28 kg/m², respectively, had significantly increased probability of elevated cardiometabolic risk after adjustment for age, alcohol use and smoking.

Conclusion

In black South African men, a BMI cut-point of 22 kg/m² identifies those at cardiometabolic risk, whereas a BMI of 30 kg/m² underestimates risk. In women, a cut-point of 28 kg/m², approaching the WHO obesity cut-point, identifies those at risk.

     

Body mass index measurement in schools

BACKGROUND: School-based body mass index (BMI) measurement has attracted much attention across the nation from researchers, school officials, legislators, and the media as a potential approach to address obesity among youth. METHODS: An expert panel, convened by the Centers for Disease Control and Prevention (CDC) in 2005, reviewed and provided expertise on an earlier version of this article. The panel comprised experts in public health, education, school counseling, school medical care, and a parent organization. This article describes the purposes of BMI measurement programs, examines current practices, reviews existing research, summarizes the recommendations of experts, identifies concerns, and provides guidance including a list of safeguards and ideas for future research. RESULTS: The implementation of school-based BMI measurement for surveillance purposes, that is, to identify the percentage of students in a population who are at risk for weight-related problems, is widely accepted; however, considerable controversy exists over BMI measurement for screening purposes, that is, to assess the weight status of individual students and provide this information to parents with guidance for action. Although some promising results have been reported, more evaluation is needed to determine whether BMI screening programs are a promising practice for addressing obesity. CONCLUSIONS: Based on the available information, BMI screening meets some but not all of the criteria established by the American Academy of Pediatrics for determining whether screening for specific health conditions should be implemented in schools. Schools that initiate BMI measurement programs should evaluate the effects of the program on BMI results and on weight-related knowledge, attitudes, and behaviors of youth and their families; they also should adhere to safeguards to reduce the risk of harming students, have in place a safe and supportive environment for students of all body sizes, and implement science-based strategies to promote physical activity and healthy eating.     

Body mass index and risk of infections: a Mendelian randomization study of 101,447 individuals

Body mass index (BMI) has been related to risk of infections. The aim of this study was to assess the shape of the association between BMI and risk of infections and to evaluate whether such associations represent causality. We included 101,447 individuals from The Copenhagen General Population Study who had BMI measured. Outcome was hospital contacts related to infections. The shape of the association between BMI and risk of infections was examined using restricted cubic spline Cox regression. To evaluate causality, we used Mendelian randomization, an epidemiological method that counteracts confounding and reverse causality by using genetic variation as instrumental variables. We created a genetic risk score based on five genetic variants causing lifelong higher BMI and used this score in instrumental variable analysis. During median follow-up of 8.8 years, 10,263 hospital contacts related to infections were recorded. We found a U-shaped association between BMI and risk of any infection and pneumonia, and a linear association between BMI and risk of skin infection, urinary tract infection, and sepsis. In instrumental variable analyses, higher BMI was associated with increased risk of skin infection: odds ratio 1.12 (95% CI 1.03–1.22) for a genetically induced 1 unit increase in BMI. Observationally, low as well as high BMI was associated with increased risk of any infection and pneumonia, whereas only high BMI was associated with increased risk of skin infection, urinary tract infection, and sepsis. High BMI was causally associated with increased risk of skin infection.