Susanna C. Larsson

Diabetes mellitus and risk of breast cancer: A meta‐analysis

Diabetes mellitus has been associated with an increased risk of several types of cancers, but its relationship with breast cancer remains unclear. We conducted a meta‐analysis of case–control and cohort studies to assess the evidence regarding the association between diabetes and risk of breast cancer. Studies were identified by searching MEDLINE (1966–February 2007) and the references of retrieved articles. We identified 20 studies (5 case–control and 15 cohort studies) that reported relative risk (RR) estimates (odds ratio, rate ratio/hazard ratio, or standardized incidence ratio) with 95% confidence intervals (CIs) for the relation between diabetes (largely Type II diabetes) and breast cancer incidence. Summary RRs were calculated using a random‐effects model. Analysis of all 20 studies showed that women with (versus without) diabetes had a statistically significant 20% increased risk of breast cancer (RR, 1.20; 95% CI, 1.12–1.28). The summary estimates were similar for case–control studies (RR, 1.18; 95% CI, 1.05–1.32) and cohort studies (RR, 1.20; 95% CI, 1.11–1.30). Meta‐analysis of 5 cohort studies on diabetes and mortality from breast cancer yielded a summary RR of 1.24 (95% CI, 0.95–1.62) for women with (versus without) diabetes. Findings from this meta‐analysis indicate that diabetes is associated with an increased risk of breast cancer.

Meat consumption and risk of colorectal cancer: a meta-analysis of prospective studies.

Accumulating epidemiologic evidence indicates that high consumption of red meat and of processed meat may increase the risk of colorectal cancer. We quantitatively assessed the association between red meat and processed meat consumption and the risk of colorectal cancer in a meta‐analysis of prospective studies published through March 2006. Random‐effects models were used to pool study results and to assess dose‐response relationships. We identified 15 prospective studies on red meat (involving 7,367 cases) and 14 prospective studies on processed meat consumption (7,903 cases). The summary relative risks (RRs) of colorectal cancer for the highest vs. the lowest intake categories were 1.28 (95% confidence interval (CI) = 1.15–1.42) for red meat and 1.20 (95% CI = 1.11–1.31) for processed meat. The estimated summary RRs were 1.28 (95% CI = 1.18–1.39) for an increase of 120 g/day of red meat and 1.09 (95% CI = 1.05–1.13) for an increase of 30 g/day of processed meat. Consumption of red meat and processed meat was positively associated with risk of both colon and rectal cancer, although the association with red meat appeared to be stronger for rectal cancer. In 3 studies that reported results for subsites in the colon, high consumption of processed meat was associated with an increased risk of distal colon cancer but not of proximal colon cancer. The results of this meta‐analysis of prospective studies support the hypothesis that high consumption of red meat and of processed meat is associated with an increased risk of colorectal cancer.

Overweight, obesity and risk of liver cancer: a meta-analysis of cohort studies

Cohort studies of excess body weight and risk of liver cancer were identified for a meta-analysis by searching MEDLINE and EMBASE databases from 1966 to June 2007 and the reference lists of retrieved articles. Results from individual studies were combined using a random-effects model. We identified 11 cohort studies, of which seven on overweight (with a total of 5037 cases) and 10 on obesity (with 6042 cases) were suitable for meta-analysis. Compared with persons of normal weight, the summary relative risks of liver cancer were 1.17 (95% confidence interval (CI): 1.02–1.34) for those who were overweight and 1.89 (95% CI: 1.51–2.36) for those who were obese. This meta-analysis finds that excess body weight is associated with an increased risk of liver cancer.

Diabetes mellitus and risk of bladder cancer: a meta-analysis

Aims/hypothesisEpidemiological evidence indicates that individuals with diabetes mellitus have an increased risk of several cancers. We performed a systematic review with meta-analysis to evaluate the association between diabetes and risk of bladder cancer.MethodsPertinent studies were identified by searching MEDLINE (from January 1966 to July 2006) and by reviewing the reference lists of retrieved articles. We included case–control and cohort studies reporting relative risk (RR) estimates with 95% CIs (or data to calculate them) of bladder cancer associated with diabetes. Studies of type 1 diabetes were not included. Summary RRs were calculated using a random-effects model.ResultsA total of 16 studies (seven case–control studies, three cohort studies and six cohort studies of diabetic patients) fulfilled the inclusion criteria. Analysis of all studies showed that diabetes was associated with an increased risk of bladder cancer, compared with no diabetes (RR = 1.24, 95% CI 1.08–1.42). There was strong evidence of heterogeneity among these studies (p < 0.0001). Stratification by study design found that diabetes was associated with an increased risk of bladder cancer in case–control studies (RR = 1.37, 95% CI 1.04–1.80, pheterogeneity = 0.005) and cohort studies (RR = 1.43, 95% CI 1.18–1.74, pheterogeneity = 0.17), but not in cohort studies of diabetic patients (RR = 1.01, 95% CI 0.91–1.12, pheterogeneity = 0.35).Conclusions/interpretationFindings from this meta-analysis suggest that individuals with diabetes may have a modestly increased risk of bladder cancer.

Body mass index and pancreatic cancer risk: A meta-analysis of prospective studies.

A number of studies have examined the association between body mass index (BMI) and risk of pancreatic cancer, but uncertainty about the relationship remains. We performed a meta‐analysis to summarize the evidence from prospective studies investigating this association. We searched MEDLINE for studies published in any language from 1966 to November 2006. Prospective studies were included if they reported relative risks (RRs) with 95% confidence intervals (CIs) for the association between BMI and pancreatic cancer incidence or mortality. Study‐specific RR estimates were combined by use of a random‐effects model. A total of 21 independent prospective studies, involving 3,495,981 individuals and 8,062 pancreatic cancer cases, met the inclusion criteria. The estimated summary RR of pancreatic cancer per 5 kg/m2 increase in BMI was 1.12 (95% CI, 1.06–1.17; p‐heterogeneity = 0.13) in men and women combined, 1.16 (95% CI, 1.05–1.28; p‐heterogeneity = 0.001) in men, and 1.10 (95% CI, 1.02–1.19; p‐heterogeneity = 0.12) in women. There was no evidence of publication bias (p = 0.58). Findings from this meta‐analysis of prospective studies support a positive association between BMI and risk of pancreatic cancer in men and women.

Red meat consumption and risk of cancers of the proximal colon, distal colon and rectum : the Swedish Mammography Cohort

Although there is considerable evidence that high consumption of red meat may increase the risk of colorectal cancer, data by subsite within the colon are sparse. The objective of our study was to prospectively examine whether the association of red meat consumption with cancer risk varies by subsite within the large bowel. We analyzed data from the Swedish Mammography Cohort of 61,433 women aged 40–75 years and free from diagnosed cancer at baseline in 1987–1990. Diet was assessed at baseline using a self‐administered food‐frequency questionnaire. Over a mean follow‐up of 13.9 years, we identified 234 proximal colon cancers, 155 distal colon cancers and 230 rectal cancers. We observed a significant positive association between red meat consumption and risk of distal colon cancer (p for trend = 0.001) but not of cancers of the proximal colon (p for trend = 0.95) or rectum (p for trend = 0.32). The multivariate rate ratio for women who consumed 94 or more g/day of red meat compared to those who consumed less than 50 g/day was 2.22 (95% confidence interval [CI] 1.34–3.68) for distal colon, 1.03 (95% CI 0.67–1.60) for proximal colon and 1.28 (95% CI 0.83–1.98) for rectum. Although there was no association between consumption of fish and risk of cancer at any subsite, poultry consumption was weakly inversely related to risk of total colorectal cancer (p for trend = 0.04). These findings suggest that high consumption of red meat may substantially increase the risk of distal colon cancer. Future investigations on red meat and colorectal cancer risk should consider cancer subsites separately.

Blood 25-hydroxyvitamin D concentration and hypertension: a meta-analysis.

Objectives Increasing evidence indicates that vitamin D may influence the risk of hypertension, which is a major risk factor for cardiovascular disease. We conducted a meta-analysis to quantitatively review and summarize the results on the association between blood 25-hydroxyvitamin D concentrations and hypertension. Methods Relevant studies were identified by a search of PubMed and EMBASE databases until November 2010. We also reviewed the references of retrieved articles. We included prospective and cross-sectional studies with blood 25-hydroxyvitamin D concentrations as the exposure and hypertension as the outcome. Studies had to report results as a relative risk or an odds ratio. We used random-effects model. Results Of the 18 studies included in the meta-analysis, 4 were prospective studies and 14 were cross-sectional studies. The pooled odds ratio of hypertension was 0.73 [95% confidence interval (CI) 0.63–0.84] for the highest versus the lowest category of blood 25-hydroxyvitamin D concentration. In a dose–response meta-analysis, the odds ratio for a 40 nmol/l (16 ng/ml) (approximately 2 SDs) increment in blood 25-hydroxyvitamin D concentration was 0.84 (95% CI 0.78–0.90). Conclusion Findings from this meta-analysis indicate that blood 25-hydroxyvitamin D concentration is inversely associated with hypertension.

Whole grain consumption and risk of colorectal cancer: a population-based cohort of 60 000 women

We examined prospectively the association between whole grain consumption and colorectal cancer risk in the population-based Swedish Mammography Cohort. A total of 61 433 women completed a food-frequency questionnaire at baseline (1987–1990) and, through linkage with the Swedish Cancer Registry, 805 incident cases of colorectal cancer were identified during a mean follow-up of 14.8 years. High consumption of whole grains was associated with a lower risk of colon cancer, but not of rectal cancer. The multivariate rate ratio (RR) of colon cancer for the top category of whole grain consumption (⩾4.5 servings day−1) compared with the bottom category (<1.5 servings day−1) was 0.67 (95% confidence interval (CI), 0.47–0.96; P-value for trend=0.06). The corresponding RR after excluding cases occurring within the first 2 years of follow-up was 0.65 (95% CI, 0.45–0.94; P-value for trend=0.04). Our findings suggest that high consumption of whole grains may decrease the risk of colon cancer in women.

Overall obesity, abdominal adiposity, diabetes and cigarette smoking in relation to the risk of pancreatic cancer in two Swedish population-based cohorts

We examined the associations of body mass index (BMI), waist circumference, a history of diabetes, and cigarette smoking with risk of pancreatic cancer among 37 147 women and 45 906 men followed up during 560 666 person-years in the Swedish Mammography Cohort and the Cohort of Swedish Men; 136 incident cases of pancreatic cancer were diagnosed. The multivariate rate ratio (RR) of pancreatic cancer for obese women and men (BMI ⩾30 kg/m2) was 1.81 (95% CI: 1.04–3.15) compared to those with a BMI of 20–25 kg/m2. For a difference of 20 cm (about two standard deviations) in waist circumference, the multivariate RRs were 1.32 (95% CI: 0.73–2.37) among women and 1.74 (95% CI: 1.00–3.01) among men. Pancreatic cancer risk was associated with history of diabetes (multivariate RR: 1.88; 95% CI: 1.09–3.26) and cigarette smoking (multivariate RR for current compared with never smokers: 3.06; 95% CI: 1.99–4.72). Current smokers of ⩾40 pack-years had a five-fold elevated risk compared with never smokers. Risk among past smokers approached the RR for never smokers within 5–10 years following smoking cessation. Findings from this prospective study support positive relationships of overall obesity, abdominal adiposity, diabetes and smoking with risk of pancreatic cancer.

Magnesium intake and risk of type 2 diabetes: a meta‐analysis

Objective.  To assess the association between magnesium intake and risk of type 2 diabetes.