Association between physical activity and mortality in colorectal cancer: A meta‐analysis of prospective cohort studies

Several prospective cohort studies have examined the association between prediagnosis and/or postdiagnosis physical activity (PA) on colorectal cancer outcomes and reported conflicting results. To quantitatively assess this association, we have conducted a meta‐analysis of prospective studies. Databases and reference lists of relevant studies were searched using MEDLINE and EMBASE up to January 2013. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using random‐effects models. For this meta‐analysis, a total of seven prospective cohort studies were included. The analysis included 5,299 patients for prediagnosis PA and 6,348 patients for postdiagnosis PA, followed up over a period ranging from 3.8 to 11.9 years. The analyses showed that patients who participated in any amount of PA before diagnosis had a RR of 0.75 (95% CI: 0.65–0.87, p < 0.001) for colorectal cancer‐specific mortality compared to patients who did not participate in any PA. Those who participated in high PA before diagnosis (vs. low PA) had a RR of 0.70 (95% CI: 0.56–0.87, p = 0.002). Similarly, patients who participated in any PA after diagnosis had a RR of 0.74 (95% CI: 0.58–0.95, p = 0.02) for colorectal cancer‐specific mortality compared to patients who did not participate in any PA. Those who participated in high PA after diagnosis (vs. low PA) had a RR of 0.65 (95% CI: 0.47–0.92, p = 0.01). Similar inverse associations of prediagnosis or postdiagnosis PA were found for all‐cause mortality. In conclusion, both prediagnosis and postdiagnosis PA were associated with reduced colorectal cancer‐specific mortality and all‐cause mortality.     

Meat subtypes and their association with colorectal cancer: Systematic review and meta‐analysis

Associations between specific red meat subtypes and risk of colorectal cancer (CRC) have been investigated in a number of epidemiological studies. However, no publication to date has summarised the overall epidemiological evidence. We conducted a systematic review and meta‐analysis of prospective studies (cohort, nested case‐control or case‐cohort studies), which reported relative risk (RR) estimates and 95% confidence intervals (CI) for the association between intake of meat subtypes with colorectal, colon or rectal cancer or colorectal adenoma risk. PubMed and ISI Web of Science were searched up until August 1, 2014. Nineteen studies examined meat subtypes (5 beef, 5 pork, 2 lamb, 1 veal and 19 poultry) and associations with colorectal, colon or rectal cancer risk and 4 studies examined associations with adenoma risk (1 beef and 4 poultry). Comparing highest versus lowest intake, beef consumption was associated with an increased risk of CRC (RR = 1.11, 95% CI = 1.01 to 1.22) and colon cancer (RR = 1.24, 95% CI = 1.07 to 1.44), but no association was found with rectal cancer (RR = 0.95, 95% CI = 0.78 to 1.16). Higher consumption of lamb was also associated with increased risk of CRC (RR = 1.24, 95% CI = 1.08 to 1.44). No association was observed for pork (RR = 1.07, 95% CI = 0.90 to 1.27), but some between study heterogeneity was observed. No association was observed for poultry consumption and risk of colorectal adenomas or cancer. This meta‐analysis suggests that red meat subtypes differ in their association with CRC and its sub sites. Further analysis of data from prospective cohort studies is warranted, especially regarding the role of pork.     

A meta-analysis of coffee consumption and pancreatic cancer

BackgroundSince when in 1981 a case–control study showed a positive association between coffee and pancreatic cancer, several studies reported inconsistent results on this issue.Materials and methodsWe conducted a systematic bibliography search updated March 2011 to identify observational studies providing quantitative estimates for pancreatic cancer risk in relation to coffee consumption. We used a meta-analytic approach to estimate overall relative risk (RR) and 95% confidence interval (CI) for the highest versus the lowest coffee consumption categories, using random-effects models.ResultsBased on 37 case–control and 17 cohort studies (10 594 cases), the pooled RR for the highest versus lowest intake was 1.13 (95% CI 0.99–1.29). Considering only the smoking-adjusting studies, the pooled RRs were 1.10 (95% CI 0.92–1.31) for the 22 case–control, 1.04 (95% CI 0.80–1.36) for the 15 cohort, and 1.08 (95% CI 0.94–1.25) for all studies. The pooled RR for the increment of one cup of coffee per day was 1.03 (95% CI 0.99–1.06) for the 28 smoking-adjusting studies reporting three or more coffee consumption categories. No significant heterogeneity was observed across strata of study design, sex, geographic region, and other selected characteristics.ConclusionsThis meta-analysis provides quantitative evidence that coffee consumption is not appreciably related to pancreatic cancer risk, even at high intakes.     

Coffee consumption and risk of endometrial cancer: findings from a large up-to-date meta-analysis

Several epidemiological studies have examined the association between coffee drinking and risk of endometrial cancer. To provide a quantitative assessment of this association, we conducted a meta-analysis of observational studies published up to October 2011 through a search of MEDLINE and EMBASE databases and the reference lists of retrieved article. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated using a random-effects model, and generalized least square trend estimation was used to assess dose-response relationships. A total of 16 studies (10 case-control and six cohort studies) on coffee intake with 6,628 endometrial cancer cases were included in the meta-analysis. The pooled RR of endometrial cancer for the highest versus lowest categories of coffee intake was 0.71 (95% CI: 0.62-0.81; p for heterogeneity = 0.13). By study design, the pooled RRs were 0.69 (95% CI: 0.55-0.87) for case-control studies and 0.70 (95% CI: 0.61-0.80) for cohort studies. By geographic region, the inverse association was stronger for three Japanese studies (pooled RR = 0.40; 95% CI: 0.25-0.63) than five studies from USA/Canada (pooled RR = 0.69; 95% CI: 0.60-0.79) or eight studies from Europe (pooled RR = 0.79; 95% CI: 0.63-0.99). An increment of one cup per day of coffee intake conferred a pooled RR of 0.92 (95% CI: 0.90-0.95). In conclusion, our findings suggest that increased coffee intake is associated with a reduced risk of endometrial cancer, consistently observed for cohort and case-control studies. More large studies are needed to determine subgroups to obtain more benefits from coffee drinking in relation to endometrial cancer risk.     

Dietary supplement use and colorectal cancer risk: A systematic review and meta‐analyses of prospective cohort studies

Use of dietary supplements is rising in countries where colorectal cancer is prevalent. We conducted a systematic literature review and meta‐analyses of prospective cohort studies on dietary supplement use and colorectal cancer risk. We identified relevant studies in Medline, Embase and Cochrane up to January 2013. Original and peer‐reviewed papers on dietary supplement use and colorectal cancer, colon cancer, or rectal cancer incidence were included. “Use‐no use”(U‐NU), “highest‐lowest”(H‐L) and “dose‐response”(DR) meta‐analyses were performed. Random‐effects models were used to estimate summary estimates. In total, 24 papers were included in the meta‐analyses. We observed inverse associations for colorectal cancer risk and multivitamin (U‐NU: RR = 0.92; 95% CI: 0.87,0.97) and calcium supplements (U‐NU: RR = 0.86; 95% CI: 0.79,0.95; H‐L: RR = 0.80; 95% CI: 0.70,0.92; DR: for an increase of 100 mg/day, RR = 0.96; 95% CI: 0.94,0.99). Inconsistent associations were found for colon cancer risk and supplemental vitamin A and vitamin C, and for colorectal cancer risk and supplemental vitamin D, vitamin E, garlic and folic acid. Meta‐analyses of observational studies suggest a beneficial role for multivitamins and calcium supplements on colorectal cancer risk, while the association with other supplements and colorectal cancer risk is inconsistent. Residual confounding of lifestyle factors might be present. Before recommendations can be made, an extensive assessment of dietary supplement use and a better understanding of underlying mechanisms is needed.     

Adherence to Mediterranean diet and risk of cancer: A systematic review and meta‐analysis of observational studies

The aim of this research study was to meta‐analyze the effects of adherence to Mediterranean diet (MD) on overall cancer risk, and different cancer types. Literature search was performed using the electronic databases MEDLINE, SCOPUS and EMBASE until January 10, 2014. Inclusion criteria were cohort or case–control studies. Study specific risk ratios (RRs) were pooled using a random effect model by the Cochrane software package Review Manager 5.2. Twenty‐one cohort studies including 1,368,736 subjects and 12 case–control studies with 62,725 subjects met the objectives and were enclosed for meta‐analyses. The highest adherence to MD category resulted in a significantly risk reduction for overall cancer mortality/incidence (cohort; RR: 0.90, 95% CI 0.86–0.95, p < 0.0001; I² = 55%), colorectal (cohort/case–control; RR: 0.86, 95% CI 0.80–0.93, p < 0.0001; I² = 62%], prostate (cohort/case–control; RR: 0.96, 95% CI 0.92–0.99, p = 0.03; I² = 0%) and aerodigestive cancer (cohort/case–control; RR: 0.44, 95% CI 0.26–0.77, p = 0.003; I² = 83%). Nonsignificant changes could be observed for breast cancer, gastric cancer and pancreatic cancer. The Egger regression tests provided limited evidence of substantial publication bias. High adherence to a MD is associated with a significant reduction in the risk of overall cancer mortality (10%), colorectal cancer (14%), prostate cancer (4%) and aerodigestive cancer (56%).     

Association between adult weight gain and colorectal cancer: A dose–response meta‐analysis of observational studies

This study investigated the association between adult weight gain and risk of colorectal cancer (CRC). Using terms related to weight gain and CRC, we searched PubMed, Embase and Web of Science for relevant studies published before June 2014. Two evaluators independently selected studies according to the selection criteria, and eight studies were included (three case–control and five cohort studies). Summary estimates were obtained using fixed‐ or random‐effects models. The relative risk (RR) of the association between adult weight gain and CRC was 1.25 (95% confidence interval [CI], 1.10–1.43); the RR was 1.30 (95% CI, 1.14–1.49) for colon cancer (CC) and 1.27 (95% CI, 1.02–1.58) for rectal cancer (RC) for the highest versus lowest category. For every 5‐kg increase in adult weight, the risk increased by 5% (RR, 1.05; 95% CI, 1.02–1.09) for CRC, 6% (RR, 1.06; 95% CI, 1.02–1.11) for CC and 6% (RR, 1.06; 95% CI, 1.03–1.08) for RC. The subgroup analyses showed a positive association between adult weight gain and risk of CRC only in men, and the RR was 1.65 (95% CI, 1.42–1.92) for the highest versus lowest category of adult weight gain and 1.10 (95% CI, 1.06–1.15) for a 5‐kg increase in adult weight. In conclusion, there is evidence that adult weight gain is associated with an increased risk of CRC. However, the positive association between adult weight gain and risk of CRC is stronger among men than among women.     

Meta‐analysis of the association between dietary inflammatory index (DII) and cancer outcomes

Proinflammatory dietary patterns have been associated with increased cancer risk and mortality. We present a systematic review and meta‐analysis of the current published literature on a dietary inflammatory index (DII) score and its association with cancer risk and mortality outcomes. Published articles from online databases (PubMed, Scopus, and Embase) examining the association between DII and any cancer risk, incidence, or mortality between 1980 and November 2016 were selected for review. Results of studies meeting inclusion criteria were summarized and meta‐analyzed using STATA to generate summary measures of association across studies. Sixty‐three published articles were identified from the search, and following title, abstract and full‐text review, twenty‐four studies met inclusion criteria. All articles calculated DII scores based on study‐specific food‐frequency questionnaires using methodology from the same article. Of the 24 included studies, 13 were case–control, 6 were prospective cohort, 1 was a retrospective cohort, 3 were RCTs, and 1 did not specify study design. The most common cancers examined were colorectal, breast, lung, and prostate. Individuals in the highest versus lowest DII categories had 25% increased risk of overall cancer incidence (RR: 1.25, 95% CI: 1.16–1.35), 75% higher odds of cancer (OR: 1.75, 95% CI: 1.43–2.16) and 67% increased risk of cancer mortality (RR: 1.67, 95% CI: 1.13–2.48). Upon stratification for cancer type, positive associations remained (RR_breast: RR: 1.12, 95% CI: 1.03–1.22) (RR_colorectal: 1.33, 95% CI: 1.22–1.46) (RR_lung: 1.30, 95% CI: 1.13–1.50). There were consistent and significant positive associations between higher DII and cancer incidence and mortality across cancer types, study populations, and study design.     

Coffee drinking and risk of endometrial cancer—A population‐based cohort study

Coffee drinking has been reported to have beneficial effects on insulin resistance, which has been directly associated with endometrial cancer. Although a relationship between coffee consumption and endometrial cancer risk is biologically plausible, this hypothesis has been previously explored in only 2 prospective studies, with a small number of cases. We used data from the Swedish Mammography Cohort, a population‐based prospective cohort study of 60,634 women. During 17.6 years of follow‐up, 677 participants were diagnosed with incident endometrial cancer (adenocarcinoma). We examined the association between self‐reported coffee consumption (at baseline 1987–90 and in 1997) and endometrial cancer risk using Cox proportional hazards models. Each additional cup (200 g) of coffee per day was associated with a rate ratio (RR) of 0.90 [95% confidence interval (CI), 0.83–0.97]. In women drinking 4 or more cups of coffee a day, the RR for the risk reduction of endometrial cancer was 0.75 (95% CI, 0.58–0.97) when compared with those who drank 1 cup or less. The association seemed largely confined to overweight and obese women, who showed a respective risk reduction of 12% (95% CI, 0–23%) and 20% (95% CI, 7–31%) for every cup of coffee, but was not observed among normal‐weight women. There was a statistically significant interaction between coffee consumption and body mass index (p_interaction < 0.001). These data indicate that coffee consumption may be associated with decreased risk of endometrial cancer, especially among women with excessive body weight. If confirmed by other prospective studies, these results are of major public health significance. © 2009 UICC     

Coffee Consumption and Pancreatic Cancer Risk: A Meta-Epidemiological Study of Population-based Cohort Studies

Objective: Previous systematic reviews evaluating the association between coffee consumption and pancreatic cancer showed inconsistent results. The aim was to conduct a meta-epidemiological study to explore further the association between coffee consumption and the incidence of pancreatic cancer. Methods: The selection criteria were defined as a population-based prospective cohort study reporting adjusted relative risk (RR) and their 95% confidence interval (95%CI) of pancreatic cancer occurrence according to coffee consumption. Adjusted RR for the highest versus the lowest level of coffee consumption in each study was extracted. A fixed-effect model was applied to calculate a summary RR (sRR) and its 95%CI. Two-stage random-effects dose-response meta-analysis (DRMA) was performed to estimate the incidence risk per unit dose (cup per day). Results: Twelve cohort studies were selected for meta-analysis. The total number of cohort participants was 3,230,053, and pancreatic cancer incidents were 10,587. The sRR of pancreatic cancer risk for the highest versus the lowest level of coffee consumption indicated no statistical significance (sRR=0.98, 95% CI: 0.88-1.10; I-squared=0.0%). Two-stage random-effect DRMA showed the non-linear relationship between the amount of coffee consumption and pancreatic cancer risk. And the RR for an increment of one cup per day of coffee consumption was 0.97 (95%CI: 0.91-1.04, P=0.42), without statistically significant. Conclusion: There was no association between coffee consumption habits and pancreatic cancer risk. And there was no statistical significance in the dose-response relationship between the amount of coffee consumption and pancreatic cancer risk. Finding the turning point would be important because it can be critical information for the prevention of pancreatic cancer.     

Analgesic use and the risk of kidney cancer: A meta‐analysis of epidemiologic studies

Analgesics are the most commonly used over‐the‐counter drugs worldwide with certain analgesics having cancer prevention effect. The evidence for an increased risk of developing kidney cancer with analgesic use is mixed. Using a meta‐analysis design of available observational epidemiologic studies, we investigated the association between analgesic use and kidney cancer risk. We searched the MEDLINE and EMBASE databases to identify eligible case–control or cohort studies published in English until June 2012 for three categories of analgesics: acetaminophen, aspirin or other non‐steroidal anti‐inflammatory drugs (NSAIDs). Study‐specific effect estimates were pooled to compute an overall relative risk (RR) and its 95% confidence interval (CI) using a random‐effects model for each category of the analgesics. We identified 20 studies (14 with acetaminophen, 13 with aspirin and five with other NSAIDs) that were performed in six countries, including 8,420 cases of kidney cancer. Use of acetaminophen and non‐aspirin NSAIDs were associated with an increased risk of kidney cancer (pooled RR: 1.28; 95% CI: 1.15–1.44 and 1.25; 95% CI: 1.06–1.46, respectively). For aspirin use, we found no overall increased risk (pooled RR: 1.10; 95% CI: 0.95–1.28), except for non‐US studies (five studies, pooled RR: 1.17; 95% CI: 1.04–1.33). Similar increases in risks were seen with higher analgesic intake. In this largest meta‐analysis to date, we found that acetaminophen and non‐aspirin NSAIDs are associated with a significant risk of developing kidney cancer. Further work is needed to elucidate biologic mechanisms behind these findings.     

Coffee consumption and risk of colorectal cancer in a population-based prospective cohort of Japanese men and women

We prospectively examined the association between coffee consumption and the risk of developing colorectal cancer in a large population-based cohort study (the JPHC Study) of Japanese men and women. Data were analyzed from a population-based cohort of 96,162 subjects (46,023 men and 50,139 women). A total of 1,163 incident colorectal cancers were identified during the follow-up period, including 763 cases of colon cancer and 400 of rectal cancer. We observed a significant inverse association between coffee consumption and the risk of developing invasive colon cancer among women. Compared with those who almost never consumed coffee, women who regularly consumed 3 or more cups of coffee per day had a RR of 0.44 (95% CI = 0.19-1.04; p for trend = 0.04) after adjustment for potential confounding factors. However, no significant association was found for rectal cancer in women. In men, no significant decrease was observed in any colorectal cancer site. Further, additional analyses on the association of green tea consumption with colorectal cancer risk found no significant association in men or women. These findings suggest that coffee consumption may lower the risk of colon cancer among Japanese women.     

Obesity and incidence of lung cancer: A meta‐analysis

To date, the relationship between obesity and the incidence of lung cancer remains unclear and inconclusive. Thus, we conducted a meta‐analysis of published studies to provide a quantitative evaluation of this association. Relevant studies were identified through PubMed and EMBASE databases from 1966 to December 2011, as well as through the reference lists of retrieved articles. A total of 31 articles were included in this meta‐analysis. Overall, excess body weight (body mass index, BMI ≥ 25 kg/m²) was inversely associated with lung cancer incidence (relative risk, RR = 0.79; 95% confidence interval, CI: 0.73–0.85) compared with normal weight (BMI = 18.5‐24.9 kg/m²). The association did not change with stratification by sex, study population, study design, and BMI measurement method. However, when stratified by smoking status, the inverse association between excess body weight and lung cancer incidence in current (RR = 0.63, 95% CI: 0.57–0.70) and former (RR = 0.73, 95% CI: 0.58–0.91) smokers was strengthened. In non‐smokers, the association was also statistically significant (RR = 0.83, 95% CI: 0.70–0.98), although the link was weakened to some extent. The stratified analyses also showed that excess body weight was inversely associated with squamous cell carcinoma (RR = 0.68, 95% CI: 0.58–0.80) and adenocarcinoma (RR = 0.79, 95% CI: 0.65–0.96). No statistically significant link was found between excess body weight and small cell carcinoma (RR = 0.99, 95% CI: 0.66–1.48). The results of this meta‐analysis indicate that overweight and obesity are protective factors against lung cancer, especially in current and former smokers.     

Coffee consumption and the risk of colorectal cancer by anatomical subsite in Japan: Results from the HERPACC studies

Consumption of coffee, a popular beverage worldwide, has been associated with lower colorectal cancer (CRC) risk. Although CRC exhibits different biological characteristics by anatomical subsite, the possibly heterogeneous impact of coffee on CRC by anatomical subsite has remained unclear. Here, we conducted two case‐control studies to examine the association between coffee consumption and CRC risk as well as risk by anatomic subsite among Japanese using data from the Hospital‐based Epidemiological Research Program at Aichi Cancer Center I and II (HERPACC‐I and II). Subjects were enrolled in HERPACC‐I between 1988 and 2000 and in HERPACC‐II between 2001 and 2005. Coffee consumption was measured with a self‐administered questionnaire. A conditional logistic regression model was used to calculate odds ratios (ORs) of CRC with coffee consumption, adjusted for potential confounders of age, smoking, alcohol drinking, red meat intake, BMI, exercise, family history of CRC, and diabetes mellitus history. We estimated summary ORs by pooling study‐specific ORs with a fixed effects model. In total, 2,696 CRC cases and 13,480 non‐cancer outpatients as controls were included. Overall, compared to non‐drinkers, ORs of less than 1 cup/day, 1–2 cups/day and 3 or more cups/day for CRC were 0.88 (95% CI: 0.77–1.00), 0.90 (95% CI: 0.80–1.01) and 0.78 (95% CI: 0.65–0.92), respectively (trend‐p = 0.009). Subsite‐specific analysis revealed a significant inverse linear trend between coffee consumption and distal colon cancer (p‐trend = 0.048), and a tendency toward a lower risk of rectal cancer (p‐trend = 0.068). These findings suggest that coffee consumption might impact the prevention of CRC, especially distal colon cancer.     

Association between height and thyroid cancer risk: A meta‐analysis of prospective cohort studies

While several epidemiological studies have investigated the relationship between height and risk for thyroid cancer, the results were inconsistent. In the present study, a systematic review and meta‐analysis of prospective cohort studies was conducted to assess the impact of height on thyroid cancer risk. Online databases were searched up to December 30, 2014, for prospective cohort studies on the association between height and thyroid cancer risk. Pooled relative risks (RRs) and 95% confidence intervals (CIs) were calculated using a random‐effects model of meta‐analysis. In all, 11 articles were included in this meta‐analysis, including 15 prospective cohort studies, containing 6,695,593 participants and 7,062 cases of thyroid cancer. By comparing the highest versus the lowest categories of height, we reported that risk of thyroid cancer was increased with height in both men (summary RR = 1.40, 95%CI 1.09–1.78, p = 0.008) and women (summary RR = 1.54, 95%CI 1.30–1.83, p < 0.001). The summary RR of thyroid cancer per 5‐cm increase in height was 1.16 (95%CI 1.09–1.23, p < 0.001). The results were similar among men (per 5‐cm increase RR = 1.13, 95%CI 1.03–1.23, p = 0.011) and women (per 5‐cm increase RR = 1.18, 95%CI 1.10–1.27, p < 0.001). No obvious risk of publication bias was observed. Our meta‐analysis provides strong evidence for a dose–response relationship between height and risk of thyroid cancer in both men and women.     

Prospective study of breast cancer in relation to coffee,tea and caffeine in Sweden

Studies of coffee and tea consumption and caffeine intake as risk factors for breast cancer are inconclusive. We assessed coffee and tea consumption, caffeine intake, and possible confounding factors among 42,099 women from the Swedish Women's Lifestyle and Health study, the participants of which were aged 30–49 years at enrollment in 1991–1992. Complete follow‐up for breast cancer incidence was performed through 2012 via linkage to national registries. Poisson regression models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs) for breast cancer. During follow‐up 1,395 breast cancers were diagnosed. The RR was 0.97 (95% CI 0.94–0.99) for a 1‐unit increase in cups of coffee/day, 1.14 (95% CI 1.05–1.24) for a 1‐unit increase in cups of tea/day, and 0.97 (95% CI 0.95–1.00) for a 100 mg/day increase in caffeine intake. Although the RR for no consumption (RR = 0.86, 95% CI 0.69–1.08), a group with a relatively small number of women, was not statistically significant, women with higher consumption had a decreased breast cancer risk (3–4 cups/day: RR = 0.87, 95% CI 0.76–1.00; ≥5 cups/day: RR = 0.81, 95% CI 0.70–0.94) compared to women consuming 1–2 cups of coffee/day. Compared to no consumption, women consuming >1 cups tea/day showed an increased breast cancer risk (RR = 1.19, 95% CI 1.00–1.42). Similar patterns of estimates were observed for breast cancer risk overall, during pre‐ and postmenopausal years, and for ER+ or PR+ breast cancer, but not for ER? and PR? breast cancer. Our findings suggest that coffee consumption and caffeine intake is negatively associated with the risk of overall and ER+/PR? breast cancer, and tea consumption is positively associated with the risk of overall and ER+/PR+ breast cancer.     

Age at menarche and risk of ovarian cancer: A meta‐analysis of epidemiological studies

Epidemiological studies have reported inconsistent associations between menarcheal age and ovarian cancer risk. To our knowledge, a meta‐analysis for the association between menarcheal age and ovarian cancer has not been reported. Relevant published studies of menarcheal age and ovarian cancer were identified using MEDLINE, EMBASE and Web of Science through the end of April 2012. Two authors (T‐T.G. and Q‐J.W.) independently assessed eligibility and extracted data. We pooled the relative risks (RRs) from individual studies using a random‐effects model and performed heterogeneity and publication bias analyses. A total of 27 observational studies consisting of 22 case–control and five cohort studies were included in our analysis. In a pooled analysis of all studies, a statistically significant inverse association was observed between menarcheal age (for the oldest compared to the youngest category) and ovarian cancer risk (RR = 0.85; 95% confidence interval [CI] = 0.75–0.97). The pooled RRs of ovarian cancer for the oldest versus the youngest categories of menarcheal age in prospective and case–control studies were 0.89 (95% CI = 0.76–1.03) and 0.84 (95% CI = 0.70–0.99), respectively. Inverse associations between menarcheal age and ovarian cancer risk were observed in most subgroups; however, the significant association was restricted to invasive and borderline serous ovarian cancer. In conclusion, findings from this meta‐analysis support that menarcheal age was inversely associated with the risk of ovarian cancer. More large studies are warranted to stratify these results by different cancer grading and histotype of ovarian cancer.     

Alcohol drinking and pancreatic cancer risk: a meta‐analysis of the dose‐risk relation

In order to provide a more precise quantification of the association between alcohol consumption and pancreatic cancer risk, we performed a meta‐analysis of relevant dose‐risk results. We conducted a PubMed search of all case‐control (N=21) and cohort (N=11) studies published up to March 2009. We computed summary relative risk (RR) estimates using either fixed‐ or, in the presence of heterogeneity, random‐effects models. The pooled RR was 0.92 (95% confidence interval, 95% CI, 0.86–0.97) for <3 drinks/day and 1.22 (95% CI, 1.12–1.34) for ≥3 drinks/day. The increased risk for heavy drinking was similar in women and men, but apparently stronger in cohort studies (RR=1.29), in studies with high quality index (RR=1.30), and did not appear to be explained by residual confounding by either history of pancreatitis or tobacco smoking. This meta‐analysis provides strong evidence for the absence of a role of moderate drinking in pancreatic carcinogenesis, coupled to an increased risk for heavy alcohol drinking. Given the moderate increase in risk and the low prevalence of heavy drinkers in most populations, alcohol appears to be responsible only for a small fraction of all pancreatic cancers.     

Egg consumption and breast cancer risk: a meta-analysis

The relationship between egg consumption and breast cancer risk has been inconsistent, so it is necessary to conduct a meta-analysis to evaluate the relationship. PubMed, EMBASE and ISI Web of Knowledge were searched to find cohort studies or case control studies that evaluated the relationship between egg consumption and breast cancer risk. A comprehensive meta-analysis software was used to conduct the meta-analysis. 13 studies were included. The meta-analysis results showed that egg consumption was associated with increased breast cancer risk (RR 1.04, 95 % CI 1.01–1.08). Subgroup analyses showed egg consumption was also associated with increased breast cancer risk based on cohort studies (RR 1.04, 95 % CI 1.00–1.08), among European population (RR 1.05, 95 % CI 1.01–1.09), Asian population (RR 1.09, 95 % CI 1.00–1.18), postmenopausal population (RR 1.06, 95 % CI 1.02–1.10), and those who consumed ≥2, ≤5/week (RR 1.10, 95 % CI 1.02–1.17), but not in case–control studies (RR 1.06, 95 % CI 0.97–1.15), among American population (RR 1.04, 95 % CI 0.94–1.16), premenopausal population (RR 1.04, 95 % CI 0.98–1.11) and those who consumed ≥1, <2/week (RR 1.04, 95 % CI 0.97–1.11) or >5 eggs/week (RR 0.97, 95 % CI 0.88–1.06). Egg consumption was associated with increased breast cancer risk among the European, Asian and postmenopausal population and those who consumed ≥2, ≤5/week.     

Body fatness at an early age and risk of colorectal cancer

While there is convincing evidence that excess body fatness in adulthood is positively associated with colorectal cancer risk, the association between body fatness at an early age (≤30 years) and the risk of colorectal cancer has been equivocal. The present meta‐analysis was performed to clarify this association. PubMed and Web of Science databases were searched for relevant studies that investigated this association. The risk estimates from each study were transformed into a continuous variable for each 5 kg/m² increase in body mass index (BMI). A random effects model was used to calculate the summary relative risks (RRs) with 95% confidence intervals (CIs). A total of 15 observational studies (13 cohort studies and two case‐control studies) were included in this meta‐analysis. Each 5 kg/m² increase in BMI was significantly associated with a 13% (RR 1.13, 95% CI 1.08, 1.19), 17% (RR 1.17, 95% CI 1.09, 1.25) and 8% (RR 1.08, 95% CI 1.04, 1.11) higher risk of colorectal cancer overall, in men, and in women, respectively. Substantial heterogeneity was observed across studies. Based on the anatomic subsite, each 5 kg/m² increase in BMI was significantly associated with a 14% (RR 1.14, 95% CI 1.07, 1.22) higher risk of colon cancer, whereas no association (RR 1.03, 95% CI 0.95, 1.13) was observed with rectal cancer. In summary, body fatness at an early age may affect colon cancer risk later in life. Prevention of overweight and obesity in young individuals should be emphasized to prevent early‐onset colon cancer attributed to excess body fatness.