Lifestyle Risk Factors for Serrated Colorectal Polyps: A Systematic Review and Meta-analysis.
Plain language summary
Colorectal cancer (CRC) is a heterogeneous disease thought to result from the accumulation of various aberrant mutations in the cells lining the colorectal mucosa. The aim of this systematic review and meta-analysis was to evaluate modifiable and lifestyle factors and the risk of serrated polyps (a type of growth that stick out from the surface of the colon or rectum) of the colorectum. A search of 3 databases yielded a potential 2446 studies for inclusion, from which 43 remained for systematic review. Results indicate that smoking, alcohol consumption, body fatness, dietary fat and meat consumption increased the risk of developing serrated polyps. Whereas, nonsteroidal anti-inflammatory drugs, aspirin and dietary folate decreased this risk. Authors conclude that their findings strengthen public health messages promoting awareness and change in order to reduce the risk of these precancerous lesions and consequently CRC.
BACKGROUND & AIMS Certain subsets of colorectal serrated polyps (SP) have malignant potential. We performed a systematic review and meta-analysis to investigate the association between modifiable lifestyle factors and risk for SPs. METHODS We conducted a systematic search of Medline, Embase, and Web of Science for observational or interventional studies that contained the terms risk or risk factor, and serrated or hyperplastic, and polyps or adenomas, and colorectal (or synonymous terms), published by March 2016. Titles and abstracts of identified articles were independently reviewed by at least 2 reviewers. Adjusted relative risk (RR) and 95% confidence interval (CI) were combined using random effects meta-analyses to assess the risk of SP, when possible. RESULTS We identified 43 studies of SP risk associated with 7 different lifestyle factors: smoking, alcohol, body fatness, diet, physical activity, medication, and hormone-replacement therapy. When we compared the highest and lowest categories of exposure, factors we found to significantly increase risk for SP included tobacco smoking (RR, 2.47; 95% CI, 2.12-2.87), alcohol intake (RR, 1.33; 95% CI, 1.17-1.52), body mass index (RR, 1.40; 95% CI, 1.22-1.61), and high intake of fat or meat. Direct associations for smoking and alcohol, but not body fat, tended to be stronger for sessile serrated adenomas/polyps than hyperplastic polyps. In contrast, factors we found to significantly decrease risks for SP included use of nonsteroidal anti-inflammatory drugs (RR, 0.77; 95% CI, 0.65-0.92) or aspirin (RR, 0.81; 95% CI, 0.67-0.99), as well as high intake of folate, calcium, or fiber. No significant associations were detected between SP risk and physical activity or hormone replacement therapy. CONCLUSIONS Several lifestyle factors, most notably smoking and alcohol, are associated with SP risk. These findings enhance our understanding of mechanisms of SP development and indicate that risk of serrated pathway colorectal neoplasms could be reduced with lifestyle changes.
Risk factors for pancreatic cancer: a summary review of meta-analytical studies.
International journal of epidemiology. 2015;44(1):186-98
Plain language summary
Pancreatic cancer (PC) is one of the four or five most common causes of cancer mortality in developed countries. The aim of this review was to summarize results from pooled analyses and meta-analyses to estimate the fraction of PCs attributable to many different risk factors. A comprehensive review of the literature was carried out by searching for meta-analytical studies on the association between specific risk factors and PC risk or multiple cancer sites. Results indicate that PC has a multifactorial aetiology. All identified factors can be combined into a specific aetiological (the philosophy or study of causation) pathway for PC. The main pathways include insulin resistance (central adiposity, diabetes, metabolic syndrome), inflammation (tobacco, alcohol, pancreatitis), DNA damage (tobacco, red meat) and haemostasis (blood group, history of thrombosis). Authors conclude that about two-thirds of the major risk factors associated with PC are potentially modifiable, affording a unique opportunity for preventing one of our deadliest cancers.
BACKGROUND The aetiology of pancreatic cancer (PC) has been extensively studied and is the subject of numerous meta-analyses and pooled analyses. We have summarized results from these pooled and meta-analytical studies to estimate the fraction of PCs attributable to each of the identified risk factors. METHODS Using a comprehensive strategy, we retrieved 117 meta-analytical or pooled reports dealing with the association between specific risk factors and PC risk. We combined estimates of relative risk and estimates of exposure to calculate the fraction of PCs caused or prevented by a particular exposure. RESULTS Tobacco smoking ('strong' evidence) and Helicobacter pylori infection ('moderate' evidence) are the major risk factors associated with PC, with respective estimated population attributable fractions of 11-32% and 4-25%. The major protective factors are history of allergy ('strong' evidence) and increasing fruit or folate intake ('moderate' evidence), with respective population preventable fractions of 3-7% and 0-12%. CONCLUSIONS We summarized results of 117 meta-analytical or pooled data reports dealing with 37 aetiological exposures, to obtain robust information about the suspected causes of PC. By combining these estimates with their prevalences in the population, we calculated population attributable or population preventable fractions. About two-thirds of the major risk factors associated with PC are potentially modifiable, affording a unique opportunity for preventing one of our deadliest cancers.