Theoretical attributable risk analysis and Disability Adjusted Life Years (DALYs) based on increased dairy consumption.

BACKGROUND: Identification of modifiable risk factors that may impact chronic disease risk is critical to public health. Our study objective was to conduct a theoretical population attributable risk analysis to estimate the burden of disease from low dairy intake and to estimate the impact of increased dairy intake on United States (US)-based disability adjusted life years (DALYs). METHODS: We conducted a comprehensive literature review to identify statistically significant summary relative risk estimates (SRREs) from recent meta-analyses of dairy consumption and key chronic disease outcomes. The SRREs were applied to preventive fractions using a range of categories (low to high) for population consumption of dairy products. The preventive fraction estimates were then applied to the number of DALYs for each health outcome in the US based on 2019 WHO estimates. The population attributable risk proportion estimates were calculated using the inverse of the SRRE from each meta-analysis using the same range of categories of consumption. These values were subsequently applied to the DALYs estimates to estimate the theoretical burden of disease attributable to low dairy intake. RESULTS: Statistically significant SRREs were identified in recent meta-analyses of total dairy consumption in relation to breast cancer, colorectal cancer, cardiovascular disease (CVD), type 2 diabetes (T2D), stroke, and hypertension. In this theoretical analysis, nearly 850,000 DALYs (or 5.0% of estimated years of healthy life lost) due to CVD and 200,000 DALYs (4.5%) due to T2D may be prevented by increased dairy consumption. Approximately 100,000 DALYs due to breast cancer (7.5%) and approximately 120,000 DALYs (8.5%) due to colorectal cancer may be prevented by high dairy intake. The numbers of DALYs for stroke and hypertension that may be prevented by increased dairy consumption were approximately 210,000 (6.0%) and 74,000 (5.5%), respectively. CONCLUSIONS: Consumption of dairy products has been associated with decreased risk of multiple chronic diseases of significant public health importance. The burden of disease that may potentially be prevented by increasing dairy consumption is substantial, and population-wide improvement in meeting recommended daily dairy intake goals could have a notable public health impact. However, this analysis is theoretical, and thus additional studies providing empirical evidence are needed to further clarify potential relationships between dairy intake and various health outcomes.

Epidemiology of lung cancer among acrylonitrile-exposed study populations: A meta-analysis.

PURPOSE: To conduct a systematic review and meta-analysis of lung cancer among acrylonitrile-exposed workers. METHODS: A literature search through April 2020 was performed to identify relevant cohort and case-control studies. Data from these studies were meta-analyzed to generate summary relative risk estimates (SRREs). Heterogeneity was examined in sub-group and sensitivity analyses, and by meta-regression. RESULTS: Twenty-two studies were reviewed systematically, and 10 cohort studies and one case-control study were meta-analyzed. Individual relative risk estimates reported across studies were heterogeneous, with most being relatively weak in statistical strength and non-statistically significant on both sides of the null value. Meta-analysis of these data resulted in an SRRE of 1.04 (95% CI: 0.89-1.21; overall model, largely consisting of all workers exposed to acrylonitrile). Sub-group analyses and meta-regression did not support patterns of positive dose-response relationships by duration of exposure/employment or cumulative exposure. CONCLUSIONS: Although some positive associations have been reported in internal comparison analyses based on increasing exposure categories, few associations are statistically significant, there are no apparent or consistent patterns of dose-response, and the confounding influence of cigarette smoking was not adequately controlled. Thus, findings from this review and meta-analysis do not support an increased risk of lung cancer among acrylonitrile workers.

Factors Associated with Breastfeeding Initiation and Continuation: A Meta-Analysis.

OBJECTIVE: To use a quantitative approach to evaluate the literature for quantity, quality, and consistency of studies of maternal and infant characteristics in association with breastfeeding initiation and continuation, and to conduct a meta-analysis to produce summary relative risks (RRs) for selected factors. STUDY DESIGN: A systematic review using PubMed and CINAHL through March 2016 was conducted to identify relevant observational studies in developed nations, reporting a measure of risk for 1 or more of 6 quantitatively derived, high impact factors in relation to either breastfeeding initiation or continuation. One author abstracted data using a predesigned database, which was reviewed by a second independent author; data evaluation and interpretation included all co-authors. These factors were summarized using standard meta-analysis techniques. RESULTS: Six high impact factors were identified (smoking [39 papers], mode of delivery [47 papers], parity [31 papers], dyad separation [17 papers], maternal education [62 papers], and maternal breastfeeding education [32 papers]). Summary RR from random-effects models for breastfeeding initiation were highest for high vs low maternal education (RR 2.28 [95% CI 1.92-2.70]), dyad connection vs not (RR 2.01 [95% CI 1.38-2.92]), and maternal nonsmoking vs smoking (RR = 1.76 [95% CI 1.59-1.95]); results were similar for breastfeeding continuation. CONCLUSIONS: Despite methodological heterogeneity across studies, relatively consistent results were observed for these perinatally identifiable factors associated with breastfeeding initiation and continuation, which may be informative in developing targeted interventions to provide education and support for successful breastfeeding in more families.

Meta-analysis of Egg Consumption and Risk of Coronary Heart Disease and Stroke.

The possible relationship between dietary cholesterol and cardiac outcomes has been scrutinized for decades. However, recent reviews of the literature have suggested that dietary cholesterol is not a nutrient of concern. Thus, we conducted a meta-analysis of egg intake (a significant contributor to dietary cholesterol) and risk of coronary heart disease (CHD) and stroke. A comprehensive literature search was conducted through August 2015 to identify prospective cohort studies that reported risk estimates for egg consumption in association with CHD or stroke. Random-effects meta-analysis was used to generate summary relative risk estimates (SRREs) for high vs low intake and stratified intake dose-response analyses. Heterogeneity was examined in subgroups where sensitivity and meta regression analyses were conducted based on increasing egg intake. A 12% decreased risk (SRRE = 0.88, 95% confidence interval [CI], 0.81-0.97) of stroke was observed in the meta-analysis of 7 studies of egg intake (high vs low; generally 1/d vs <2/wk), with little heterogeneity (p-H = 0.37, I2 = 7.50). A nonstatistically significant SRRE of 0.97 (95% CI, 0.88-1.07, p-H = 0.67, I2 = 0.00) was observed in the meta-analysis of 7 studies of egg consumption and CHD. No clear dose-response trends were apparent in the stratified intake meta-analyses or the meta regression analyses. Based on the results of this meta-analysis, consumption of up to one egg daily may contribute to a decreased risk of total stroke, and daily egg intake does not appear to be associated with risk of CHD. Key Teaching Points: • The role of egg consumption in the risk of stroke and coronary heart disease has come under scrutiny over many years. • A comprehensive meta-analysis of prospective cohort studies that reported risk estimates for egg consumption in association with CHD or stroke was performed on the peer-reviewed epidemiologic literature through August 2015. • Overall, summary associations indicate that intake of up to 1 egg daily may be associated with reduced risk of total stroke. • Overall, summary associations show no clear association between egg intake and increased or decreased risk of CHD. • Eggs are a relatively low-cost and nutrient-dense whole food that provides a valuable source of protein, essential fatty acids, antioxidants, choline, vitamins, and minerals.

Dairy consumption and CVD: a systematic review and meta-analysis.

Inverse associations between dairy consumption and CVD have been reported in several epidemiological studies. Our objective was to conduct a meta-analysis of prospective cohort studies of dairy intake and CVD. A comprehensive literature search was conducted to identify studies that reported risk estimates for total dairy intake, individual dairy products, low/full-fat dairy intake, Ca from dairy sources and CVD, CHD and stroke. Random-effects meta-analyses were used to generate summary relative risk estimates (SRRE) for high v. low intake and stratified intake dose-response analyses. Additional dose-response analyses were performed. Heterogeneity was examined in sub-group and sensitivity analyses. In total, thirty-one unique cohort studies were identified and included in the meta-analysis. Several statistically significant SRRE below 1.0 were observed, namely for total dairy intake and stroke (SRRE=0·91; 95% CI 0·83, 0·99), cheese intake and CHD (SRRE=0·82; 95% CI 0·72, 0·93) and stroke (SRRE=0·87; 95% CI 0·77, 0·99), and Ca from dairy sources and stroke (SRRE=0·69; 95% CI 0·60, 0·81). However, there was little evidence for inverse dose-response relationships between the dairy variables and CHD and stroke after adjusting for within-study covariance. The results of this meta-analysis of prospective cohort studies have shown that dairy consumption may be associated with reduced risks of CVD, although additional data are needed to more comprehensively examine potential dose-response patterns.

Mesothelioma among Motor Vehicle Mechanics: An Updated Review and Meta-analysis.

BACKGROUND: We published a meta-analysis of the association between work as a motor vehicle mechanic and mesothelioma in 2004. Since then, several relevant studies on this topic have been published. Thus, to update the state-of-the-science on this issue, we conducted a new systematic review and meta-analysis. METHODS: A comprehensive PubMed literature search through May 2014 was conducted to identify studies that reported relative risk estimates for mesothelioma among motor vehicle mechanics (in general), and those who were engaged in brake repair (specifically). Studies were scored and classified based on study characteristics. Random-effects meta-analyses generated summary relative risk estimates (SRREs) and corresponding 95% confidence intervals (CI). Heterogeneity of results was examined by calculating Q-test P-values (P-H) and I (2) estimates. Sub-group and sensitivity analyses were conducted for relevant study characteristics and quality measures. RESULTS: Ten case-control studies, one cohort study, and five proportionate mortality ratio (PMR)/standardized mortality odds ratio (SMOR) studies were identified and included in the quantitative assessment. Most meta-analysis models produced SRREs below 1.0, and no statistically significant increases in mesothelioma were observed. The SRRE for all studies was 0.80 (95% CI: 0.61-1.05) with significant heterogeneity (P-H <0.001, I (2) = 62.90). A similar SRRE was observed among the five Tier 1 studies with the highest quality ratings (SRRE = 0.76, 95% CI: 0.46-1.25), with no heterogeneity among studies (P-H = 0.912, I (2) = 0.00). Meta-analysis of the Tier 2 (n = 5) and Tier 3 (n = 6) studies resulted in SRREs of 1.09 (95% CI: 0.76-1.58) and 0.73 (95% CI: 0.49-1.08), respectively. Restricting the analysis to Tiers 1 and 2 combined resulted in an SRRE of 0.92 (95% CI: 0.72-1.29). The SRRE specific to brake work (n = 4) was 0.64 (95% CI: 0.38-1.09). CONCLUSIONS: This meta-analysis of the epidemiologic studies provides evidence that motor vehicle mechanics, including workers who were engaged in brake repair, are not at an increased risk of mesothelioma.

Meta-Analysis of Long-Chain Omega-3 Polyunsaturated Fatty Acids (LCω-3PUFA) and Prostate Cancer.

We conducted a systematic review and meta-analysis to estimate the potential association between LCω-3PUFAs and prostate cancer (PC). A comprehensive literature search was performed through 2013 to identify prospective studies that examined dietary intakes of long-chain omega-3 polyunsaturated fatty acids (LCω-3PUFA) or blood biomarkers of LCω-3PUFA status and risk of PC. Random-effects meta-analyses were conducted to generate summary relative risk estimates (SRREs) for LCω-3PUFAs and total PC, and by stage and grade. Subgroup analyses were also conducted for specific fatty acids and other study characteristics. Twelve self-reported dietary intake and 9 biomarker studies from independent study populations were included in the analysis, with 446,243 and 14,897 total participants, respectively. No association between LCω-3PUFAs and total PC was observed (SRRE = 1.00, 95% CI: 0.93-1.09) for the dietary intake studies (high vs. low LCω-3PUFAs category comparison) or for the biomarker studies (SRRE of 1.07, 95% CI: 0.94-1.20). In general, most summary associations for the dietary intake studies were in the inverse direction, whereas the majority of summary associations for the biomarker studies were in the positive direction, but all were weak in magnitude. The results from this meta-analysis do not support an association between LCω-3PUFAs and PC.

Red Meat and Colorectal Cancer: A Quantitative Update on the State of the Epidemiologic Science.

The potential relationship between red meat consumption and colorectal cancer (CRC) has been the subject of scientific debate. Given the high degree of resulting uncertainty, our objective was to update the state of the science by conducting a systematic quantitative assessment of the epidemiologic literature. Specifically, we updated and expanded our previous meta-analysis by integrating data from new prospective cohort studies and conducting a broader evaluation of the relative risk estimates by specific intake categories. Data from 27 independent prospective cohort studies were meta-analyzed using random-effects models, and sources of potential heterogeneity were examined through subgroup and sensitivity analyses. In addition, a comprehensive evaluation of potential dose-response patterns was conducted. In the meta-analysis of all cohorts, a weakly elevated summary relative risk was observed (1.11, 95% CI: 1.03-1.19); however, statistically significant heterogeneity was present. In general, summary associations were attenuated (closer to the null and less heterogeneous) in models that isolated fresh red meat (from processed meat), adjusted for more relevant factors, analyzed women only, and were conducted in countries outside of the United States. Furthermore, no clear patterns of dose-response were apparent. In conclusion, the state of the epidemiologic science on red meat consumption and CRC is best described in terms of weak associations, heterogeneity, an inability to disentangle effects from other dietary and lifestyle factors, lack of a clear dose-response effect, and weakening evidence over time. KEY TEACHING POINTS: •The role of red meat consumption in colorectal cancer risk has been widely contested among the scientific community.•In the current meta-analysis of red meat intake and colorectal cancer, we comprehensively examined associations by creating numerous sub-group stratifications, conducting extensive sensitivity analyses, and evaluating dose-response using several different methods.•Overall, all summary associations were weak in magnitude with no clear dose-response patterns.•Interpretation of findings from epidemiologic studies investigating diet and health outcomes involves numerous methodological considerations, such as accurately measuring food intake, dietary pattern differences across populations, food definitions, outcome classifications, bias and confounding, multicollinearity, biological mechanisms, genetic variation in metabolizing enzymes, and differences in analytical metrics and statistical testing parameters.

A review and meta-analysis of prospective studies of red and processed meat, meat cooking methods, heme iron, heterocyclic amines and prostate cancer.

Prostate cancer remains a significant public health concern among men in the U.S. and worldwide. Epidemiologic studies have generally produced inconclusive results for dietary risk factors for prostate cancer, including consumption of red and processed meats. We aimed to update a previous meta-analysis of prospective cohorts of red and processed meats and prostate cancer with the inclusion of new and updated cohort studies, as well as evaluate meat cooking methods, heme iron, and heterocyclic amine (HCA) intake exposure data. A comprehensive literature search was performed and 26 publications from 19 different cohort studies were included. Random effects models were used to calculate summary relative risk estimates (SRREs) for high vs. low exposure categories. Additionally, meta-regression analyses and stratified intake analyses were conducted to evaluate dose-response relationships. The SRREs for total prostate cancer and total red meat consumption, fresh red meat consumption, and processed meat consumption were 1.02 (95% CI: 0.92-1.12), 1.06 (95% CI: 0.97-1.16), and 1.05 (95% CI: 1.01-1.10), respectively. Analyses were also conducted for the outcomes of non-advanced, advanced, and fatal prostate cancer when sufficient data were available, but these analyses did not produce significant results. No significant SRREs were observed for any of the meat cooking methods, HCA, or heme iron analyses. Dose-response analyses did not reveal significant patterns of associations between red or processed meat and prostate cancer. In conclusion, the results from our analyses do not support an association between red meat or processed consumption and prostate cancer, although we observed a weak positive summary estimate for processed meats.

Effects of whey protein and resistance exercise on body composition: a meta-analysis of randomized controlled trials.

OBJECTIVES: The objective of the present meta-analysis was to examine the effect of whey protein (WP), with or without resistance exercise, on body weight and body composition in randomized controlled trials (RCTs) conducted in generally healthy adult study populations. METHODS: A comprehensive literature search was conducted to identify RCTs that investigated WP (concentrate, isolate, or hydrolystate) and body weight, body mass index (BMI), body fat, lean body mass (LBM), fat-free mass (FFM), and waist circumference. Random effects meta-analyses were conducted to generate weighted group mean differences (WGMD) for between-group comparisons (WP vs other protein sources or carbohydrates) and within-WP group comparisons (i.e., differences from baseline to trial end). Studies were classified into 2 distinct groups-WP as a supplement without dietary modification (WPS) and WP as a replacement for other sources of calories (WPR)-and were meta-analyzed separately. Subgroup analyses included examining the effect of resistance exercise and type of WP on the relationship between WP and body composition. RESULTS: Fourteen RCTs were included, with a total of 626 adult study completers. Five studies examined the effects of WPR and the remaining 9 studies examined the effects of WPS. Body weight (WGMD: -4.20 kg, 95% confidence interval [CI], -7.67, -0.73) and body fat (WGMD: -3.74 kg, 95% CI, -5.98, -1.50) were significantly decreased from baseline in the WPR within-group analyses. In the between-group analyses, the effects of WP were more favorable when compared with carbohydrates than protein sources other than whey, although findings did not reach statistical significance. Results from the subgroup analyses indicated a statistically significant increase in LBM (WGMD: 2.24 kg, 95% CI, 0.66, 3.81) among studies that included a resistance exercise component along with WP provision. CONCLUSION: The current body of literature supports the use of WP, either as a supplement combined with resistance exercise or as part of a weight loss or weight maintenance diet, to improve body composition parameters.

Cost savings of reduced constipation rates attributed to increased dietary fiber intakes: a decision-analytic model.

BACKGROUND: Nearly five percent of Americans suffer from functional constipation, many of whom may benefit from increasing dietary fiber consumption. The annual constipation-related healthcare cost savings associated with increasing intakes may be considerable but have not been examined previously. The objective of the present study was to estimate the economic impact of increased dietary fiber consumption on direct medical costs associated with constipation. METHODS: Literature searches were conducted to identify nationally representative input parameters for the U.S. population, which included prevalence of functional constipation; current dietary fiber intakes; proportion of the population meeting recommended intakes; and the percentage that would be expected to respond, in terms of alleviation of constipation, to a change in dietary fiber consumption. A dose-response analysis of published data was conducted to estimate the percent reduction in constipation prevalence per 1 g/day increase in dietary fiber intake. Annual direct medical costs for constipation were derived from the literature and updated to U.S. $ 2012. Sensitivity analyses explored the impact on adult vs. pediatric populations and the robustness of the model to each input parameter. RESULTS: The base case direct medical cost-savings was $12.7 billion annually among adults. The base case assumed that 3% of men and 6% of women currently met recommended dietary fiber intakes; each 1 g/day increase in dietary fiber intake would lead to a reduction of 1.9% in constipation prevalence; and all adults would increase their dietary fiber intake to recommended levels (mean increase of 9 g/day). Sensitivity analyses, which explored numerous alternatives, found that even if only 50% of the adult population increased dietary fiber intake by 3 g/day, annual medical costs savings exceeded $2 billion. All plausible scenarios resulted in cost savings of at least $1 billion. CONCLUSIONS: Increasing dietary fiber consumption is associated with considerable cost savings, potentially exceeding $12 billion, which is a conservative estimate given the exclusion of lost productivity costs in the model. The finding that $12.7 billion in direct medical costs of constipation could be averted through simple, realistic changes in dietary practices is promising and highlights the need for strategies to increase dietary fiber intakes.

Which design and biomaterial factors affect clinical wear performance of total disc replacements? A systematic review.

BACKGROUND: Total disc replacement was clinically introduced to reduce pain and preserve segmental motion of the lumbar and cervical spine. Previous case studies have reported on the wear and adverse local tissue reactions around artificial prostheses, but it is unclear how design and biomaterials affect clinical outcomes. QUESTIONS/PURPOSES: Which design and material factors are associated with differences in clinical wear performance (implant wear and periprosthetic tissue response) of (1) lumbar and (2) cervical total disc replacements? METHODS: We performed a systematic review on the topics of implant wear and periprosthetic tissue response using an advanced search in MEDLINE and Scopus electronic databases. Of the 340 references identified, 33 were retrieved for full-text evaluation, from which 16 papers met the inclusion criteria (12 on lumbar disc replacement and five on cervical disc replacement; one of the included studies reported on both lumbar and cervical disc replacement), which involved semiquantitative analysis of wear and adverse local tissue reactions along with a description of the device used. An additional three papers were located by searching bibliographies of key articles. There were seven case reports, three case series, two case-control studies, and seven analytical studies. The Methodological Index for Non-randomized Studies (MINORS) Scale was used to score case series and case-control studies, which yielded mean scores of 10.3 of 16 and 17.5 of 24, respectively. In general, the case series (three) and case-control (two) studies were of good quality. RESULTS: In lumbar regions, metal-on-polymer devices with mobile-bearing designs consistently generated small and large polymeric wear debris, triggering periprosthetic tissue activation of macrophages and giant cells, respectively. In the cervical regions, metal-on-polymer devices with fixed-bearing designs had similar outcomes. All metal-on-metal constructs tended to generate small metallic wear debris, which typically triggered an adaptive immune response of predominantly activated lymphocytes. There were no retrieval studies on one-piece prostheses. CONCLUSIONS: This review provides evidence that design and biomaterials affect the type of wear and inflammation. However, clinical study design, followup, and analytical techniques differ among investigations, preventing us from drawing firm conclusions about the relationship between implant design and wear performance for both cervical and lumbar total disc replacement.

A systematic review of multivitamin-multimineral use and cardiovascular disease and cancer incidence and total mortality.

Multivitamin-multimineral (MVM) supplements are the most frequently used dietary supplements in the United States, with one third or more of the population using at least one daily. However, the health-related implications of MVM use are unclear. Thus, we systematically reviewed and summarized the prospective studies of MVM supplementation and all-cause and cause-specific mortality, as well as cardiovascular disease (CVD) and cancer incidence, to critically evaluate the current evidence on this topic. We included studies of generally healthy adult populations that evaluated multivitamin (the most commonly used dietary supplement) and/or multimineral supplement use or simultaneous use of 3 or more vitamins and minerals. We did not evaluate individual supplements. A total of 12 cohort studies and 3 primary prevention randomized controlled trials met our inclusion criteria. The majority of the studies were conducted in the United States (n = 11), and the remaining were conducted in European countries (n = 3) and Japan (n = 1). Although between-study methodological variation was present, most relative risks hovered closely around or slightly below the null value. No clear patterns of associations by study country, gender, smoking status, or frequency of use were observed. Based upon the available scientific evidence to date, supplementation with MVMs does not appear to increase all-cause mortality, cancer incidence or mortality, or CVD incidence or mortality and may provide a modest protective benefit.

Air ions and mood outcomes: a review and meta-analysis.

BACKGROUND: Psychological effects of air ions have been reported for more than 80 years in the media and scientific literature. This study summarizes a qualitative literature review and quantitative meta-analysis, where applicable, that examines the potential effects of exposure to negative and positive air ions on psychological measures of mood and emotional state. METHODS: A structured literature review was conducted to identify human experimental studies published through August, 2012. Thirty-three studies (1957-2012) evaluating the effects of air ionization on depression, anxiety, mood states, and subjective feelings of mental well-being in humans were included. Five studies on negative ionization and depression (measured using a structured interview guide) were evaluated by level of exposure intensity (high vs. low) using meta-analysis. RESULTS: Consistent ionization effects were not observed for anxiety, mood, relaxation/sleep, and personal comfort. In contrast, meta-analysis results showed that negative ionization, overall, was significantly associated with lower depression ratings, with a stronger association observed at high levels of negative ion exposure (mean summary effect and 95% confidence interval (CI) following high- and low-density exposure: 14.28 (95% CI: 12.93-15.62) and 7.23 (95% CI: 2.62-11.83), respectively). The response to high-density ionization was observed in patients with seasonal or chronic depression, but an effect of low-density ionization was observed only in patients with seasonal depression. However, no relationship between the duration or frequency of ionization treatment on depression ratings was evident. CONCLUSIONS: No consistent influence of positive or negative air ionization on anxiety, mood, relaxation, sleep, and personal comfort measures was observed. Negative air ionization was associated with lower depression scores particularly at the highest exposure level. Future research is needed to evaluate the biological plausibility of this association.

Air ions and respiratory function outcomes: a comprehensive review.

BACKGROUND: From a mechanistic or physical perspective there is no basis to suspect that electric charges on clusters of air molecules (air ions) would have beneficial or deleterious effects on respiratory function. Yet, there is a large lay and scientific literature spanning 80 years that asserts exposure to air ions affects the respiratory system and has other biological effects. AIMS: This review evaluates the scientific evidence in published human experimental studies regarding the effects of exposure to air ions on respiratory performance and symptoms. METHODS: We identified 23 studies (published 1933-1993) that met our inclusion criteria. Relevant data pertaining to study population characteristics, study design, experimental methods, statistical techniques, and study results were assessed. Where relevant, random effects meta-analysis models were utilized to quantify similar exposure and outcome groupings. RESULTS: The included studies examined the therapeutic benefits of exposure to negative air ions on respiratory outcomes, such as ventilatory function and asthmatic symptoms. Study specific sample sizes ranged between 7 and 23, and studies varied considerably by subject characteristics (e.g., infants with asthma, adults with emphysema), experimental method, outcomes measured (e.g., subjective symptoms, sensitivity, clinical pulmonary function), analytical design, and statistical reporting. CONCLUSIONS: Despite numerous experimental and analytical differences across studies, the literature does not clearly support a beneficial role in exposure to negative air ions and respiratory function or asthmatic symptom alleviation. Further, collectively, the human experimental studies do not indicate a significant detrimental effect of exposure to positive air ions on respiratory measures. Exposure to negative or positive air ions does not appear to play an appreciable role in respiratory function.

A weight-of-evidence review of colorectal cancer in pesticide applicators: the agricultural health study and other epidemiologic studies.

OBJECTIVE: To systematically evaluate epidemiologic studies on pesticides and colon cancer and rectal cancer in agricultural pesticide applicator populations using a transparent "weight-of-evidence" (WOE) methodological approach. METHODS: Twenty-nine (29) publications from the Agricultural Health Study (AHS) and 13 additional epidemiologic studies were identified that reported data for pesticide applicators and/or specific pesticide compounds and colorectal, colon, or rectal cancer. The AHS evaluated pesticide applicators as well as dose-response associations for specific pesticide compounds, whereas the large majority of non-AHS evaluated applicators but did not analyze specific compounds or dose-response trends. This WOE assessment of 153 different pesticide-outcome pairs emphasized several key evidentiary features: existence of statistically significant relative risks, magnitude of observed associations, results from the most reliable exposure assessments, and evidence of convincing dose-response relationships (i.e., those monotonically increasing, with statistically significant trend tests). RESULTS: Occupation as a pesticide applicator or pesticide application as a farming-related function was not associated with increasing the risk of colon or rectal cancer. Deficits of colon or rectal cancer were observed across most studies of pesticide applicators. After applying the WOE methodology to the epidemiologic studies of specific pesticide compounds and colon or rectal cancer, a number of pesticide-outcome pairs were identified and evaluated further based on positive statistical associations. Of these, only two-aldicarb and colon cancer and imazethapyr and proximal colon cancer-appears to warrant further discussion regarding a possible causal relationship, although the epidemiologic data are limited. For the remainder, a lack of a clear dose-response trend, inconsistencies in associations between exposure metrics and comparison groups, imprecise associations, variable participation rates for analyses of specific compounds, and the reliance upon data from one study (the AHS) limit interpretation regarding risk. CONCLUSION: The available epidemiologic evidence does not support a causal relationship between occupation as a pesticide applicator or specific pesticide exposures and colon or rectal cancer.

Occupational trichloroethylene exposure and kidney cancer: a meta-analysis.

BACKGROUND: We conducted a meta-analysis of occupational studies of trichloroethylene-exposed workers to evaluate patterns of associations by study design, exposure assessment methods, and occupational groups. METHODS: Estimates of summary relative risk (RR) were calculated using inverse-variance weighting methods. Cohort studies were classified as group I or group II, depending on quality of the study design and exposure assessment procedures. We conducted sensitivity analyses to examine sources of heterogeneity. RESULTS: Across all studies meeting our inclusion criteria (n = 23), the summary RR was 1.42 (95% confidence interval = 1.17-1.77), with heterogeneity present (test for heterogeneity: P = 0.001). After removal of 3 outlier studies, the summary RR for the remaining studies was 1.24 (1.06-1.45 (test for heterogeneity: P = 0.616)). The summary RR for studies of workers who were identified as more likely exposed to trichloroethylene (group I studies) was 1.34 (1.06-1.68). With outlier studies removed, the group II summary RR estimates for the cohort studies was 0.88 (0.58-1.33) and for the case-control studies was 1.33 (1.02-1.73). The summary RR for studies that used biomarkers to classify exposure (n = 3) was 1.02 (0.59-1.77) and for studies of aerospace/aircraft workers (n = 7) was 1.14 (0.84-1.57). CONCLUSIONS: Positive associations were observed across various study groups. However, considerations of unmeasured potential confounding, lack of quantitative exposure assessment and lack of exposure-response patterns limit epidemiologic insight into the role of trichloroethylene exposure and its potential causal association with kidney cancer.

Partially hydrolyzed 100% whey protein infant formula and reduced risk of atopic dermatitis: a meta-analysis.

OBJECTIVE: A reduced risk of atopic dermatitis (AD) among healthy infants who received 100% whey protein partially hydrolyzed formula (PHF-W) compared with intact protein cow's milk formula (CMF), has been reported in several studies. To validate these observations and estimate the magnitude of this potential association with greater statistical precision, we conducted a meta-analysis of clinical trial and intervention studies. MATERIALS AND METHODS: A total of 18 articles representing 12 independent study populations met our inclusion criteria. RESULTS: A statistically significant 44% (summary relative risk estimate [SRRE] = 0.56, 95% confidence interval 0.40-0.77) reduced risk of atopic manifestations, which included AD, was found among infants receiving PHF-W compared with infants receiving CMF. In a subanalysis of 4 studies that reported results specifically for AD and that were considered of superior methodological quality, the incidence of AD was reduced by 55% (SRRE = 0.45, 95% confidence interval 0.30-0.70). CONCLUSIONS: Regardless of study design, infant population, follow-up time, or study location, individual study findings were consistent because a reduced incidence of AD was reported in all of the reviewed studies. Exclusive breast-feeding should be encouraged as the standard for infant nutrition in the first months of life. For infants who are not exclusively breast-fed, feeding with PHF-W instead of CMF reduces the risk of AD in infants, particularly in infants with a family history of allergy.