Cigarette smoking and risk of second primary cancer: a systematic review and meta-analysis

Approximately 5% of the population are living with a diagnosis of cancer. Recent improvements in survival following a diagnosis of cancer have led to an increase in second primary cancers (SPCs) worldwide. Their aetiology remains largely unknown with a large proportion believed to be related to modifiable lifestyle factors. We conducted a systematic review and meta-analysis of published data that evaluated an association between cigarette smoking and risk of SPC. Studies were identified by searching Medline, Web of Science, CINAHL (Cumulative Index to Nursing and Allied Health Literature) and Scopus databases through March 2021 using broad search criteria. A meta-analysis was performed to derive pooled relative risks (RRs) for SPC defined a priori as smoking-related based on current evidence (lung, upper aero-digestive tract, stomach, pancreas, colorectum, liver, kidney, ureter, bladder and acute myeloid leukaemia). Eleven cohort studies and ten case-control studies met the eligibility criteria for review. There was marked heterogeneity in methods used in terms of classification and timing of smoking, confounders adjusted for and duration of follow-up across the studies. Nine cohort and seven case-control studies classified smoking habits prior to diagnosis of first cancer while the remaining studies classified post-first cancer smoking habits. In a meta-analysis using six studies, an increased risk of smoking-related SPC was observed for both former (RR=1.42; 95% confidence interval (CI) 1.20–1.67) and current smoking (RR=2.76; 95% CI 2.29–3.33), compared with never smoking. The pooled RRs changed only slightly when studies which measured post-first cancer smoking were excluded. A two-fold increase in risk was observed for ever smoking compared with never smoking. In conclusion, there was evidence that smoking might increase the risk of SPC in cancer survivors. For better informed cancer survivorship practice guidelines, more studies are needed particularly of post-cancer smoking and for cancers not known to be caused by smoking.     

A systematic review and meta-analysis on the prevalence of infectious diseases of Duck: A world perspective

The Indian poultry industry is one of the fast-growing sectors of which duck farming plays an important role. Duck population in India is 33.51 million that is concentrated towards north-east and southern parts of the country who rears mainly for eggs and meat. Duck diseases are of great concern as they badly affect the financial status of the small, landless farmers. Databases such as Google Scholar, PubMed, J gate were used to search articles between 2000 and 2019 that showed the prevalence of viral, bacterial, and parasitic duck diseases. R open source software was used to derive forest plots by statistical analysis. Pooled prevalence estimates of duck diseases worldwide was found to be 20% (95%-CI:15–26). Also, continent-wise analysis of all duck diseases has revealed highest prevalence in North America, followed by Asia, Africa, Europe,Oceania and South America. This prevalence of data would be helpful to the policymakers to develop appropriate intervention strategies to prevent and control diseases in their respective locations.     

Parity and risk of developing breast cancer according to tumor subtype: A systematic review and meta-analysis

BackgroundClinical breast cancer subtypes are categorized basing on the expression of hormone receptors and overexpression of the human epidermal growth factor receptor 2 (HER2). It is still unclear whether parity impact the risk of different breast cancer subtypes.MethodsWe searched eight mainstream databases for published epidemiologic studies that assessed the relationship between parity and risk of breast cancer subtypes up to January 12, 2021. Parity number were unified into nulliparity and ever parity. The random-effects or fixed-effect models were used to calculate the pooled odds ratios (ORs) and 95% confidence intervals (CIs) among different subtypes. Restricted cubic spline analysis with four knots was applied to determine the relationship of parity number and risk of breast cancer subtypes.ResultsWe pooled sixteen case-control and four cohort studies, and performed an analysis including 7795 luminal A, 3576 luminal B, 1794 HER2-overexpressing, and 5192 triple-negative breast cancer cases among 1135131 participants. The combined ORs for ever parity versus nulliparity indicated a 34% reduction in luminal A risk (OR=0.66, 95% CI: 0.56–0.78), and a 29% reduction in luminal B risk (OR=0.71, 95% CI: 0.63–0.81), there was no significant association in HER2-overexpressing or TNBC risk. In the dose-response analysis, we observed a potentially non-linear and gradually increasing protective relationship between the number of parity and luminal breast cancer risk.ConclusionsThe effect of parity on breast cancer seems to vary among breast tumor subtypes, and it plays a protective role in luminal breast cancer.     

The efficacy and safety of Curcuma longa extract and curcumin supplements on osteoarthritis: a systematic review and meta-analysis

Objective: To assess the efficacy and safety of Curcuma longa extract and curcumin supplements on osteoarthritis (OA).Methods: The databases such as Pubmed and Cochrane Library were searched to collect the article about Curcuma longa extract and curcumin in the treatment of OA. Then, randomized controlled trials (RCTs) were selected and their data were extracted. Finally, the RevMan5.3 was utilized for risk of bias assessment and meta-analysis, the STATA15.0 were utilized for publication bias assessment, and GRADE tool were used for the evidence quality assessment of primary outcomes.Results: A total of 15 RCTs involving 1621 participants were included. (1) Compared with placebo, Curcuma longa extract and curcumin (C.) can decrease the visual analog scale (VAS) and The Western Ontario and McMaster Universities (WOMAC) score-pain, the WOMAC score-function and the WOMAC score-stiffness. In terms of adverse events, Curcuma longa extract and curcumin are comparable with those of placebo. (2) Compared with non-steroidal anti-inflammatory drugs (NSAIDs), Curcuma longa extract and curcumin have similar effects on joint pain, function and stiffness. The incidence of adverse events in Curcuma longa extract and curcumin was lower. (3) Compared with the NSAIDs group, C.+NSAIDs can also decrease the VAS and WOMAC score-pain, the WOMAC score-function and the WOMAC score-stiffness. In terms of adverse events, the addition of Curcuma longa extract and curcumin to NSAIDs did not increase adverse events.Conclusion: Curcuma longa extract and curcumin may be a safer and effective supplement for OA patients. It is recommended to use Curcuma longa extract and curcumin supplement for OA patients for more than 12 weeks.     

Survival pattern of colorectal cancer in Sub-Saharan Africa: A systematic review and meta-analysis

Cancer incidence is relatively low in sub-Saharan Africa (SSA), however, prognosis is expected to be poor in comparison with high-income countries. Comprehensive evidence is limited on the survival pattern of colorectal cancer patients in the region. We conducted a systematic review and meta-analysis to investigate the pattern of colorectal cancer survival in the region and to identify variation across countries and over time. We searched international databases MEDLINE, Scopus, Embase, Web of Science, ProQuest, CINAHL, and Google Scholar to retrieve studies that estimated survival from colorectal cancer in SSA countries from inception to December 31, 2021 without language restriction. Due to between-study heterogeneity, we performed a random-effects meta-analysis to pool survival rates. To identify study-level sources of variation, we performed subgroup analysis and meta-regression. Results are reported in line with the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) 2020 guideline and the protocol was registered in PROSPERO database (CRD42021246935). 23 studies involving 10,031 patients were included in the review, of which, 20 were included in the meta-analysis. The meta-analysis results showed that the pooled 1-, 2-, 3-, 4-, and 5-year survival rates in SSA were 0.74 (95% CI, 0.66–0.81), 0.50 (95% CI, 0.41–0.58), 0.36 (95% CI, 0.27–0.47), 0.31 (95% CI, 0.22–0.42), and 0.28 (95% CI, 0.19–0.38) respectively. Subgroup analyses indicated that the survival rate varied according to year of study, in which those conducted in recent decades showed relatively better survival. The 5-year survival was higher in middle-income SSA countries (0.31; 95%CI: 0.17–0.49) than low-income countries (0.20; 95%CI: 0.11–0.35), however, the difference was not statistically significant. In conclusion, survival from colorectal cancer is low in sub-Saharan Africa compared to other regions. Thus, intervention strategies to improve screening, early diagnosis and treatment of colorectal cancer should be developed and implemented to improve survival in the region.     

The height premium: A systematic review and meta-analysis

The taller people are, the more money they tend to earn. This phenomenon is widely known as the height premium. However, it is not yet known whether the height premium is universal, or whether it varies by context. To that end, a systematic review of the literature was performed. Five databases were searched until August 2020. Ultimately, a list of 42 studies were included in a narrative synthesis, and 17 studies were included in a meta-analysis. Based on the meta-analysis, we found evidence that the height premium varied by context: the height premium was smaller in the U.S. and Australia, and larger in Latin America and Asia. Within geographies, there appeared to be a larger height premium for men than for women. Cultural factors, labor market structures and biology may play a role in determining the strength of the height premium.     

Alcohol drinking and risk of leukemia—A systematic review and meta-analysis of the dose–risk relation

The association between alcohol and leukemia risk has been addressed in several studies in the past two decades, but results have been inconsistent. Therefore, we conducted a systematic review and meta-analysis to quantify the dose–risk relation. Through the literature search up to August 2013, we identified 18 studies, 10 case-control and 8 cohorts, carried out in a total of 7142 leukemia cases. We derived pooled meta-analytic estimates using random-effects models, taking into account the correlation between estimates, and we performed a dose–risk analysis using a class of nonlinear random-effects meta-regression models. Stratified analyses were carried out on leukemia subtypes and groups, in order to identify possible etiologic differences. Compared with nondrinkers, the relative risks (RRs) for all leukemia were 0.94 [95% confidence interval (CI), 0.85–1.03], 0.90 (95% CI, 0.80–1.01) and 0.91 (95% CI, 0.81–1.02) for any, light (≤1 drink/day) and moderate to heavy (>1 drink/day) alcohol drinking, respectively. The summary RRs for any alcohol drinking were 1.47 (95% CI, 0.47–4.62) for acute lymphoblastic leukemia, 0.94 (95% CI 0.77–1.15) for chronic lymphocytic leukemia, 1.02 (95% CI, 0.86–1.21) for acute myeloid leukemia and 0.93 (95% CI 0.75–1.14) for chronic myeloid leukemia. The subgroup analysis on geographical area for all leukemia combined showed RRs of 0.84 (95% CI, 0.76–0.93), 0.92 (95% CI, 0.83–1.01) and 1.32 (95% CI, 1.02–1.70) for studies conducted in America, Europe and Asia, respectively. We did not find an increased risk of leukemia among alcohol drinkers. If any, a modest favorable effect emerged for light alcohol drinking, with a model-based risk reduction of approximately 10% in regular drinkers.     

Early life conditions,reproductive and sexuality-related life history outcomes among human males: A systematic review and meta-analysis

In order to investigate the association between early life conditions and reproductive and sexuality-related life history outcomes among men, we conducted a meta-analysis that compiled the results of 198 articles. A total of 331 effect sizes drawn from 573 samples were included. The meta-analysis revealed that low family socioeconomic status was associated with early sexual debut (r = 0.07), early first birth (r = 0.14), and early marriage (r = 0.03). There was no significant association between family socioeconomic status and pubertal timing or number of sexual partners. Parental absence was associated with early sexual debut (r = ? 0.12), greater number of sexual partners (r = ? 0.19), early first birth (r = ? 0.14), and early marriage (r = ? 0.13). There was no significant association between parental absence and pubertal timing. Small body size before puberty was associated with delayed pubertal timing (r = ? 0.10). There was no significant association between adult body size and number of offspring, and between body size at birth and pubertal timing. Small adult body size, greater number of siblings, and older parents were associated with non-heterosexual orientation (rs = 0.12, 0.03, and 0.03 respectively). Factors such as sampling procedure, data collection method, and age cut-off used to measure family structure change influenced the association between some predictors (e.g., family socioeconomic status) and outcomes (e.g., first birth). The findings are discussed in relation to the utility of life history theory for understanding human male reproductive and sexuality-related outcomes.     

Non-aspirin non-steroidal anti-inflammatory drugs in prevention of colorectal cancer in people aged 40 or older: A systematic review and meta-analysis

There is still insufficient data about the risk-benefit profile about recommending non-aspirin, non-steroidal anti-inflammatory drugs (NA-NSAIDs) for colorectal cancer (CRC) prevention, especially in people aged 40 years or older. This study specifically addressed the association between regular NA-NSAIDs use and CRC risk in the population aged 40 years or older, performing a comprehensive systematic review and meta-analysis of all published studies on this topic until April 2018, by a search of PubMed, Scopus and Web of science databases and clinical trial registries. Two reviewers independently selected studies based on predefined inclusion criteria and assessed study quality using the Newcastle-Otawa scale. The data was combined with the random effects model. Potential heterogeneity was calculated as Q statistic and I² value. A total of 23 studies involving more than 1 million subjects contributed to the analysis. Pooled odds ratio (OR) of NA-NSAIDs effects on CRC risk was 0.74 (0.67-0.81), I² = 75.9%, p < 0.001. Heterogeneity was explained by a number of variables including the quality of the studies. Significant protective effects of NA-NSAIDs use were found for women (risk reduction of 19%), higher doses (risk reduction of 18%), distal colon cancer (risk reduction of 22%) and white people (risk reduction from 31% to 41%). From the results NA-NSAIDs use appears to be CRC chemopreventive for a specific subgroup of the population.     

The concentration of polycyclic aromatic hydrocarbons (PAHs) in mother milk: A global systematic review,meta-analysis and health risk assessment of infants

BackgroundBio-monitoring of polycyclic aromatic hydrocarbons (PAHs) contaminants in mother milk is essential to keep mothers and infants healthy against potential risks. The current study assesses the concentration of PAHs in mother milk through a meta-analytic and systematic review approach.MethodsAll the published studies up to December 2020 regarding the concentrations of various PAHs in mother milk were searched throughout major international databases such as PubMed, Scopus, and Web of Science. Moreover, the possible carcinogenic and mutagenic risks to infants were evaluated based on the BaP (benzo[a]pyrenee) equivalent dose.ResultsAccording to the results of 13 articles included among 936 retrieved studies, the lowest and highest concentration of PAHs was (0.125 ng/g) and (76.36 ng/g) related to benz(a)anthracenem and 1-methylnaphthalene, respectively. The highest (9.830 ng/g) and lowest (0.009 ng/g) concentration of PAHs was related to Mexico and Japan, respectively. Besides, carcinogenetic and mutagenic risk assessment of the PAHs indicated that risk pattern was different across countries. It can be concluded that the consumption of mother milk is safe and does not pose a risk due to the ingestion of PAHs to the health of infant consumers.     

Prevalence of Helicobacter pylori infection in Latin America and the Caribbean populations: A systematic review and meta-analysis

ObjectiveTo describe the prevalence of Helicobacter pylori (H. pylori) infection in Latin Americaand the Caribbean (LAC), through systematic review and meta-analysis by age groups and gender.MethodsSystematic review and meta-analysis of the population-based observational epidemiological studies carried out in LAC, focused on the prevalence of H. pylori and published until March, 2018. The databases utilized in the search were MEDLINE, SCIELO andPUBMED. The prevalence described in the meta-analysis and 95% confidence intervals were estimated by the random effects model, and weighted by the size of the study.ResultsThe 22 selected studies were carried out in 14 countries of LAC, and included 24,178 individuals. The studies were conducted between 1987 and 2012, and all were representative of at least one city. The prevalence of H. pylori infection was 57.57% (CI95%:50.43;64.72) for all ages; in children and adolescents the prevalence was 48.36% (CI95%:38.03;58.70) and in adults 69.26%(CI95%:64.54;76.99). No differences were observed regarding sex.ConclusionPrevalence of H. pylori infection in LAC is high for all age groups. These data reinforce the necessity of actions towards the prevention and treatment of H. pylori infection for all age groups. Treating H pylori infection in young ages probably will reduce gastric cancer incidence in the future.     

Metal concentrations in cerebrospinal fluid,blood, serum,plasma, hair,and nails in amyotrophic lateral sclerosis: A systematic review and meta-analysis

BackgroundAmyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease with progressive muscle wasting, paralysis, and respiratory failure. Whereas approximately 10–15 % of ALS cases are familial, the etiology of the remaining, sporadic ALS cases remains largely unknown. Environmental exposures have been suggested as causative factors for decades, and previous studies have found elevated concentrations of metals in ALS patients.PurposeThis meta-analysis aims to assess metal concentrations in body fluids and tissues of ALS patients.MethodsWe searched the MEDLINE and EMBASE databases on December 7th, 2022 for cross-sectional, case-control, and cohort studies which measure metal concentrations in whole blood, blood plasma, blood serum, cerebrospinal fluid (CSF), urine, erythrocytes, nail, and hair samples of ALS patients. Meta-analysis was then performed when three or more articles existed for a comparison.FindingsTwenty-nine studies measuring 23 metals were included and 13 meta-analyses were performed from 4234 screened entries. The meta-analysis results showed elevated concentrations of lead and selenium. Lead, measured in whole blood in 6 studies, was significantly elevated by 2.88 µg/L (95 % CI: 0.83–4.93, p = 0.006) and lead, measured in CSF in 4 studies, was significantly elevated by 0.21 µg/L (95 % CI: 0.01 – 0.41, p = 0.04) in ALS patients when compared to controls. Selenium, measured in serum/plasma in 4 studies, was significantly elevated by 4.26 µg/L (95% CI: 0.73 – 7.79, p = 0.02) when compared to controls.Analyses of other metal concentrations showed no statistically significant difference between the groups.ConclusionLead has been discussed as a possible causative agent in ALS since 1850. Lead has been found in the spinal cord of ALS patients, and occupational exposure to lead is more common in ALS patients than in controls. Selenium in the form of neurotoxic selenite has been shown to geochemically correlate to ALS occurrence in Italy. Although no causal relationship can be established from the results of this meta-analysis, the findings suggest an involvement of lead and selenium in the pathophysiology of ALS. After a thorough meta-analysis of published studies on metal concentrations in ALS it can only be concluded that lead and selenium are elevated in ALS.     

The effect of silica exposure on the risk of lung cancer: A dose-response meta-analysis

BackgroundThe relationship between silica and the risk of developing lung cancer has been established in previous literature, but how much the level of exposure to silica can increase the risk of lung cancer is a question that has been addressed in this review.MethodsThree electronic databases, including MEDLINE, Scopus, and Web of Science were searched for relevant literature. For the dose-response relationship between exposure to silica and developing lung cancer, we performed a meta-analysis using the random-effects model. For each level of exposure, we calculated the overall risk ratio (RR) with 95% confidence intervals (CI).ResultsNineteen studies were included in the meta-analysis. There was a positive and significant increasing dose-response trend between silica exposure and the risk of developing lung cancer as follows: < 0.50 mg/m³ 1.14 (95% CI: 1.05, 1.23; I² = 79%), 0.50–0.99 mg/m³ 1.34 (95% CI: 1.05, 171; I² = 45%), 1.00–1.99 mg/m³ 1.14 (95% CI: 1.00, 1.30; I² = 70%), 2.00–2.99 mg/m³ 1.47 (95% CI: 1.05, 2.06; I² = 57%), 3.00–3.99 mg/m³ 1.44 (95% CI: 0.99, 2.11; I² = 58%), and ≥ 4.00 mg/m³ 1.64 (95% CI: 1.20, 2.24; I² = 88%). The heterogeneity across studies was mild to moderate.ConclusionsThe presence of a dose-response relationship favors the causal relationship between exposure to silica and developing lung cancer.     

应用益生菌对代谢综合征患者干预效果的系统评价

目的系统评价应用益生菌对代谢综合征患者干预的效果。方法应用计算机检索Web of Science、PubMed、Cochrane Library、EMBASE、中国知网、维普、万方和CBM数据库中应用益生菌干预代谢综合征患者的随机对照试验,对纳入文献采用Cochrane Handbook(5.1.0)进行质量评价,采用RevMan 5.3软件进行Meta分析。结果共纳入9项研究。评价结果为口服益生菌可以降低代谢综合征患者腰围[MD=-2.39,95%CI(-4.58,-0.19),P=0.03]和低密度脂蛋白水平[SMD=-0.41,95%CI(-0.78,-0.04),P=0.03],在一定程度上改善胰岛素抵抗水平,但对空腹血糖水平[SMD=-0.03,95%CI(-0.31,0.24),P=0.83]没有影响。结论应用益生菌干预代谢综合征患者可产生减肥效果,同时在一定程度上改善代谢综合征患者糖代谢紊乱状态,调节脂质代谢水平。但未来仍需要本土化、大样本、高质量的研究进一步探索益生菌干预代谢综合征患者的效果及最有效方案。     

Genetic polymorphism of MMP family and coronary disease susceptibility: a meta-analysis

The issue that genetic polymorphism of matrix metalloproteinase (MMP) family is in association with coronary disease is controversial. So we did a meta-analysis to clarify it clearly. We made a literature search of PubMed, the Web of Science, and Cochrane Collaboration's database to identify eligible reports. The methodological quality of each included studies was assessed. We calculated the pooled ORs with their 95%CI for each genetic polymorphism in STATA 11 software. Separate analysis was performed to address the consistency of results across the subgroup with different continents. A total of 39 studies were included, with a sample of 42269 individuals. This meta-analysis provided evidence that genetic polymorphism of MMP1-1607 1G/2G, MMP3-Gly45lys, MMP3-376 G/C, MMP3-1171 5A/6A, MMP9-1562 C/T and MMP9-R279Q have a small to medium effect on incidence of coronary disease. There was no evidence that MMP1-519 A/G, MMP1-340 T/C and MMP2-1306 C/T polymorphism could increase risk of coronary disease. Results from subgroup analysis supported a relation between MMP3-1711 5A allele, MMP9-1562 C allele and coronary disease especially in Asian population. The results provide moderate association between the six common genetic polymorphism of matrix metalloproteinase family and coronary disease. However, the challenge for researcher is identifying separate effect on different races.     

Acute liver failure: A systematic review and network meta-analysis of optimal type of stem cells in animal models

BACKGROUND The therapeutic effects of various stem cells in acute liver failure(ALF) have been demonstrated in preclinical studies.However,the specific type of stem cells with the highest therapeutic potential has not been determined.AIM To validate the efficacy of stem cells in ALF model and to identify the most promising stem cells.METHODS A search was conducted on the PubMed,Web of Science,Embase,Scopus,and Cochrane databases from inception to May 3,2022,and updated on November 16,2022 to ide...     

Statin use and survival in colorectal cancer: Results from a population-based cohort study and an updated systematic review and meta-analysis

BackgroundThe aim of this study was to investigate the association between statin use and survival in a population-based colorectal cancer (CRC) cohort and perform an updated meta-analysis to quantify the magnitude of any association.MethodsA cohort of 8391 patients with newly diagnosed Dukes’ A-C CRC (2009–2012) was identified from the Scottish Cancer Registry. This cohort was linked to the Prescribing Information System and the National Records of Scotland Death Records (until January 2015) to identify 1064 colorectal cancer-specific deaths. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for cancer-specific mortality by statin use were calculated using time dependent Cox regression models. The systematic review included relevant studies published before January 2016. Meta-analysis techniques were used to derive combined HRs for associations between statin use and cancer-specific and overall mortality.ResultsIn the Scottish cohort, statin use before diagnosis (HR = 0.84, 95% CI 0.75–0.94), but not after (HR = 0.90, 95% CI 0.77–1.05), was associated with significantly improved cancer-specific mortality. The systematic review identified 15 relevant studies. In the meta-analysis, there was consistent (I² = 0%,heterogeneity P = 0.57) evidence of a reduction in cancer-specific mortality with statin use before diagnosis in 6 studies (n = 86,622, pooled HR = 0.82, 95% CI 0.79–0.86) but this association was less apparent and more heterogeneous (I² = 67%,heterogeneity P = 0.03) with statin use after diagnosis in 4 studies (n = 19,152, pooled HR = 0.84, 95% CI 0.68–1.04).ConclusionIn a Scottish CRC cohort and updated meta-analysis there was some evidence that statin use was associated with improved survival. However, these associations were weak in magnitude and, particularly for post-diagnosis use, varied markedly between studies.     

Derivation and validation of clinical phenotypes for COPD: a systematic review

Background

The traditional classification of COPD, which relies solely on spirometry, fails to account for the complexity and heterogeneity of the disease. Phenotyping is a method that attempts to derive a single or combination of disease attributes that are associated with clinically meaningful outcomes. Deriving phenotypes entails the use of cluster analyses, and helps individualize patient management by identifying groups of individuals with similar characteristics. We aimed to systematically review the literature for studies that had derived such phenotypes using unsupervised methods.

Methods

Two independent reviewers systematically searched multiple databases for studies that performed validated statistical analyses, free of definitive pre-determined hypotheses, to derive phenotypes among patients with COPD. Data were extracted independently.

Results

9156 citations were retrieved, of which, 8 studies were included. The number of subjects ranged from 213 to 1543. Most studies appeared to be biased: patients were more likely males, with severe disease, and recruited in tertiary care settings. Statistical methods used to derive phenotypes varied by study. The number of phenotypes identified ranged from 2 to 5. Two phenotypes, with poor longitudinal health outcomes, were common across multiple studies: young patients with severe respiratory disease, few cardiovascular co-morbidities, poor nutritional status and poor health status, and a phenotype of older patients with moderate respiratory disease, obesity, cardiovascular and metabolic co-morbidities.

Conclusions

The recognition that two phenotypes of COPD were often reported may have clinical implications for altering the course of the disease. This review also provided important information on limitations of phenotype studies in COPD and the need for improvement in future studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0208-4) contains supplementary material, which is available to authorized users.