The Basics of Epidemiology

2021 ◽  
Author(s):  
Min-Shi Lee ◽  
Li-Min Huang
Keyword(s):  
Cohort Studies ◽  
Prospective Cohort ◽  
Observational Studies ◽  
Vaccine Development ◽  
Epidemiological Studies ◽  
Case Definition ◽  
Double Blind ◽  
Immunization Policy ◽  
Disease Reduction ◽  
To Receive

Epidemiology contributes to vaccine development and delivery by estimating disease burdens, identifying target populations for immunization, designing clinical trials to show vaccine-induced benefits and risks, and for formulating immunization policy. To estimate disease burden, a case definition is needed first. This may have several sets of criteria, depending on how definite the diagnosis is to be. Epidemiological studies to determine time, place, and person are referred to as descriptive epidemiology. Epidemiological studies to determine causes and effects are referred to as analytical epidemiology. Epidemiological studies may potentially be biased (systemic errors). Bias must be distinguished from confounding (interfering factors that are linked with both, exposure and outcome). Vaccine efficacy studies assess causality between vaccination and disease reduction in a prospective cohort design. Participants are assigned to receive vaccine or placebo usually in a double-blind, randomized fashion and efficacy is calculated from incidence reduction during the study period. Impact studies are observational studies and encompass e.g., describing disease reduction in a population over time after introduction of a vaccine, as well as cohort studies where vaccine effectiveness is calculated from cohorts in which vaccine administration is only observed. Observational studies are timesaving and less costly compared with prospective cohort studies. However, they are prone to various types of bias, e.g. recall bias if exposure status and outcome status are based on the participant's memory.

scholarly journals Associations of Whole Grain and Refined Grain Consumption With Metabolic Syndrome. A Meta-Analysis of Observational Studies

2021 ◽  
Vol 8 ◽  
Author(s):  
Hongbin Guo ◽  
Jun Ding ◽  
Jieyu Liang ◽  
Yi Zhang
Keyword(s):  
Metabolic Syndrome ◽  
Cohort Studies ◽  
Prospective Cohort ◽  
Observational Studies ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Whole Grain ◽  
Cross Sectional ◽  
Prospective Cohort Studies ◽  
Embase Database

Background: The associations of whole grain and refined grain consumption with metabolic syndrome (MetS) has been evaluated in several epidemiological studies with conflicting results. This meta-analysis was therefore employed to further investigate the above associations.Method: We searched the PubMed, Web of Science and Embase database until March 2021 (without restriction for inclusion time), for observational studies on the associations of whole grain and refined grain consumption with MetS. The pooled relative risk (RR) of MetS for the highest vs. lowest category of whole grain and refined grain consumption, as well as their corresponding 95% confidence interval (CI) were calculated.Results: A total of 14 observational studies, which involved seven cross-sectional and seven prospective cohort studies, were identified. Specifically, nine studies were related to whole grain consumption, and the overall multi-variable adjusted RR demonstrated that the whole grain consumption was inversely associated with MetS (RR = 0.80, 95%CI: 0.67–0.97; P = 0.021). With regard to refined grain consumption, 13 studies were included. The overall multi-variable adjusted RR indicated that refined grain consumption was positively associated with MetS (RR = 1.37, 95%CI: 1.02–1.84; P = 0.036).Conclusions: The existing evidence suggests that whole grain consumption is negatively associated with MetS, whereas refined grain consumption is positively associated with MetS. Our result might be helpful to better consider the diet effect on MetS. However, more well-designed prospective cohort studies are needed to elaborate the concerned issues further.

scholarly journals Customary physical activity and odds of depression: a systematic review and meta-analysis of 111 prospective cohort studies

2021 ◽  
pp. bjsports-2020-103140
Author(s):  
Rodney K Dishman ◽  
Cillian P McDowell ◽  
Matthew Payton Herring
Keyword(s):  
Physical Activity ◽  
Systematic Review ◽  
Depressive Symptoms ◽  
Cohort Studies ◽  
Prospective Cohort ◽  
Observational Studies ◽  
Meta Analysis ◽  
Vigorous Physical Activity ◽  
Prospective Cohort Studies ◽  
Over Time

ObjectiveTo explore whether physical activity is inversely associated with the onset of depression, we quantified the cumulative association of customary physical activity with incident depression and with an increase in subclinical depressive symptoms over time as reported from prospective observational studies.DesignSystematic review and meta-analysis.Data sourcesMEDLINE, PsycINFO, PsycARTICLES and CINAHL Complete databases, supplemented by Google Scholar.Eligibility criteriaProspective cohort studies in adults, published prior to January 2020, reporting associations between physical activity and depression.Study appraisal and synthesisMultilevel random-effects meta-analysis was performed adjusting for study and cohort or region. Mixed-model meta-regression of putative modifiers.ResultsSearches yielded 111 reports including over 3 million adults sampled from 11 nations in five continents. Odds of incident cases of depression or an increase in subclinical depressive symptoms were reduced after exposure to physical activity (OR, 95% CI) in crude (0.69, 0.63 to 0.75; I2=93.7) and adjusted (0.79, 0.75 to 0.82; I2=87.6) analyses. Results were materially the same for incident depression and subclinical symptoms. Odds were lower after moderate or vigorous physical activity that met public health guidelines than after light physical activity. These odds were also lower when exposure to physical activity increased over time during a study period compared with the odds when physical activity was captured as a single baseline measure of exposure.ConclusionCustomary and increasing levels of moderate-to-vigorous physical activity in observational studies are inversely associated with incident depression and the onset of subclinical depressive symptoms among adults regardless of global region, gender, age or follow-up period.

scholarly journals Dietary patterns and CVD: a systematic review and meta-analysis of observational studies

2015 ◽  
Vol 114 (9) ◽  
pp. 1341-1359 ◽  
Author(s):  
Míriam Rodríguez-Monforte ◽  
Gemma Flores-Mateo ◽  
Emília Sánchez
Keyword(s):  
Cohort Studies ◽  
Dietary Patterns ◽  
Observational Studies ◽  
Protective Factor ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Case Control ◽  
Case Control Studies ◽  
Chd Risk ◽  
Control Comparison

AbstractEpidemiological studies show that diet is linked to the risk of developing CVD. The objective of this meta-analysis was to estimate the association between empirically derived dietary patterns and CVD. PubMed was searched for observational studies of data-driven dietary patterns that reported outcomes of cardiovascular events. The association between dietary patterns and CVD was estimated using a random-effects meta-analysis with 95 % CI. Totally, twenty-two observational studies met the inclusion criteria. The pooled relative risk (RR) for CVD, CHD and stroke in a comparison of the highest to the lowest category of prudent/healthy dietary patterns in cohort studies was 0·69 (95 % CI 0·60, 0·78; I2=0 %), 0·83 (95 % CI 0·75, 0·92; I2=44·6 %) and 0·86 (95 % CI 0·74, 1·01; I2=59·5 %), respectively. The pooled RR of CHD in a case–control comparison of the highest to the lowest category of prudent/healthy dietary patterns was 0·71 (95 % CI 0·63, 0·80; I2=0 %). The pooled RR for CVD, CHD and stroke in a comparison of the highest to the lowest category of western dietary patterns in cohort studies was 1·14 (95 % CI 0·92, 1·42; I2=56·9 %), 1·03 (95 % CI 0·90, 1·17; I2=59·4 %) and 1·05 (95 % CI 0·91, 1·22; I2=27·6 %), respectively; in case–control studies, there was evidence of increased CHD risk. Our results support the evidence of the prudent/healthy pattern as a protective factor for CVD.

scholarly journals Egg Consumption and Risk of Upper Aero-Digestive Tract Cancers: A Systematic Review and Meta-Analysis of Observational Studies

2019 ◽  
Vol 10 (4) ◽  
pp. 660-672 ◽  
Author(s):  
Azadeh Aminianfar ◽  
Roohallah Fallah-Moshkani ◽  
Asma Salari-Moghaddam ◽  
Parvane Saneei ◽  
Bagher Larijani ◽  
...  
Keyword(s):  
Systematic Review ◽  
Esophageal Cancer ◽  
Cohort Studies ◽  
Prospective Cohort ◽  
Observational Studies ◽  
Meta Analysis ◽  
Case Control ◽  
Egg Consumption ◽  
Prospective Cohort Studies ◽  
Increased Risk

ABSTRACT Limited data are available that summarize the relation between egg intake and the risk of upper aero-digestive tract (UADT) cancers. This systematic review and meta-analysis was conducted to investigate the association between egg intake and the risk of UADT cancers. Medline/PubMed, ISI web of knowledge, EMBASE, Scopus, and Google Scholar were searched using relevant keywords. Observational studies conducted on humans investigating the association between egg consumption and the risk of UADT cancers were included. Overall, 38 studies with a total of 164,241 subjects (27, 025 cases) were included. Based on 40 effect sizes from 32 case-control studies, we found a 42% increased risk of UADT cancers among those with the highest egg consumption (ranging from ≥1 meal/d to ≥1 time/mo among studies) compared to those with the lowest intake (ranging from 0–20 g/d to never consumed among studies) (overall OR: 1.42; 95% CI: 1.19, 1.68; P < 0.001). However, this association was only evident in hospital-based case-control (HCC) studies (OR = 1.50; 95% CI: 1.34, 1.68; P < 0.001 for ‘oropharyngeal and laryngeal cancer’ and OR: 1.27; 95% CI: 1.08, 1.50; P = 0.004 for esophageal cancer) and not in population-based case-control (PCC) studies (OR = 1.25; 95% CI: 0.59, 2.67; P = 0.56 for ‘oropharyngeal and laryngeal cancer’ and OR: 1.29; 95% CI: 0.92, 1.81; P = 0.13 for esophageal cancer). In addition, the association was not significant in prospective cohort studies (overall OR: 0.86; 95% CI: 0.71, 1.04; P = 0.11). Considering individual cancers, a positive association was observed between the highest egg consumption, compared with the lowest, and risk of oropharyngeal (OR: 1.88; 95% CI: 1.61, 2.20; P < 0.001), laryngeal (OR: 1.83; 95% CI: 1.45, 2.32; P < 0.001), oral & pharyngeal & laryngeal (OR: 1.37; 95% CI: 1.12, 1.67; P < 0.001), and esophageal cancers (OR: 1.28; 95% CI: 1.10,1.48; P = 0.001). We also found an inverse association between egg intake and the risk of oral cancer (OR: 0.78; 95% CI: 0.62, 0.99; P = 0.04). In conclusion, high egg consumption (ranging from ≥1 meal/d to ≥1 time/mo among studies) was associated with increased risk of UADT cancers only in HCC studies but not in PCC or prospective cohort studies. PROSPERO registration number: CRD42018102619.

scholarly journals Design and implementation of observational studies to measure disease burden with a focus on stroke

2017 ◽  
Vol 13 (2) ◽  
pp. 157-165
Author(s):  
George Howard ◽  
Virginia J Howard
Keyword(s):  
Cohort Studies ◽  
Study Design ◽  
Observational Studies ◽  
Disease Burden ◽  
Epidemiological Studies ◽  
Cross Sectional ◽  
Surveillance Studies ◽  
Design And Implementation ◽  
Design Considerations ◽  
Cross Sectional Studies

Observational epidemiological studies have the dual goals of measuring disease burden and assessing the association between exposures and outcomes. This report focuses on the first of these goals and provides an overview of design considerations of commonly used approaches, specifically community surveillance studies, cross-sectional studies, and longitudinal cohort studies. Each of these designs has strengths and weaknesses, with no study design being superior in all cases. Rather, these designs are complementary to achieve a better understanding of the burden of stroke.

scholarly journals Dairy consumption and CVD: a systematic review and meta-analysis

2016 ◽  
Vol 115 (4) ◽  
pp. 737-750 ◽  
Author(s):  
Dominik D. Alexander ◽  
Lauren C. Bylsma ◽  
Ashley J. Vargas ◽  
Sarah S. Cohen ◽  
Abigail Doucette ◽  
...  
Keyword(s):  
Cohort Studies ◽  
Dose Response ◽  
Prospective Cohort ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Sensitivity Analyses ◽  
Dairy Intake ◽  
Prospective Cohort Studies ◽  
Dairy Consumption ◽  
Risk Estimates

AbstractInverse 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.

scholarly journals Fish Consumption and the Risk of Chronic Disease: An Umbrella Review of Meta-Analyses of Prospective Cohort Studies

2020 ◽  
Vol 11 (5) ◽  
pp. 1123-1133 ◽  
Author(s):  
Ahmad Jayedi ◽  
Sakineh Shab-Bidar
Keyword(s):  
Chronic Disease ◽  
Cohort Studies ◽  
Fish Consumption ◽  
Prospective Cohort ◽  
Lower Risk ◽  
Observational Studies ◽  
Prospective Cohort Studies ◽  
Moderate Quality ◽  
Meta Analyses

ABSTRACT We aimed to present a comprehensive review of published meta-analyses of prospective cohort studies on the association of fish consumption and the risk of chronic disease. A systematic search was undertaken in Pubmed and Scopus to October 2019 to find meta-analyses of observational studies evaluating the association of fish consumption and the risk of chronic disease. Retrospective and cross-sectional studies and studies with unadjusted risk estimates were excluded. The summary relative risk (SRR) for each meta-analysis was recalculated by using a random-effects model. The methodological quality of included meta-analyses and the quality of the evidence were assessed by the AMSTAR and NutriGrade tools, respectively. A total of 34 meta-analyses of prospective observational studies, reporting SRRs for 40 different outcomes obtained from 298 primary prospective cohort studies, were included. Moderate-quality evidence suggested that each 100-g/d increment in fish consumption was associated with a lower risk of all-cause mortality (SRR: 0.92; 95% CI: 0.87, 0.97), cardiovascular mortality (SRR: 0.75; 95% CI: 0.65, 0.87), coronary heart disease (SRR: 0.88; 95% CI: 0.79, 0.99), myocardial infarction (SRR: 0.75; 95% CI: 0.65, 0.93), stroke (SRR: 0.86; 95% CI: 0.75, 0.99), heart failure (SRR: 0.80; 95% CI: 0.67, 0.95), depression (SRR: 0.88; 95% CI: 0.79, 0.98), and liver cancer (SRR: 0.65; 95% CI: 0.48, 0.87). For cancers of most sites, there was no significant association and the quality of the evidence was rated low and very low. In conclusion, evidence of moderate quality suggests that fish consumption is associated with a lower risk of cardiovascular disease, depression, and mortality and, therefore, can be considered as a healthy animal-based dietary source of protein. Further research is needed for outcomes for which the quality of the evidence was rated low and very low, considering types of fish consumed, different methods of cooking fish, and all potential confounding variables.

Consumption of Artificially-sweetened Soft Drinks and Risk of Gastrointestinal Cancer: A Meta-analysis of Observational Studies

2021 ◽  
pp. 1-50
Author(s):  
Alfred Jatho ◽  
Jansen Marcos Cambia ◽  
Seung-Kwon Myung ◽  
Keyword(s):  
Cohort Studies ◽  
Observational Studies ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Case Control ◽  
Soft Drinks ◽  
Case Control Studies ◽  
Gi Cancer ◽  
Increased Risk ◽  
Meta Analyses

Abstract Objective: There remain inconclusive findings from previous observational epidemiological studies on whether consumption of artificially-sweetened soft drinks (ASSDs) increases the risk of gastrointestinal (GI) cancer. We investigated the associations between the consumption of ASSDs and the risk of GI cancer using a meta-analysis. Design: Systematic review and meta-analysis. Setting: PubMed and EMBASE were searched using keywords until May 2020 to identify observational epidemiological studies on the association between the consumption of ASSDs and the risk of GI cancer. Subjects: Twenty-one case-control studies and 17 cohort studies with 12,397 cancer cases and 2,474,452 controls. Results: In the random-effects meta-analysis of all the studies, consumption of ASSDs was not significantly associated with the risk of overall GI cancer (odds ratio (OR)/relative risk (RR), 1.02; 95% CI, 0.92-1.14). There was no significant association between the consumption of ASSDs and the risk of overall GI cancer in the subgroup meta-analyses by study design (case-control studies: OR, 0.95; 95% CI, 0.82-1.11; cohort studies: RR, 1.14; 95% CI, 0.97-1.33). In the subgroup meta-analysis by type of cancer, consumption of ASSDs was significantly associated with the increased risk of liver cancer (OR/RR, 1.28; 95% CI,1.03-1.58). Conclusions: The current meta-analysis of observational epidemiological studies suggests that overall, there is no significant association between the consumption of ASSDs and the risk of GI cancer.

Fruit and vegetable intake and liver cancer risk: a meta-analysis of prospective cohort studies

2019 ◽  
Vol 10 (8) ◽  
pp. 4478-4485 ◽  
Author(s):  
Xiao-fei Guo ◽  
Xian-feng Shao ◽  
Jiao-mei Li ◽  
Shan Li ◽  
Ke-lei Li ◽  
...  
Keyword(s):  
Liver Cancer ◽  
Cancer Risk ◽  
Cohort Studies ◽  
Prospective Cohort ◽  
Vegetable Intake ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Fruit And Vegetable Intake ◽  
Fruit Intake ◽  
Prospective Cohort Studies

The associations of vegetable and fruit intake with liver cancer risk have been inconsistent based on epidemiological studies.

Abstract P320: Dairy Consumption and Risk of Stroke: A Systematic Review and Dose-response Meta-analysis of Prospective Cohort Studies

Circulation ◽  
2016 ◽  
Vol 133 (suppl_1) ◽  
Author(s):  
Janette de Goede ◽  
Johanna M. Geleijnse ◽  
An Pan ◽  
Lieke Gijsbers ◽  
Sabita Soedamah-Muthu
Keyword(s):  
Systematic Review ◽  
Cohort Studies ◽  
Dose Response ◽  
Prospective Cohort ◽  
Stroke Risk ◽  
Meta Analysis ◽  
Epidemiological Studies ◽  
Prospective Cohort Studies ◽  
Asian Populations ◽  
Dairy Consumption

Introduction: A higher milk consumption may be associated with a lower stroke risk. We conducted a comprehensive systematic review and dose-response meta-analysis of milk and other dairy products with stroke risk. Hypothesis: We assessed the hypothesis that milk and possibly other types of dairy consumption were inversely associated with stroke risk. Methods: Through a systematic literature search prospective cohort studies of dairy foods and incident stroke in stroke-free adults were identified. Random-effects meta-analyses with summarized dose-response data were performed taking into account sources of heterogeneity and spline models were used to systematically investigate nonlinearity of the associations. Results: We included 17 studies with 10-26 years of follow-up that included 675,389 individuals and 28,912 stroke events. An increment of 200 gram of daily milk intake was associated with a 7% lower risk of stroke (RR 0.93; 95% CI 0.88-0.97; P=0.003; I2=85%). RRs were 0.82 (95% CI 0.75-0.90) in East Asian and 0.98 (95% CI 0.96-1.01) in Western countries (median intakes 38 and 266 g/d respectively) with moderate heterogeneity within the continents. Cheese intake was marginally inversely associated with stroke risk (RR 0.97; 95% CI 0.94-1.01 per 40 g/d). Risk reductions were maximal around 125 g/d for milk and from 25 g/d onwards for cheese. Based on a limited number of studies, low-fat milk was inversely and high-fat milk directly associated with stroke risk. No associations were found for yogurt, butter or total dairy. Conclusions: Milk and cheese consumption were inversely associated with stroke risk. Future epidemiological studies should provide more details about dairy types, including fat content. In addition, the role of dairy in Asian populations deserves further attention.

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