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Abstract Observational studies are an important category of study designs. To address some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct.
Instead, observational studies may be the next best method to address these types of questions. Well-designed observational studies have been shown to provide results similar to randomized controlled trials, challenging the belief that observational studies are second-rate.
Cohort studies and case-control studies are two primary types of observational studies that aid in evaluating associations between diseases and exposures. In this review article, we describe these study designs, methodological issues, and provide examples from the plastic surgery literature.
However, RCT methodology, which was first developed for drug trials, can be difficult to conduct for surgical investigations. Results from observational studies are often criticized for being vulnerable to influences by unpredictable confounding factors.
However, recent work has challenged this notion, showing comparable results between observational studies and RCTs. Observational studies fall under the category of analytic study designs and are further sub-classified as observational or experimental study designs Figure 1.
The goal of analytic studies is to identify and evaluate causes or risk factors of diseases or health-related events.
The differentiating characteristic between observational and experimental study designs is that in the latter, the presence or absence of undergoing an intervention defines the groups. Case-control and cohort studies offer specific advantages by measuring disease occurrence and its association with an exposure by offering a temporal dimension i.
Cross-sectional studies, also known as prevalence studies, examine the data on disease and exposure at one particular time point Figure 2.
In this review, we will primarily discuss cohort and case-control study designs and related methodologic issues.Clinical Development FTYD (Fingolimod) Study protocol CFTYD Long-term, prospective, non-interventional, multinational, parallel-cohort study monitoring safety in patients with MS.
Clinical Studies and Case Reports. On this site you will find clinical studies with cannabis or single cannabinoids in different diseases and case reports on the use of cannabis by patients.
In current drinkers of alcohol in high-income countries, the threshold for lowest risk of all-cause mortality was about g/week. For cardiovascular disease subtypes other than myocardial infarction, there were no clear risk thresholds below which lower alcohol consumption stopped .
Prospective cohort study. The prospective cohort study is the gold standard in epidemiological study design, and aims to identify unbiased risk estimations of disease for exposures (which can be environmental or genetic) in populations at risk.
A case-cohort study is similar to a nested case-control study in that the cases and non-cases are within a parent cohort; cases and non-cases are identified at time t 1, after baseline.
In a case-cohort study, the cohort members were assessed for risk factros at any time prior to t 1. Perspective. This study evaluated the safety of cannabis use by patients with chronic pain over 1 year.
The study found that there was a higher rate of adverse events among cannabis users compared with controls but not for serious adverse events at an average dose of g herbal cannabis per day.