excess morality lecture 3- nature of evidence Flashcards
what is epidemiology?
Epidemiology defined by the WHO as ‘the study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems’
what is most physical activity epidemiology?
Most physical activity epidemiology is OBSERVATIONAL and shows ASSOCIATIONS between exposures and disease and further EXPERIMENTAL data is needed to establish CAUSALITY
what is a cross sectional survey?
you have 3 groups of high, medium and low then you compare the prevalence of health related outcomes between groups
what are case control studies?
-when you have healthy controls and people with the health conditions
then you compare the prevalence of exposure variable
-Helpful for understanding risk factors for rare conditions
-Choice of control group is important to reduce risk of bias
what are prospective cohort studies?
-when you have baseline measurements in population free from health related outcomes of interest
-its the same as cross sectional surveys but instead you follow up over several years
-you compare the incidence of health related outcomes between groups during the follow up period
what are confounding factors?
A confounder is a variable that influences both the independent variable (the exposure or treatment) and the dependent variable (the outcome) in a way that can distort the observed relationship between them
what is reverse causality?
Reverse causality occurs when the direction of cause-and-effect is opposite to what is assumed. In other words, instead of X causing Y, Y may actually be causing X. This can lead to incorrect conclusions about the relationship between two variables
what is a randomised controlled trial?
-you have the overall study population then a random allocation to a group
-the 2 groups are assigned a physical activity intervention group and a control group
-then you compare outcomes between randomised groups
what is the criteria for causality with epidemioligical evidence?
-Appropriately sequenced – does the measure of physical activity/fitness/sedentary behaviour precede onset of disease?
-Plausibility – is the association consistent with other knowledge? (mechanisms of action, animal studies)
-Consistency – are findings consistent in different populations?
-Strength – what is the strength of the association between the causal factor and the effect (i.e. what is the relative risk)?
-Dose-response – are increased levels of physical activity or fitness associated with a greater effect?
-Reversibility – is a reduction in activity levels or fitness associated with an increase in disease risk
-Strong study design – are the findings based on strong study designs? (The randomly controlled trial is the ‘gold standard’)
what is Aerobic training, resistance training or both on glycaemic control in type 2 diabetes?
Control group (n = 41) – no exercise
Aerobic training group (n = 72) – 12 kcal/kg/week aerobic exercise over 3 sessions/week
Resistance training group (n = 73) – 2-3 sets of 9 resistance exercises 3 x per week
Combined training group (n = 76) – 12 kcal/kg/week aerobic exercise over 3 sessions/week PLUS 1 set of 9 resistance exercises in each session
SIMILAR EXERCISE TIME FOR THE 3 INTERVENTION GROUPS (~130-150 MIN/WEEK)
what is the Criteria used to evaluate strength of evidence in ACSM position stand on exercise and physical activity for older adults?
Evidence Level A
Overwhelming evidence from randomised controlled trials and/or observational studies, which provides a consistent pattern of findings on the basis of substantial data.
Evidence Level B
Strong evidence from a combination of randomised controlled trials and/or observational studies but with some studies showing results that are inconsistent with the overall conclusion.
Evidence Level C
Generally positive or suggestive evidence from a smaller number of observational studies and/or uncontrolled or nonrandomised trials.
Evidence Level D
Panel consensus judgment that the strength of the evidence is insufficient to place it in categories A through C.
how do we Use RCT data on a risk factor to infer causal link between physical activity and outcome?
increased physical activity = a casual link established from RCT on physical activity and blood pressure = lowered blood pressure = causal link establish from large body of biomedical research = lower risk of CVD
