Wei agreed that confounding by indication
is always a possibility in an observational study such as this.
Confounding by indication
is a critical challenge in evaluating the effectiveness of medical interventions.
However, he suspects that the correlation between antidepressant therapy and suicide in bipolar patients probably was caused by confounding by indication
. "I wouldn't have as a take-home message that SSRI [selective serotonin reuptake inhibitor] antidepressants are bad for you; it's probably rather that these are really bad cases, treatment gets initiated when someone gets worse, and the antidepressants just aren't quick enough to really give an effect.
The researchers caution that this pattern of excess cancer risk may be partly due to confounding by indication
, because the incidence of brain tumors was higher in the cohort than in the general population.
The study also shows that this pattern of excess cancer risk may be partially due to confounding by indication
, as the incidence of brain tumor was higher in the cohort than in the general population.
The baseline characteristics clearly reflect this "confounding by indication
," as patients with modified TEE screening were on average older and had more comorbid conditions than patients without modified TEE.
This confounding by indication
is probably one of the main challenges for the internal validity of observational studies.
Some experts have suggested that the observational studies reporting a link between acetaminophen and asthma exacerbations may have been flawed by "confounding by indication
," because children with asthma have more symptomatic respiratory infections than do those without asthma and use more acetaminophen for fever and malaise.
This selective use of treatment leads to confounding by indication
, a well-recognized limitation of observational studies of the effectiveness of therapeutic interventions.
We restricted our study population to patients eligible for either treatment and we used an intent-to-treat approach combined with multivariate regression to control for confounding by indication
To avoid confounding by indication
, we used the offspring of mothers with one or more dispensed prescriptions of the mecillinam, a penicillin used to treat urinary tract infections, during the 12 weeks before pregnancy as a reference group.
One of the many potential sources of error in observational studies is what is known as "confounding by indication
" which in the present study would denote a failure to adjust for why the participants were taking nutritional supplements.