Immortal time is a span of cohort follow-up during which, because of exposure definition, the
outcome under study could not occur. Bias from immortal time was first identified in the …

OBJECTIVE Time-related biases in observational studies of drug effects have been described
extensively in different therapeutic areas but less so in diabetes. Immortal time bias, time-…

… Samy Suissa, professor of epidemiology and biostatistics1… Suissa S. Effectiveness of
inhaled corticosteroids in chronic obstructive pulmonary disease: immortal time bias in …

Background The long-term natural history of chronic obstructive pulmonary disease (COPD)
in terms of successive severe exacerbations and mortality is unknown. Methods The authors …

Purpose Recent observational studies suggest that various drugs are remarkably effective
at reducing morbidity and mortality. These cohort studies used a flawed approach to design …

Assessing the known or intended effects of a drug using non-experimental epidemiologic
designs is often infeasible because of the absence of accurate data on a major confounder, the …

To determine the frequency of and risk factors fo falls and injurious falls in the noninstitutionalized
elderly, the authors conducted a follow-up study of 409 community-dwelling persons …

Background Although inhaled corticosteroids are effective for the treatment of asthma, it is
uncertain whether their use can prevent death from asthma. Methods We used the …

Background. Morbidity and mortality from asthma appear to be increasing, and it has been
suggested that medications used to treat asthma are contributing to this trend. We …

ContextRecent reports suggest an increasing occurrence and severity of Clostridium difficile–associated
disease. We assessed whether the use of gastric acid–suppressive agents is …