Methods and Applications of Statistics in Clinical Trials, Volume 1: Concepts, Principles, Trials, and Designs

Chapter 40

Longitudinal Data

Hung-I Li

40.1 Definition

Longitudinal data are results from longitudinal studies and essentially consist of outcome measures or responses collected repeatedly over the time for each subject included in the study. This is in contrast to the conventional cross-sectional studies in which subsets of subjects are selected from a population and evaluated all at one point of time. Therefore, longitudinal data link to multiple sets of cross-sectional data over a series of time points.

40.2 Longitudinal Data from Clinical Trials

Longitudinal data could be collected from prospective or retrospective observational studies in epidemiologic or public health research to characterize the disease progression or risk factors for certain epidemics. Penninx et al. [1] reported a community-based study having evaluated 2847 subjects with or without major depression and having evaluated them for 4 years for the diagnosis of cardiac disease and cardiac mortality to assess the association between the cardiac mortality and major depression. Most of the longitudinal data in the clinical research and development settings are collected through prospectively designed longitudinal studies under specific regulatory requirements. For example, a randomized, controlled trial was conducted in 1996–1997 to evaluate the effectiveness of gabapentin for treatment of post-herpetic neuralgia (PHN) as reported by Rowbotham et al. [2]. A total of 229 patients found to have PHN were assigned ...