Singlecohort

Singlecohort, or single-cohort study, is a research design in which a single group of individuals sharing a defining characteristic is followed over time to observe outcomes. The cohort can be defined by disease status, exposure, age, or other attributes, and the study is typically prospective but may be retrospective. A key feature is the absence of a concurrent control group; all analyses describe outcomes within this one group.

Singlecohort designs are common in early-phase clinical research and in natural history studies, especially for rare diseases where enrolling a comparable control population is difficult. They are also used for post-marketing surveillance and long-term follow-up registries. The approach allows detailed, longitudinal data collection on progression, safety signals, or treatment tolerability within a defined population.

Strengths of singlecohort studies include their practicality for studying rare conditions, clearer interpretation of long-term trajectories within the same group, and often simpler logistics compared with randomized or multi-cohort designs. They can generate signals about effectiveness, safety, or natural history that justify further research.

Limitations are substantial. The lack of a control group means causal inferences are limited and results may be confounded by time-related factors or selection bias. Generalizability depends on how representative the cohort is. Statistical analyses must account for confounding, censoring, and missing data, and external comparators or historical controls are sometimes used to contextualize findings.

Common analytic approaches include survival analysis for time-to-event outcomes, and mixed-effects or repeated-measures models for longitudinal measurements. Ethical considerations include informed consent, data privacy, and transparent reporting, particularly when used to inform regulatory or clinical decisions.