Many longitudinal studies are designed like a “snake.” They have a beginning and an end. The study starts at some point in time, data are repeatedly collected over time and data collection ends when the study is completed or there are no more surviving participants.
In contrast, the Maine-Syracuse Longitudinal Study (MSLS) uses a design that was very popular in life-span aging research in 1960 and for many years after. The study design is shown in the figure below. Starting with baseline the original cohort is followed over many years. Outcome measures are obtained at distinct time intervals, but new cohorts of individuals join the study at each specific period. The MSLS was designed to measure outcomes every five years and to add cohorts ever five years.
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