Diabetes Bathtub

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People with chronic disease can be pictured as a bath-tub. The inflow from the tap represents the incidence, measured as new cases per year, and the outflow through the drain is due to deaths per year, since we exclude for now the possibility of cure or recovery. The level of water in the bath represents the prevalence, the number of people with the disease. The level of water in the bath will rise until the outflow is greater than the inflow. Note that prevalence is not a rate (a value per unit time). Unfortunately prevalence is sometimes expressed as a rate, but it should be called a ratio (usually percent of population) and rate should be reserved for time rate of change. We don’t use prevalence per year, but refer to incidence per year.

Insight

Fig. 1 - One Stock Diabetes Model and Simulation Run Results [Source]
Fig. 2 - Incidence New Cases per year Converter Values [Source]
Questions & Comments to Geoff McDonnell
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