I have incidence-level data for heart disease that includes patient age and region. I calculated disease counts by region and now I want to calculate an age-adjusted rate for each region.
The data spans a decade (2000 - 2010) and this is a disease that affects mostly older people (the youngest patient in the data is 65).
I already have population counts of 65+ year-olds for each region and each year between 2000 and 2010.
What is the proper way to adjust by age? Pick a middle year, say 2006, and use that as the standard population? Or should I calculate a rate for each year and average that somehow?