To the Editor.—
The report by Evans et al1 is an important study, but there was a glaring omission in their data, namely, the absolute numbers of persons in the different age groups. The percentages of Alzheimer's disease in those 65 through 74 years old, 75 through 84 years old, and older than 85 years are given three times, and there is a large bar graph (Fig 2 of the article). Nowhere could I find the numbers for each group. Given the dramatic increases in percent with each age increment, and since the number of patients in all three groups totaled only 467, a breakdown by group seems important.Perhaps those better versed in biostatistics than I am could take the 95% confidence limits for each group, calculate backward, and get the numbers, but that seems like a lot of work.
Kirkland LR. The Presence of Alzheimer's Disease in a Community Population. JAMA. 1990;263(18):2448. doi:10.1001/jama.1990.03440180045021