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. Author manuscript; available in PMC: 2014 Apr 27.
Published in final edited form as: JAMA Neurol. 2014 Mar;71(3):315–323. doi: 10.1001/jamaneurol.2013.5570

Table 9.

Calculation of Standardized Incidence Ratio in the NIA-LOAD/NCRAD Families Using Population-Based Rates Published in the Mayo Clinic Studya

Age Group, y Mayo Clinic Rochester Ratesb Person-years at Risk in NIA-LOAD/NCRAD Study No. of Incident Cases
Expected Observed
65–74 0.005 1262 6.4 36
75–84 0.017 894 15.6 58
≥85 0.041 302 12.4 24
All 34.4 118

Abbreviation: NIA-LOAD/NCRAD; National Institute on Aging Genetics Initiative for Late-Onset Alzheimer Disease/National Cell Repository for Alzheimer Disease.

a

The overall standardized incidence ratio for the NIA-LOAD/NCRAD families compared with the Mayo Clinic Rochester population-based rate was 3.44 (95% CI, 2.82–4.06), indicating that the incidence was at least 3-fold higher.

b

Data are found in Knopman et al.15