Table 1. Calculation of the standardized incidence and mortality ratios based on a cohort study on the association of hormone replacement therapy (HRT) and breast cancer (13).

a) Expected incidence in exposed study population
Age group	Number of exposed persons in each age group in the cohort (fictive) A	Breast cancer incidence in each age group per 100 000 (general German population* [19]) B-	Expected number of exposed cases of breast cancer in exposed members of each age group per year in the cohort C = A x B	Expected number of exposed cases of breast cancer in exposed members of each age group in 2.6 years in the cohort D = C x 2.6
50–54	181 736	221.1	401.8	1 044.7
55–59	138 119	286.9	396.3	1 030.4
60–64	116 311	299.1	347.9	904.5
Total	436 166	–	1146.0	2 979.6
b) Expected mortality in exposed study population
Age group	Number of exposed persons in each age group in the cohort (fictive) A	Breast cancer mortality in each age group per 100 000 (general German population* [19]) B	Expected number of deaths from breast cancer in exposed members of each age group per year in the cohort C = A x B	Expected number of deaths from breast cancer in exposed members of each age group in 2.6 years in the cohort D = C x 2.6
50–54	181 736	39.7	72.1	187.6
55–59	138 119	58.3	80.5	209.4
60–64	116 311	75.8	88.2	229.2
Total	436 166	–	240.8	626.2

^*taken as approximation for breast cancer incidence and mortality in Great Britain