Question

In the low alcohol group, 174 women developed head and neck cancer in 23,800 person-years of observation, while in the high alcohol group 126 women developed head and neck cancer in 4,200 person-years.

Breast cancer was diagnosed in 710 women with low alcohol intake who contributed 22,100 person-years of observation, while in the high alcohol intake group 290 women developed breast cancer in 3,900 person-years of observation.

Calculate the attributable risk due to high alcohol intake for head and neck cancers and breast cancers in this cohort of women.

Answer 1

For head and neck cancer

The 2x2 contingency table is defined as,

	Head and neck cancer: Yes	Head and neck cancer: No	Total
High alcohol group	a=126	b=4074	a+b=4200
Low alcohol group	c=174	d=23626	c+d=23800
Total	a+c=300	b+d=27700	a+b+c+d=28000

The attributable risk is obtained using the following formula,

where p1 = proportion of head and neck cancer for high alcohol group, and

p2 = proportion of head and neck cancer for low alcohol group

For breast cancer

The 2x2 contingency table is defined as,

	Breast cancer: Yes	Breast cancer: No	Total
High alcohol group	a=290	b=3610	a+b=3900
Low alcohol group	c=710	d=21390	c+d=22100
Total	a+c=300	b+d=27700	a+b+c+d=28000

The attributable risk is obtained using the following formula,

where p1 = proportion of breast cancer for high alcohol group, and

p2 = proportion of breast cancer for low alcohol group