Statistical Analyses
We identified death within the first year following the fracture for each woman within a
matched case and control quintuplet (1 case plus 4 controls), based on the date of fracture
for the case. When no death occurred for any woman within the quintuplet, we also
evaluated mortality from one to five years; quintuplets without a death within 5 years postcase
fracture were further evaluated for mortality from five to 10 years of the case fracture
date. Thus, in the 5- to 10-year period, all five women in the quintuplet had to survive at
least 5 years.