Table 4 Mortality rate ratios from Cox proportional hazards models with penalised spline models for silica and lung cancer: comparison of cohort definitions for the Vermont granite study, 1950–94

Cohort definition	Maximum MRR* (95% CI)	Exposure† at maximum MRR	% Prevalent hires
Hired 1940 or later	2.60 (1.54 to 4.39)	2.25	27.2
Hired 1930 or later	2.45 (1.53 to 3.94)	3.51	36.1
Hired 1920 or later	2.29 (1.62 to 3.23)	4.55	45.7

*Models used age as the timeline and controlled for calendar year and age at hire.
†Cumulative exposure with 15-year lag, in mg-year/m³.