. Author manuscript; available in PMC: 2015 Jan 1.

Published in final edited form as: Cancer Prev Res (Phila). 2013 Nov 26;7(1):33–41. doi: 10.1158/1940-6207.CAPR-13-0224

Table 3.

Hazard ratios and 95% confidence intervals for risk of multiple myeloma according to quantity and duration of regular aspirin use in men and women.

Aspirin use		Men (HPFS)			Women (NHS)		Combined

	Cases	Person-Years	HR (95% CI)^a	Cases	Person-Years	HR (95% CI)^a	HR (95% CI)^b
Cumulative average 325-mg tablets per week
N	72	319,474		193	1,678,032

Non-users	19	73,701	1.00 (ref)	30	369,337	1.00 (ref)	1.00 (ref)

<2	29	133,637	0.79 (0.44–1.42)	75	609,143	0.99 (0.63–1.54)	0.92 (0.66–1.30)

2–<5	21	77,289	0.88 (0.47–1.65)	56	351,847	1.13 (0.71–1.79)	1.04 (0.72–1.50)

≥5	3	34,847	0.28 (0.08–0.95)	32	347,705	0.71 (0.43–1.18)	0.61 (0.39–0.94)

			P-trend=0.11^c			P-trend=0.22^c	P-trend=0.06^c
Continuous duration of regular use, years
N	132	664,264		196	1,731,194

Non-users	52	256,203	1.00 (ref)	30	369,337	1.00 (ref)	1.00 (ref)

≤5	55	269,879	0.77 (0.53–1.14)	94	867,731	0.92 (0.60–1.39)	0.80 (0.61–1.06)

6–10	19	99,134	0.65 (0.38–1.10)	44	293,653	1.32 (0.83–2.11)	0.97 (0.69–1.35)

≥11	6	39,047	0.42 (0.18–0.98)	28	200,472	0.81 (0.48–1.37)	0.63 (0.41–0.95)

			P-trend=0.02^c			P-trend=0.96^c	P-trend=0.17^c

HRs and 95% CIs were computed in Cox proportional hazard models that stratified on age in months and adjusted for current BMI in kg/m².

Cohort-combined Cox proportional hazard models were stratified on age in months and controlled for BMI (kg/m²) and cohort (gender).

For the trend tests, cumulative average tablets/week or continuous duration of regular aspirin use was modeled as an ordinal variable using the mid-point of each category of the respective variable in Cox proportional hazard models stratified by age in months and adjusted for the co-variables indicated.

Abbreviations: HPFS, Health Professionals Follow-up Study; NHS, Nurses’ Health Study; HR, hazard ratio; CI, confidence interval; ref, reference category