Table 3.

Relative risk of incident kidney stones in men < 60 years of age (HPFS) and women (NHS I and NHS II) by quintile of dairy calcium intake.

	Quintile 1	Quintile 2	Quintile 3	Quintile 4	Quintile 5	P for trend
HPFS
Quintile median* (mg/day)	151	272	385	528	839
Cases	252	261	214	216	190
Person-years	61,397	64,447	62,981	62,671	60,048
Age-adjusted RR (95% CI)	1.0	0.98 (0.82–1.16)	0.82 (0.69–0.99)	0.83 (0.70–1.00)	0.77 (0.64–0.93)	0.002
Multivariate RR+ (95% CI)	1.0	0.95 (0.79–1.13)	0.79 (0.66–0.95)	0.80 (0.67–0.97)	0.77 (0.63–0.95)	0.01
NHS I
Quintile median* (mg/day)	143	266	377	523	816
Cases	400	411	351	363	281
Person-years	284,583	287,508	289,352	289,877	290,242
Age-adjusted RR (95% CI)	1.0	1.01 (0.88–1.16)	0.86 (0.75–1.00)	0.89 (0.77–1.03)	0.70 (0.60–0.82)	<0.001
Multivariate RR+ (95% CI)	1.0	1.02 (0.89–1.18)	0.91 (0.78–1.05)	0.97 (0.84–1.13)	0.83 (0.69–0.99)	0.05
NHS II
Quintile median* (mg/day)	181	319	446	615	937
Cases	559	500	443	444	385
Person-years	254,554	256,792	258,225	259,369	260,835
Age-adjusted RR (95% CI)	1.0	0.89 (0.79–1.01)	0.79 (0.70–0.89)	0.79 (0.69–0.89)	0.68 (0.60–0.77)	<0.001
Multivariate RR+ (95% CI)	1.0	0.91 (0.81–1.03)	0.83 (0.73–0.95)	0.85 (0.74–0.97)	0.76 (0.65–0.88)	0.001

^*For illustrative purposes, dairy calcium values were derived from responses to the 1994 (men and older women) and 1995 (younger women) dietary questionnaires. Updated period-specific values were used in the prospective analyses.

+Results are adjusted for age, BMI (six categories), history of diabetes, history of hypertension, use of thiazide diuretics (yes or no), family history of kidney stones (yes or no; HPFS and NHS II), fluid intake (in quintiles), alcohol use (seven categories), calcium supplement use (four categories), and intakes of non-dairy dietary calcium, animal protein, potassium, sodium, vitamin C, sodium, oxalate, magnesium, and caffeine (all in quintiles).

HPFS: Health Professionals Follow-up Study

NHS: Nurses’ Health Study