Table 3.

Relative risk of incident symptomatic kidney stones according to gallstone history in older women (NHS I), younger women (NHS II), and men (HPFS).^*

	Person-years	Incident kidney stones	Age-adjusted relative risk	Multivariate relative risk**
NHS I
Gallstone history
No	1,512,008	1195	1.00 (reference)	1.00 (reference)
Yes	226,580	268	1.50 (1.31 to 1.71)	1.26 (1.09 to 1.44)
NHS II
Gallstone history
No	1,061,940	1700	1.00 (reference)	1.00 (reference)
Yes	92,926	241	1.66 (1.45 to 1.90)	1.32 (1.14 to 1.52)
HPFS
Gallstone history
No	557,184	1585	1.00 (reference)	1.00 (reference)
Yes	31,170	97	1.37 (1.11 to 1.68)	1.28 (1.03 to 1.57)

Note: NHS = Nurses’ Health Study. HPFS = Health Professionals Follow-up Study.

^*Participants who reported kidney stones on the baseline questionnaire were excluded.

^**Relative risks include 95% confidence intervals in parentheses. The multivariate model includes age, body mass index (6 categories), use of thiazide diuretics (yes or no), fluid intake (in quintiles), alcohol use (seven categories), family history of kidney stones (yes or no), history of hypertension (yes or no), history of diabetes (yes or no), calcium supplement use (four categories), and dietary intake of calcium, animal protein, potassium, sodium, magnesium, sucrose, and caffeine (all in quintiles).