Table 2. Hazard ratios for incidence of kidney stones by potential confounders, 1985 to 2004–05.

Variable	Participants	Person-years of follow-up	Incidence	Incidence (per 10 000 person-years)	Age-adjusted hazard ratio (95% CI)	P for trend	Multivariablea Hazard Ratio (95% CI)	P for trend
Age
Per 10 years	4074	77 406	258	33	—	—	0.93 (0.72–1.21)	0.601
Systolic blood pressure
Per 10 mm Hg	4074	77 406	258	33	1.04 (0.94–1.16)	0.425	1.02 (0.91–1.14)	0.770
Cardiorespiratory fitness, mL/kg/min
1st tertile (<37.3)	1289	24 491	90	37	1.00 (Reference)		1.00 (Reference)
2nd tertile (37.3–43.5)	1376	26 144	91	35	0.93 (0.69–1.25)		1.02 (0.75–1.38)
3rd tertile (>43.5)	1409	26 771	77	29	0.75 (0.55–1.03)	0.079	0.85 (0.60–1.19)	0.347
Cigarette smoking, cigarettes/day
None	1357	25 783	86	33	1.00 (Reference)		1.00 (Reference)
1–20	1599	30 381	89	29	0.87 (0.65–1.17)		0.89 (0.66–1.20)
≥21	1118	21 242	83	39	1.18 (0.87–1.59)	0.324	1.20 (0.89–1.63)	0.265
Alcohol consumption, g/day
None	1261	23 959	94	39	1.00 (Reference)		1.00 (Reference)
1–45	2607	49 533	153	31	0.78 (0.60–1.01)		0.76 (0.59–0.99)
≥46	206	3914	11	28	0.71 (0.38–1.33)	0.056	0.64 (0.34–1.21)	0.031

CI, confidence interval.

^aAdjusted for all items in the table plus body mass index.