Table 2.

Association of Cataract with Plasma Vitamin C

Plasma Vitamin C (μmol/L)	North India		South India		Both Centers
Nuclear Cataract	Model 1⁎	Model 2†	Model 1⁎	Model 2†	Model 1⁎	Model 2†
Q1	1	1	1	1	1	1
Q2
OR	0.74	0.79	0.86	0.83	0.76	0.78
95% CI	0.53–1.02	0.58–1.09	0.64–1.17	0.62–1.12	0.60–0.95	0.63–0.98
Q3
OR	0.51	0.56	0.85	0.89	0.64	0.69
95% CI	0.37–0.70	0.40–0.79	0.66–1.10	0.69–1.14	0.51–0.79	0.56–0.86
Q4
OR	0.44	0.52	0.62	0.69	0.50	0.58
95% CI	0.32–0.61	0.38–0.72	0.48–0.81	0.54–0.89	0.41–0.62	0.47–0.72
P trend§	1.5 × 10−8	3.5 × 10−6	0.0002	<0.01	8.0 × 10−11	4.7 × 10−7
P interaction∥					0.07	0.12
Cortical cataract
Q1	1	1	1	1	1	1
Q2
OR	0.79	0.84	0.87	0.91	0.83	0.88
95% CI	0.52–1.21	0.56–1.28	0.53–1.43	0.56–1.47	0.60–1.14	0.64–1.20
Q3
OR	0.61	0.64	0.68	0.70	0.65	0.68
95% CI	0.42–0.91	0.43–0.95	0.47–0.99	0.48–1.04	0.50–0.85	0.52–0.89
Q4
OR	0.66	0.74	0.60	0.63	0.61	0.65
95% CI	0.39–1.11	0.45–1.20	0.44–0.83	0.47–0.86	0.47–0.80	0.50–0.85
P trend§	0.02	0.06	0.001	0.003	0.0001	0.001
P interaction∥					0.96	0.91
PSC cataract
Q1	1	1	1	1	1	1
Q2
OR	0.70	0.70	1.05	1.03	0.79	0.79
95% CI	0.50–0.99	0.49–0.99	0.76–1.45	0.76–1.40	0.61–1.03	0.61–1.02
Q3
OR	0.55	0.56	0.89	0.93	0.66	0.68
95% CI	0.37–0.82	0.37–0.86	0.67–1.17	0.70–1.22	0.51–0.85	0.52–0.89
Q4
OR	0.42	0.44	0.68	0.69	0.51	0.53
95% CI	0.30–0.59	0.32–0.61	0.53–0.86	0.54–0.89	0.41–0.64	0.42–0.66
P trend§	1.8 × 10−6	0.00001	0.001	0.004	1.7 × 10−8	2.7 × 10−7
P interaction∥					0.08	0.10

CI = confidence interval; OR = odds ratio; PSC = posterior subcapsular cataract.

^⁎Adjusted for age and sex.

^†Adjusted for age, sex, tobacco use, current fuels, BMI, mid-upper arm circumference, diastolic blood pressure, outdoor exposure, diabetes, and socioeconomic status.

^§Test for trend by design-adjusted Wald test with 4 ordered categories of vitamin C entered as independent continuous variable.

^∥Test for interaction by center and vitamin C by design-adjusted chi-square test.