Table 4. Prevalence Rate Ratios for plasma vitamin C deficiency (<11 µmol/L) compared to adequate (>28 µmol/L).

	Univariable analysis			Multivariable analysis
	PRR1	95% CI	p	PRR2	95% CI	p
Age Group
60–64	1			1
65–69	1.05	0.99, 1.10		1.07	1.02, 1.12
70–74	1.11	1.05, 1.17		1.08	1.03, 1.14
75–79	1.11	1.04, 1.19		1.09	1.02, 1.16
80+	1.17	1.09, 1.25		1.14	1.07, 1.22
P trend			<0.0001			<0.0001
Women	0.91	0.86, 0.96	<0.0001	0.93	0.89, 0.98	0.003
Lowest SES3	1.11	1.04,1 .18	<0.0001	1.03	0.99, 1.07	0.2
Biomass fuels	1.25	1.14, 1.20	<0.0001	1.03	0.98, 1.09	0.02
Malnutrition	1.13	1.07, 1.20	<0.0001
Body mass Index
<18.5	1.11	1.06,1 .16	<0.0001	1.05	1.03, 1.09	<0.001
≥18.5–<25	1			1
≥25	0.91	0.84, 0.96	0.002	0.97	0.93, 1.02	0.3
Diabetes	1.02	0.97,1.07	0.6	1.01	0.97, 1.05	0.6
Current tobacco 4
North India	1.09	1.02, 1.15	0.01	1.07	1.01, 1.13	0.02
South India	1.34	1.19, 1.50	<0.0001	1.29	1.18, 1.41	<0.0001
Dietary vitamin C5
<18	1			1
>18–29	0.88	0.83, 0.93		0.99	0.95, 1.03
>29–44	0.80	0.76, 0.86		0.95	0.91, 0.99
>44	0.73	0.68, 0.77		0.90	0.86, 0.94
P trend			<0.0001			<0.0001
Season 6
North India
December to February	1			1
March to May	1.11	0.96, 1.29	0.2	1.09	0.95, 1.25	0.2
June to September	1.33	1.21, 1.46	<0.0001	1.27	1.16, 1.38	<0.0001
October to November	1.27	1.16, 1.40	<0.0001	1.27	1.17, 1.38	<0.0001
South India
December to February	1
March to May	0.86	0.61, 0.91	0.03	0.83	0.74,0.94	0.003
June to September	0.74	0.61, 0.91	0.004	0.73	0.61,0.89	0.001
October to November	0.87	0.77, 0.99	0.04	0.91	0.78,1.06	0.2

¹Prevalence rate ratios adjusted for age and sex.

²Prevalence rate ratios adjusted for variables in the Table.

³Socio-Economic status.

⁴interaction for tobacco use and vitamin C deficiency by location, p = 0.001.

⁵Quartiles of dietary vitamin C (mg/day).

⁶interaction for season and vitamin C deficiency by location, p <0.0001.