Table 1.

Sociodemographic and lifestyle characteristics of study subjects, NHANES 2011–2012 ¹, overall and by urinary iodine concentration ¹.

Characteristic	Total		Low UIC (<100 µg/L)		Normal UIC (≥100 µg/L)		Chi-Square
	n	wt’d%	n	wt’d%	n	wt’d%	2p-Value
All	1286	100	490	37.99	796	62.01
Sex
Male	666	50.62	235	16.40	431	34.22	0.0015 **
Female	620	49.38	255	21.59	365	27.79
Age
20–39 years	579	44.62	235	17.48	344	27.14	0.0160 *
40–59 years	424	38.58	175	16.38	249	22.20
≥60 years	283	16.80	80	4.13	203	12.67
Race
NHW	429	63.21	164	24.06	265	39.15	0.9865
NHB	338	12.15	128	4.53	210	7.62
NHA	221	5.80	86	2.27	135	3.53
Hispanics	298	18.83	112	7.13	186	11.70
Education
<High School	278	15.74	103	5.87	175	9.87	0.1321
High School	248	18.91	92	6.14	156	12.77
>High School	760	65.35	295	25.99	465	39.37
Poverty Income Ratio 3
Low	670	41.08	244	14.31	426	26.77	0.3670
Medium	250	21.84	100	8.71	150	13.13
High	366	37.08	146	14.97	220	22.11
Smoking 4
Low	410	37.63	149	13.75	261	23.88	0.3520
Medium	595	40.11	230	14.68	365	25.43
High	281	22.26	111	9.56	170	12.70
BMI 5
Underweight	46	3.08	22	1.32	24	1.76	0.3296
Normal	418	32.32	173	13.61	245	18.70
Overweight	412	33.10	151	11.52	261	21.58
Obese	410	31.50	144	11.54	266	19.96
Supplement 6
Yes	217	18.03	68	5.68	149	12.36	0.1056
No	1069	81.97	422	32.31	647	49.65
Alcohol
None	486	31.27	176	10.94	310	20.32	0.1274
>0 to 1 drinks/day	263	21.34	102	8.34	161	13.01
>1 to 2 drinks/day	211	19.31	90	9.27	121	10.05
>2 drinks/day	326	28.08	122	9.44	204	18.63
Physical Activity 7
None	745	51.64	276	19.93	469	31.71	0.8763
0 to <500	249	22.15	97	8.09	152	14.06
500 to <1000	161	14.09	65	5.61	96	8.48
≥1000	131	12.12	52	4.35	79	7.77
Waist Circumference
Male
≤102 cm	426	60.85	157	19.75	269	41.10	0.9767
>102 cm	240	39.15	78	12.64	162	26.50
Female
≤88 cm	260	43.70	119	20.62	141	23.08	0.1804
>88 cm	360	56.30	136	23.11	224	33.20

¹ Data are from the National Health and Nutrition Examination Survey. All data except for sample size are weighted to account for the complex study design according to the guidelines of the National Center for Health Statistics. Values are reported as n (weighted percentage). Total of percentages may exceed 100 due to rounding. ² p value obtained from the Wald chi-square test (* p < 0.05, ** p < 0.01). ³ PIR, family poverty-income ratio (low: 0–1.85; medium: 1.85< to 3.5; high: >3.5). ⁴ Smoking status defined by a serum cotinine concentration (low: <0.015 mg/L; medium: 0.015 to <10 mg/L; high: ≥10 mg/L). ⁵ BMI: Underweight: <18.5 kg/m²; normal weight: 18.5 to >25 kg/m²; overweight: 25 to <30 kg/m²; and obese: ≥30 kg/m². ⁶ Reported taking supplement containing iodine within the past 30 days. ⁷ Calculated as total MET (metabolic equivalent task minutes)-min/week from self-reported leisure-time physical activities. UIC, urinary iodine concentration; NHW, non-Hispanic white; NHB, non-Hispanic black.