Table 1.

Characteristics of Nasopharyngeal Carcinoma Cases and Controls Enrolled in a Population-Based Case-Control Study in Southern China, 2010–2014

Characteristic	Case Group (n = 2,532)		Control Group (n = 2,597)		P Value
	No.	%	No.	%
Residential area					0.3
Zhaoqing	1,286	50.8	1,321	50.9
Wuzhou	688	27.2	665	25.6
Guiping/Pingnan	558	22.0	611	23.5
Sex					0.97
Male	1,860	73.5	1,909	73.5
Female	672	26.5	688	26.5
Age at diagnosis/interview, years
Overalla	48.54 (10.70)		49.75 (10.90)		<0.001b
20–34	232	9.2	207	8.1	0.07
35–39	277	11.0	246	9.5
40–44	418	16.5	399	15.4
45–49	492	19.4	491	18.9
50–54	333	13.2	347	13.4
55–59	353	13.9	382	14.7
60–74	427	16.9	525	20.2
Educational level, years					0.004
≤6	1,005	39.7	932	35.9
7–9	1,013	40.0	1,040	40.1
10–12	407	16.1	484	18.6
>12	107	4.2	141	5.4
Current housing type					<0.001
Building (concrete structure)	1,820	71.9	2,019	77.7
Cottage (clay brick structure)	702	27.7	575	22.1
Boat	10	0.4	2	0.1
Missing	0	0	1	0.04
Current occupation					<0.001
Unemployed	78	3.1	96	3.7
Farmer	855	33.8	984	37.9
Blue-collar	1,023	40.4	900	34.7
White-collar	350	13.8	416	16.0
Other/unknown	226	8.9	201	7.7
Cigarette smoking					0.12
Current smoker	1,121	44.3	1,213	46.7
Former smoker	182	7.2	152	5.9
Never smoker	1,228	48.5	1,230	47.4
Missing	1	0.04	2	0.1
First-degree family history of NPC					<0.001
No	2,208	87.2	2,483	95.6
Yes	272	10.7	70	2.7
Unknown	46	1.8	43	1.7
Missing	6	0.2	1	0.04
Alcohol drinking					0.11
Never	1,735	68.5	1,815	69.9
Ever	791	31.2	766	29.5
Missing	6	0.2	16	0.6
Tea drinking					<0.001
Never	1,618	63.8	1,513	58.3
Ever	911	36.0	1,081	41.6
Missing	3	0.1	3	0.1
Salt-preserved fish consumption in adult diet, categoryc					<0.001
1	846	33.4	797	30.7
2	489	19.3	583	22.5
3	488	19.3	582	22.4
4	678	26.8	596	23.0
Missing	31	1.2	39	1.5
Herbal medicine use					0.03
Nonusers	355	14.0	419	16.1
Yearly	965	38.1	974	37.5
Monthly	905	35.7	942	36.3
Weekly or more often	269	10.6	220	8.5
Missing	38	1.5	42	1.6

Abbreviation: NPC, nasopharyngeal carcinoma.

^a Values are expressed as mean (standard deviation).

^bP value was determined by a 2-sided t test. Other P values were determined by a χ² test.

^c Energy-adjusted intake categories: 1 = lowest intake (none) to 4 = highest intake.