Table 1.

Characteristics of the participants.

	All Participants			Biochemistry Subset
Variables	Arid Desert Group n = 246	Control Group n = 574	p	Arid Desert Group n = 75	Control Group n = 96	p
Age			0.096			0.473
≤20 years	122, 49.6%	241, 42.0%		38, 50.70%	40, 41.70%
21–25 years	104, 42.3%	268, 46.7%		30, 40.0%	47, 48.90%
≥26 years	20, 8.1%	65, 11.3%		7, 9.30%	9, 9.40%
Length of military service			0.094			0.481
≤2 years	168, 68.3%	363, 63.2%		51, 68.0%	61, 63.5%
3–7 years	62, 25.2%	146, 25.4%		20, 26.7%	25, 26.0%
≥8 years	16, 6.5%	65, 11.3%		4, 5.3%	10, 10.4%
Ethnicity			<0.001			0.022
Han	235, 95.5%	495, 86.2%		72, 96.0%	82, 85.4%
Minority	11, 4.5%	79, 13.8%		3, 4.0%	14, 14.6%
Education			0.971			0.995
Junior and senior	179, 72.8%	414, 72.1%		53, 70.7%	68, 70.8%
Big and secondary	53, 21.5%	128, 22.3%		16, 21.3%	20, 20.8%
University or above	14, 5.7%	32, 5.6%		6, 8.0%	8, 8.3%
Marital status			0.008			0.076
Married	11, 4.5%	58, 10.1%		2, 2.7%	9, 9.40%
Unmarried	235, 95.5%	516, 89.9%		73, 97.3%	87, 90.60%
Household registration before recruitment			<0.001			0.425
Urban	194, 78.9%	370, 64.5%		55, 73.3%	65, 67.7%
Rural	52, 21.1%	204, 35.5%		20, 26.7%	31, 32.3%
Only child			0.581			0.787
Yes	69, 28.0%	172, 30.0%		22, 29.3%	30, 31.3%
No	177, 72.0%	402, 70.0%		53, 70.7%	66, 68.8%
Monthly family income			0.636			0.801
≤1000 yuan	27, 11.0%	78, 13.6%		8, 10.7%	12, 12.5%
1000–4000 yuan	34, 13.8%	91, 15.9%		11, 14.7%	16, 16.7%
4000–7000 yuan	46, 18.7%	107, 18.6%		15, 20.0%	19, 19.8%
7000–1000 yuan	91, 37.0%	185, 32.2%		29, 38.7%	29, 30.2%
≥10,000 yuan	48, 19.5%	113, 19.7%		12, 16.0%	20, 20.8%
Rank level			0.438			0.918
Officer	11, 4.5%	31, 5.4%		3, 4.0%	5, 5.2%
Sergeancy	68, 27.6%	180, 31.4%		22, 29.3%	29, 30.2%
Conscripts	167, 67.9%	363, 63.2%		50, 66.7%	62, 64.6%

* p < 0.05.