Plasma Epstein-Barr virus DNA and risk of nasopharyngeal carcinoma in a prospective seropositive population

BMC Cancer

Table 2 Univariate and multivariable Cox analyses for risk factors of NPC

Variables	Participants(n)	Person-Years	NPC Cases(n)	Incidence Rate Per 100,000 Person-Years	Crude HR(95%CIs)	*P-value*	Fully Adjusted HR(95%CIs)^b	*P-value*
Sex
male	649	4009.16	18	448.97	Reference		Reference
female	714	4405.70	12	272.37	0.611 (0.294–1.269)	0.186	1.381 (0.413–4.617)	0.601
Age
30–49	688	4470.52	15	335.53	Reference		Reference
50–69	675	3944.34	15	380.29	1.099 (0.537–2.250)	0.796	0.832 (0.389–1.783)	0.637
Smoking
never	799	4929.13	11	223.16	Reference		Reference
current or former	564	3485.73	19	545.08	2.415 (1.149–5.076)	0.020	3.566 (1.055–12.060)	0.041
Salted food
monthly or less	1171	7073.05	25	353.45	Reference		Reference
weekly and more	192	1341.81	5	372.63	1.050 (0.402–2.745)	0.921	0.867 (0.329–2.288)	0.774
Family history
no	1302	8025.25	25	311.52	Reference		Reference
yes	61	389.61	5	1283.34	4.227 (1.618–11.043)	0.003	2.838 (1.029–7.826)	0.044
Education
≤ 6 year	488	2967.21	14	471.82	Reference		Reference
> 6 year	875	5447.65	16	293.70	0.638 (0.312–1.308)	0.220	0.433 (0.191–0.982)	0.045
EBV DNA (copies/ml)
≤ 3(undetectable)	1324	8171.70	23	281.46	Reference		Reference
> 3 (detectable)	39	243.16	7	2878.70	10.476 (4.495–24.414)	< 0.0001	10.049 (4.227–23.887)	< 0.0001
> 3–999	35	223.31	5	2239.01	8.123 (3.088–21.370)		7.627 (2.83–20.558)
≥ 1000	4	19.85	2	10,074.47	37.763 (8.890–160.414)	< 0.0001^a	39.789 (8.406–188.348)	< 0.0001

^aP trend for the comparision among EBV DNA undetectable group, DNA levels at > 3–999 copies/ml and DNA levels ≥1000 copies/ml
^b Maximum adjustment: all the aforementioned variables were used for adjustment including sex, age, smoking status, NPC family history, salted food,education level, EBV DNA

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