Table 1. Characteristics of first- and second-degree relatives of 1211 NPC probands in Sweden, 1961–2009.

Characteristics	First-degree relatives (N=3645)	Second-degree relatives (N=5512)
Mean age at study entry, years (s.d.)	15.1 (15.3)	3.1 (10.2)
Age group at entry, no. (%)
0–4	1220 (33.5)	4910 (89.1)
5–9	380 (10.4)	104 (1.9)
10–29	1538 (42.2)	266 (4.8)
30–49	342 (9.4)	160 (2.9)
50+	165 (4.5)	72 (1.3)
Median duration of follow-up, years	49.0	33.2
Total no. of person-years at risk	150 902	176 724
No. of cancer cases	453	192
Mean age at end of follow-up, years (s.d.)	56.5 (17.0)	35.2 (16.5)

Abbreviations: No.= number; NPC=nasopharyngeal carcinoma.