Reduction of the incidence and mortality of rectal cancer by polypectomy: a prospective cohort study in Haining County

Table 1 Age distribution of two groups of high-risk populations with polyps

Age Group	1a		2b		Total (%)
	Male (%)	Female (%)	Male (%)	Female (%)
30-	644 (36.6)	440 (41.6)	287 (34.4)	181 (37.2)	1552 (38.1)
40-	452 (25.7)	270 (25.6)	226 (27.1)	100 (23.7)	1049 (25.8)
50-	434 (24.7)	237 (22.4)	204 (24.4)	99 (23.5)	974 (23.9)
60-	164 (9.3)	89 (8.4)	99 (11.9)	37 (27.2)	389 (9.6)
70-	64 (3.7)	21 (2.0)	19 (2.3)	5 (1.2)	109 (2.7)
Total	1758	1057	835	422	4072

^a1: high-risk population with history of polyps identified during 1977-1978;

^b2: High-risk population identified in 1980. The age of 4 participants is unknewn