The factors studied were:general condition,smoking and drin- king,diet habit,individual disease history,marriage and birth history,soci- allife psychology,genetic factors,etc.

• 研究因素有被调查者的一般情况、烟酒嗜好、饮食习惯、个人患病史、婚姻及生育史,社会生活和遗传因素等。