Smokers were defined as those who had smoked at
least once cigarette per day for a period of six months
continuously. Frequency was grouped as daily, weekly,
monthly, and less than once a month. Frequency and
amount smoked were combined into number of packyears.
Alcohol drinking was defined as drinking alcohol
at least once a month continuously, including beer, wine,
wort (The product of fermentation of rice), rice whisky,
hard liquor (Lao Dang) and herbal liquor (Lao Ya Dong).
Betel quid chewing was defined as chewing all the betel
nut at least six month continuously [Or keeping the betel
nut in the buccal cavity (sulcus)]. Sexual behavior was
investigated as a potential method of infection with HPV:
we investigated the number of sexual partners and oral
sex partners.