Table 2 . Demographic data of the study population.

	Participants interviewed	Number valid	Samples collected	Percent male	Percent rural	Mean age±SD(yr)
Tehran	2561	2561	2290	41.5%	5.1%	35.6 ± 13.6
Hormozgan	1987	1745	1403	44.6%	0%	33.4 ± 11.9
Golestan	2035	1896	1896	32.0%	48.2%	38.8 ± 12.9
Total	6583	6202	5589	39.3%	18.4%	36.1 ± 13.1