Table 1.

Survey samples and participants (n) in the risk factor surveys and plasma vitamin C sub-samples from the district of Pitkäranta, Republic of Karelia, Russia and the province of North Karelia, Finland, spring 1992, 1997 and 2002

	Pitkäranta, Republic of Karelia, Russia				North Karelia, Finland
	Men		Women		Men		Women
	Risk factor survey	Vitamin C sub-sample	Risk factor survey	Vitamin C sub-sample	Risk factor survey	Vitamin C sub-sample	Risk factor survey	Vitamin C sub-sample
1992
Original sample	500	157		†	1000	336		†
Cleaned sample*	495				988
Participants	380	117			673	224
Participation rate (%)	77	75			68	67
1997
Original sample	499	499	501	501	1000	400		†
Cleaned sample*	486	486	500	500
Participants	309	244	440	338	712	191‡
Participation rate (%)	64	50	88	68	71	48
2002
Original sample	500	500	500	500	1000	1000	1000	1000
Cleaned sample*	472	472	481	481	994	994	993	993
Participants	263	218	342	274	664	559§	762	642||
Participation rate (%)	56	46	71	57	67	56	77	65

*Persons who had died or moved away from the study area between drawing the sample and the time of the health examination as well as persons who were in prison at the time of the study were excluded from the cleaned sample.

†Plasma vitamin C was not determined from the samples of women in 1992 in Pitkäranta and in 1992 and 1997 in North Karelia.

‡Vitamin C could not be measured in North Karelia 1997 from all samples due to technical difficulties with metaphosphoric acid used at the field laboratory.

§The plasma samples of fifty-seven men from North Karelia in 2002 were omitted because of thawing.

||The plasma samples of sixty-one women from North Karelia in 2002 were omitted because of thawing.