Table 2.
Mean plasma vitamin C concentration (μmol/l), cut-off points for plasma vitamin C tertiles (μmol/l) and number of participants in the tertiles in Pitkäranta, Republic of Karelia, Russia and North Karelia, Finland, in spring 1992, 1997 and 2002†
| Mean plasma | Cut-off points for plasma vitamin C tertiles (μmol/l) | Number of participants | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Data | Sex | vitamin C (μmol/l) | Lowest tertile | Middle tertile | Highest tertile | Lowest tertile | Middle tertile | Highest tertile | Total |
| Pitkäranta | |||||||||
| 1992 | Men | 2·5 | 0·57 | 1·14–6·25 | 6·81–32·93 | 95 | 11 | 11 | 117 |
| 1997 | Men | 8·0 | 0·28–2·27 | 2·84–6·81 | 7·38–65·86 | 81 | 79 | 84 | 244 |
| Women | 22·1 | 0·28–7·38 | 7·95–24·42 | 24·98–102·20 | 116 | 110 | 112 | 338 | |
| 2002 | Men | 5·0 | 0 | 0·40–3·24 | 3·29–43·78 | 73 | 73 | 72 | 218 |
| Women | 12·6 | 0–2·95 | 3·07–14·82 | 14·99–66·38 | 93 | 89 | 92 | 274 | |
| North Karelia | |||||||||
| 1992 | Men | 53·9 | 2·21–47·52 | 47·64–60·70 | 60·75–112·99 | 75 | 74 | 75 | 224 |
| 1997 | Men | 27·1 | 0·57–19·31 | 19·87–32·93 | 33·50–82·90 | 64 | 65 | 62 | 191 |
| 2002 | Men | 37·3 | 0–27·88 | 28·05–43·89 | 44·00–134·23 | 185 | 187 | 187 | 559 |
| Women | 43·6 | 2·56–35·43 | 35·49–49·68 | 49·85–189·08 | 213 | 215 | 214 | 642 | |
†
In 1992 and 1997, metaphosphoric acid was used for plasma stabilization and plasma vitamin C measurement included ascorbic acid and dehydroascorbic acid. In 2002, as a result of change in method, only the concentration of ascorbic acid was determined.