Demographics and characteristics for the 48 study participants
| Individual characteristics | N | Per cent |
|---|---|---|
| Male | 48 | 100 |
| Caucasian | 42 | 88 |
| Smoking status (current smoker)* | 19 | 40 |
| Other characteristics | ||
| Time of ECG (AM)† | 18 | 38 |
| Season of ECG (Winter)‡ | 33 | 69 |
| Heart problems§ | 5 | 10 |
| Mean | SD | |
| Age at start of study 2010 (years) | 40 | 12 |
| Number of years as a boilermakers (years) | 9 | 9 |
| Last weld day before study (days) | 44 | 51 |
*Current smokers versus non-smokers and previous smokers.
†Morning (AM) versus afternoon (PM).
‡Winter versus summer.
§Heart problems include reported previous history of arrhythmia, cardiac sinus problems or palpitations.