Table 1.
Number of observations and descriptive statistics of educational years by smoking status, measurement year and sex.
| Number of observations | Never smokersa | Current smokersa | Former smokersa | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| All individuals | Discordant pairs | % | Educational years | % | Educational years | % | Educational years | ||||
| Mean | SD | Mean | SD | Mean | SD | ||||||
| Men | |||||||||||
| 1960–1969 | 5086 | 754 | 31 | 14.5 | 3.05 | 41 | 13.1 | 2.95 | 28 | 13.7 | 3.05 |
| 1970–1979 | 8246 | 867 | 32 | 8.7 | 4.10 | 40 | 7.7 | 3.10 | 28 | 8.3 | 3.62 |
| 1980–1989 | 17,204 | 1848 | 36 | 12.1 | 4.55 | 31 | 10.0 | 3.88 | 33 | 11.5 | 4.31 |
| 1990–1999 | 8378 | 922 | 44 | 11.4 | 4.34 | 26 | 10.3 | 3.99 | 35 | 10.4 | 4.37 |
| 2000–2012 | 13,764 | 1435 | 48 | 13.3 | 3.81 | 24 | 11.9 | 3.71 | 29 | 12.2 | 4.03 |
| Women | |||||||||||
| 1970–1979 | 8366 | 537 | 69 | 7.7 | 3.11 | 20 | 8.1 | 2.95 | 11 | 8.7 | 3.52 |
| 1980–1989 | 19,332 | 1526 | 56 | 10.9 | 4.16 | 26 | 10.9 | 3.55 | 18 | 11.5 | 3.86 |
| 1990–1999 | 11,138 | 1114 | 58 | 10.8 | 4.14 | 22 | 10.6 | 3.88 | 20 | 11.3 | 4.03 |
| 2000–2012 | 17,614 | 1524 | 60 | 13.1 | 4.13 | 20 | 12.2 | 3.87 | 20 | 12.7 | 3.97 |
Twin cohorts from the following countries were included in the analyses: Australia (Queensland Twin Register, Twin Research Australia), China (Qingdao Twin Registry), Belgium (East Flanders Prospective Twin Survey), Finland (FinnTwin12, FinnTwin16, Finnish Older Cohort), Hungary (Hungarian Twin Registry), Italy (Italian Twin Registry), Japan (Osaka University Aged Twin Registry), Norway (Norwegian Twin Registry), South Korea (Korean Twin-Family Register), Spain (Murcia Twin Registry), Sweden (Swedish Twin Registry, Swedish Young Male Twins Study) and USA (Mid Atlantic Twin Registry, NAS-NRC Twin Cohort, Vietnam Era Twin Registry).
aCalculated within all individuals.