| Characteristic | Number of estimates | |||||
| Any cessation attempt | Multiple† cessation attempts | |||||
| 6-month prevalence§ | 12-month prevalence|| | Lifetime prevalence§ | 12-Month prevalence | Lifetime prevalence | Duration of cessation attempt‡ | |
| Period of adolescence | ||||||
| Early | – | 738–42 | – | – | – | – |
| Early to middle | 737 70 75 | 1435 36 42–46 53–55 57 59 60 | 937 68 70 75 | – | 337 68 74 | 537 70 74 |
| Middle | 175 | 4433 38–42 47–51 56 71 | 175 | – | 174 | 174 |
| Early to late | 730 37 75 | 122 38 40 41 47–49 52 61 72 73 | 537 75 | – | 237 74 | 437 74 |
| Middle to late | 537 | 1435 36 50 51 58 62–67 | 732 37 68 | 862–67 | 237 68 | 337 |
| Late | 175 | 1538–41 49–51 62–67 | 72 75 | 562–66 | 174 | 174 |
| Smoking status | ||||||
| Self-defined current | – | 1362–67 | 132 | 1362–67 | – | – |
| Past week | 170 | – | 170 | – | – | 170 |
| Past month | 2030 37 75 | 932 33 35 36 38–61 71 | 272 37 68 75 | – | 937 68 74 | 1337 74 |
| Smoking frequency | ||||||
| Any use | 1337 75 | 932 33 35 36 38–61 | 182 37 68 75 | – | 937 68 74 | 737 74 |
| Daily¶ | 530 37 70 | 1362–67 | 82 32 37 70 | 1362–67 | – | 437 70 |
| Non-daily | 337 | – | 337 | – | – | 337 |
| Cumulative lifetime consumption | ||||||
| ⩾100 cigarettes | 1430 37 75 | 12 | 937 | – | 337 | 937 |
| <100 cigarettes | 337 | 12 | 337 | – | – | – |
| Any consumption/not stated | 437 70 | 10433 35 36 38–67 71 | 172 32 37 68 70 75 | 1362–67 | 668 74 | 570 74 |
*The estimate, not the study, is the unit of analysis for this table. A single study could report multiple age- and smoking history-specific estimates.
†Studies differed in how multiple cessation attempts were categorised. Categories of ⩾2, ⩾3, and/or ⩾4 cessation attempts could be derived, although not across all studies. If more than one of these cessation attempt frequency categories could be derived for a given smoking characteristic and period of adolescence stratum, then, collectively, they were considered as a single estimate of the prevalence of multiple cessation attempts for that stratum (table 4).
‡Studies differed in how the length of abstinence was categorised. Durations of ⩽1 week, ⩽1 month, ⩽6 months and/or ⩽1 year could be derived, although not across all studies. If more than one of these duration categories could be derived for a given level of cigarette consumption and period of adolescence stratum, then, collectively, they were considered as a single estimate of the duration of the cessation attempt for that stratum (table 5).
§Three reports30 74 75 were based on the 1989 US Teenage Attitudes and Practices Survey. When estimates for duplicate age and/or smoking history strata were available, only Moss et al75 was considered in the calculation of summary estimates.
||Three reports provided duplicate estimates from several of the same populations.31 33 71 When estimates for duplicate age and or smoking history strata were available, they were abstracted from The Global Youth Tobaccos Survey Collaborative Group.33
¶Several studies provided a more detailed breakdown of consumption within the “daily” smoking category.30 37 In such instances only one aggregate age-specific estimate among daily smokers was counted in tabulating the number of estimates.