What defines a chronic smoker?

Definition of a Chronic Smoker

A chronic smoker is defined as a person who reports currently smoking tobacco every day and has smoked at least 100 cigarettes (5 packs) in their lifetime. 1

Clinical Definitions Based on Smoking Status

• Current everyday user: A person who reports currently smoking tobacco every day and has smoked at least 100 cigarettes (5 packs) in their lifetime 1
• Current some day user: A person who reports currently smoking tobacco on some days (nondaily smoker) and has smoked at least 100 cigarettes (5 packs) in their lifetime 1
• Former user: A person who does not currently smoke tobacco but has smoked at least 100 cigarettes in their lifetime 1
  • Long-term abstinence is often operationally defined as 6 months of abstinence 1
  • Abstinence from smoking for at least 7 days in a row is the criterion often required in clinical studies for an individual to be considered a former smoker in the short term 1
• Never user: A person who has not smoked tobacco regularly and does not now smoke every day or some days; defined as an individual who has not smoked 100 cigarettes (5 packs) in their lifetime 1

Quantification of Smoking Exposure

• Pack-years: The standard measurement for quantifying lifetime tobacco exposure 1
  • One pack-year is defined as smoking 20 cigarettes per day for 1 year 1
  • This measurement is critical for assessing long-term health risks 2

Clinical Significance of Smoking Thresholds

• 20 pack-years: An important threshold used in lung cancer screening guidelines 2

  • Individuals with ≥20 pack-year smoking history should be evaluated for lung cancer screening eligibility 2
  • Former smokers with more than 20 pack-years have a 3.06-fold increased risk of lung cancer mortality compared to never smokers 2

• Heavy smokers: Often defined as those who smoke 25 or more cigarettes per day 3

  • These individuals constitute approximately 26.7% of all cigarette smokers 3
  • They are more likely to smoke their first cigarette within 30 minutes of waking, indicating higher nicotine dependence 3

Health Implications of Chronic Smoking

• Chronic smokers have significantly higher risks of all-cause mortality, with risk persisting even after cessation 2
• Former smokers with >20 pack-years still have a 2.20-fold increased risk of lung cancer mortality even after 25 years of smoking cessation 2
• Smoking is the single most important cause of COPD, with risk directly proportional to tobacco exposure 1

Important Clinical Considerations

• Many individuals who currently smoke fewer cigarettes per day likely smoked substantially higher numbers earlier in their lives, which affects their overall risk profile 4
• Even low-intensity smoking (fewer than 10 cigarettes per day) is associated with significantly increased mortality risk compared to never smokers 4
• There is no risk-free level of exposure to tobacco smoke 4
• Approximately 70% of people who smoke cigarettes want to quit, but individuals typically make about 6 quit attempts before achieving long-term abstinence 5

Treatment Implications

• First-line therapy for smoking cessation should include both pharmacotherapy and behavioral support 5
• Varenicline or combination nicotine replacement therapy (NRT) are preferred initial interventions for smoking cessation 5
• The combination of medication and behavioral counseling is associated with higher quit rates (15.2%) compared to brief advice or usual care (8.6%) 5