Smoking and Health Risks: Study Summary

Background

• Smoking is known to increase the risk of contracting pneumonia.
• There are mixed results on whether smoking affects the risk of death from pneumonia.
• Study Aim: To investigate the association between smoking, the risk of contracting infections and pneumonia, and subsequent mortality.

Methodology

• Participants: Swedish men and women from the Swedish Cohort of Men and the Swedish Mammography Cohort.
• Data collected from national registers in Sweden.
• Statistical Tool: Cox regression to assess the risk of infections and death.
• Sample Size: 62,902 participants, of which 25,297 contracted an infection and 10,471 contracted pneumonia. 4,505 died from infections, and 2,851 died from pneumonia.
• Analysis Variables: Smoking status at baseline, number of cigarettes (pack-years), years since smoking cessation.

Key Findings

• Former Smokers:
  • Hazard Ratio (HR) for contracting infection: 1.08
  • HR for dying from infection: 1.19
  • HR for contracting pneumonia: 1.17
  • HR for dying from pneumonia: 1.16
• Current Smokers:
  • HR for contracting infection: 1.17
  • HR for dying from infection: 1.64
  • HR for contracting pneumonia: 1.42
  • HR for dying from pneumonia: 1.70
• Risk increased with the number of pack-years and decreased with years since cessation.

Conclusion

• Smoking increases the risk of contracting and dying from infections and pneumonia.
• Importance of smoking cessation and primary prevention emphasized.

Detailed Study Insights

Participants

• Cohort of Swedish Men: Men from Västmanland and Örebro.
• Swedish Mammography Cohort: Women from Uppsala and Västmanland.

Exposure and Confounders

• Smoking details collected via questionnaires: regular smoking status, cessation history, number of cigarettes smoked over different age periods.
• Confounders: Education, marital status, exercise, alcohol consumption, Charlson's comorbidity index.

Outcomes

• Contracting any infection or pneumonia, ICU admissions, death data collected from national health registers.
• ICD-10 codes were used to classify infections and pneumonia cases.

Statistical Analyses

• Hazard Ratios calculated using Cox proportional hazards regression.
• Sensitivity analyses included adjusting for self-rated health, BMI, time since baseline, and specific analyses on 30-day mortality from pneumonia.

Results

• Risk of Infection:
  • Former smokers show increased risk compared to never smokers.
  • Current smokers at higher risk of ICU admission and death from infections.
• Pneumonia Analysis:
  • Former and current smokers have higher risks compared to never smokers.
  • Dose-response relationship with pack years smoked and time since cessation.

Discussion

• Former and current smokers are at a higher risk of infection and pneumonia.
• Contradicts some previous findings suggesting lower mortality risk among smokers.
• Highlights importance of smoking cessation policies.
• Study strengths include large sample size and reliable national data registers.

Limitations

• Smoking status might change over time, affecting consistency.
• Lack of microbiological data may limit insights on specific bacterial infections.
• Findings primarily applicable to Swedish populations.

Acknowledgments

• Supported by Swedish national research infrastructure and data from Swedish Intensive Care Registry.
• No specific funding acquired for the study.

Data Availability

• Data access restricted to researchers with ethical approval from SIMPLER steering committee.

References

• Cited studies and statistical data sources included in the publication.