最近精读的文献题目为：Smoking Cessation, Weight Change, Type 2 Diabetes, and Mortality

1. Summary

• Who: Yang Hu, S.M., Geng Zong
• How: To estimate risks of type 2 diabetes, death from cardiovascular diseases, and death from any cause among those who had reported quitting smoking, according to weight changes after smoking cessation.
• What: The risk peaked 5 to 7 years after quitting and then gradually decreased. The temporary increase in the risk of type 2 diabetes was directly proportional to weight gain. In contrast, quitters did not have a temporary increase in mortality, regardless of weight change after quitting.
• Why: Whether weight gain after smoking cessation attenuates the health benefits of quitting is unclear.

2. Elegant and concise descriptions

• The risk peaked 5 to 7 years after quitting and then gradually decreased. The temporary increase in the risk of type 2 diabetes was directly proportional to weight gain, and the risk was not increased among quitters without weight gain (P<0.001 for interaction). In contrast, quitters did not have a temporary increase in mortality, regardless of weight change after quitting.
• Quitters were mutually exclusively defined as transient quitters (participants who reported being past smokers in the current cycle but being current smokers in previous and next cycles), recent quitters (2 to 6 consecutive years since smoking cessation), and long-term quitters (>6 consecutive years since smoking cessation).
• Because the biennial weight-change trajectory overlapped with that of persons who had never smoked after 6 years of cessation.
• The hazard ratios as compared with current smokers were 1.08 (95% confidence interval [CI], 0.93 to 1.26) among recent quitters without weight gain, 1.15 (95% CI, 0.99 to 1.33) among those with weight gain of 0.1 to 5.0 kg, 1.36 (95% CI, 1.16 to 1.58) among those with weight gain of 5.1 to 10.0 kg, and 1.59 (95% CI, 1.36 to 1.85) among those with weight gain of more than 10.0 kg.
• The corresponding hazard ratios for death from any cause were 0.81 (95% CI, 0.73 to 0.90), 0.52 (95% CI, 0.46 to 0.59), 0.46 (95% CI, 0.38 to 0.55), 0.50 (95% CI, 0.40 to 0.63), and 0.57 (95% CI, 0.54 to 0.59).
• Cubic spline analyses showed that cardiovascular mortality decreased substantially after quitting, reached a nadir at 10 to 15 years, and then rose slowly but never reached the level of current smokers (Fig. 2A). In stratified analyses, such a pattern of associations was observed in all weight gain groups, but among those without weight gain, cardiovascular mortality decreased after quitting for 5 to 10 years and plateaued thereafter without the upward trend.
• However, both cardiovascular and all-cause mortality decreased on smoking cessation, and the reduction was largely sustained during extended duration of smoking cessation, even among those who gained weight.

3. Pros and cons
Pros: The long-term, repeated assessments of subsequent changes in smoking status and body weight, the more accurate classification of smoking status, the use of cubic splines and three-dimensional illustration
Cons: Measurement error and misclassification bias (to bias the true associations toward the null), the lack of generalizability

4. New knowledge

• The classification of smoking cessation

• The adjustment of multiplicity of using false discovery rate

• The calculation of mediation effect

5. Questions

• Authors did not mention the lacking of laboratory results in covariates
• Authors did not adjust history of diabetes in the analyses of mortality

• Authors did not explain a more significant reduction in the risk of both cardiovascular and all-cause mortality after smoking cessation among quitters who gained weight