Author + information
- Jun Lv, PhD,
- Lu Qi, PhD and
- Liming Li, MPH∗ ()
- ↵∗Department of Epidemiology and Biostatistics, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, China
We thank Dr. Gaye and colleagues for raising thoughtful points. In the present China Kadoorie Biobank (CKB) study, we defined the low-risk lifestyle according to previous studies, recent guidelines for cardiovascular health, and the distribution of the related variables in the CKB population.
For smoking, we included former smokers who had stopped smoking because of illness in the current smoker category, because approximately one-half of former smokers in the CKB population quit due to illness (1). Such a definition might minimize potential bias of spuriously elevated risk related to this group. We followed our previous publications to define former smokers as those who had stopped smoking for reasons other than illness for ≥6 months (1,2). In addition, we changed the definition of smoking cessation from ≥6 months to ≥12 months. Of 13,112 former smokers who had stopped smoking for reasons other than illness for ≥6 months, 596 (4.6%) participants who had stopped smoking at <1 year were included in the current smoker category. The results were not materially changed.
The food frequency questionnaire used in the CKB study set only a few frequency options for each food item, including daily, 4 to 6 days per week, 1 to 3 days per week, monthly, and never/rarely, and did not include questions about portion size. Such limitations of the food frequency questionnaire precluded us from using both frequency and portion size information to define a more accurate cutoff point for dietary intake. In the current study, we had to use limited frequency options to define the low-risk group as those who ate vegetables and fruits every day. We acknowledge that the definition of low risk used in the current study may underestimate the beneficial effect of adhering to a healthy diet.
Please note: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation