Date source
The China Health and Nutrition Survey (CHNS) is a longitudinal survey and open cohort conducted from 1989 to the currently available 2015 wave, with multistage and random cluster procedures. This comprehensive dataset aims to study the influences of nutrition, health, and family planning policies established by both national and local government agencies in China. Furthermore, the CHNS investigates the impact of social and economic transitions in Chinese society on residents’ overall health and nutrition status. In the 2015 CHNS wave, a total of 15,291 individuals from nine provinces (Liaoning, Heilongjiang, Jiangsu, Shandong, Henan, Hubei, Hunan, Guangxi, and Guizhou) and three municipalities (Beijing, Chongqing, and Shanghai) were surveyed.
In this study, we used the data of adult population (aged 18 and over) in the 2015 CHNS wave (n = 12,872). After excluding those with missing socio-demographic, diet related variables, and self-rated health information, a total of 12,814 subjects were involved in the final analysis.
We used de-identified and publicly-available datasets from the official CHNS website (https://www.cpc.unc.edu/projects/china). Hence, approvals from Institutional Review Boards were not required at authors’ institutions.
Variables
Diet-related knowledge
We applied two variables to assess diet-related knowledge: the awareness of Chinese diet pagoda or Dietary Guidelines for Chinese Residents (DGCR) and adequate dietary knowledge literacy. The awareness of diet pyramid/ DGCR was identified by a question “Do you know about the Chinese Pagoda or the Dietary Guidelines for Chinese Residents (yes/no)?” Dietary knowledge literacy was computed from 17 dietary questions. Referring to the statistical analysis of Chinese residents health literacy monitoring [17] and previous relevant article [18], individuals with the actual dietary knowledge score ≥ 80% were defined as having adequate dietary knowledge literacy (i.e. the total score of 17 dietary questions ≥ 14).
17 questions which originally coded as “strongly disagree”, “disagree”, “neutral”, “agree”, and “strongly agree” in the 2015 CHNS questionnaire was transferred into dichotomous variables. For seven negative items (Q2, Q4, Q6, Q12, Q14, Q15, Q16), the response of “strongly disagree” or “disagree” was scored 1 point, otherwise 0. For the other ten positive items, the response of “strongly agree” or “agree” was scored 1 point, otherwise 0. Cronbach’s alpha for the 17 dietary questions was 0.86 in this study.
Diet-related attitude
The attitude towards the importance of “eating a healthy diet” were selected as diet-related attitude measurement. The answers were dichotomized to positive attitude (“very important” or “the most important”) and non-positive attitude (“not important at all”, “not very important”, or “neutral”).
Diet-related behaviors
Two categorical variables were applied to assess diet-related behaviors: actively looking for nutrition knowledge, and prefer eating fruits & vegetables. The behavior of looking for nutrition knowledge was measured by a question “Do you proactively look for nutrition knowledge (yes/no)?” The response of “yes” was referred to as positive behavior. The question regarding behavior of eating fruits & vegetables were dichotomized to positive behavior (“like” and “like very much”) and non-positive behavior (“dislike very much”, “dislike”, “neutral”).
Self-rated health
Self-rated health was assessed by the question “How do you rate the quality of your life at present?” The original coding included “very good”, “good”, “fair”, “bad”, and “very bad”. The response of “very good” and “good” was recognized as good health, “fair” as moderate health, “bad” and “very bad” as poor health.
Covariates
Covariates including age, gender, marital status, education level, work status, and place of residence were collected. Age was classified into three categories (18-44, 45-59, and ≥60). Marital status was dichotomized into married and others (never married, divorced, widowed, separated, etc.). Education level was classified into four categories (elementary school and below, middle school, high school, and college and above). Work status was classified into two categories (yes and no). Place of residence was dichotomized into urban and rural.
Statistical analysis
Data analysis was performed by using IBM SPSS Statistics Version 22.0 (SPSS, Inc., Chicago, IL). Descriptive statistics including means and standard deviation (SD), frequency and percentages were calculated. Comparison of diet-related knowledge, attitude, and behaviors among urban and rural residents were conducted using chi-square test. Ordinal logistic regression was conducted yielding adjusted odds ratios (ORs) to identify the association between diet-related KABs and self-rated health. In all analyses, a p-value of ≤ 0.05 was considered significant.