Socioeconomic gradients in the Westernization of diet in China over 20 years.

INTRODUCTION: In low-middle income countries, urbanization leads to changes from traditional to Western diet, which are often accompanied by reductions in cardiometabolic health. Whether socioeconomic status buffers these urbanization-related diet changes over time is unknown. OBJECTIVE: To examine whether the association between urbanization and a key indicator of Western diet, percent of calories from animal-source foods (1) varies depending on income and (2) whether this association changes over time. MATERIALS AND METHODS: We used data from nine waves of the longitudinal, population-based China Health and Nutrition Survey [n = 22,360 Chinese adults (1991-2015)], followed across 24 years, including diet data from 3 repeated 24-h dietary recalls. We used simultaneous year-stratified linear regression models to examine whether changes in the association between urbanization level and percent of calories from animal-source foods differed by income. Models allowed for variation in associations across the 24 years of urbanization, accounting for within-individual correlation over time and controlling for age, sex, region, physical activity, and caloric intake. RESULTS: In 1991, on average 15% of calories for Chinese adults came from animal source foods and by 2015, this percentage rose to approximately one quarter of total calories. Over the 24 years of follow-up, urbanization and income were each strongly related to percent of calories from animal-source foods with differential association across income levels (p < 0.0001). We also found evidence that this association changed over time (p < 0.0001). Income gradients in animal source food consumption were smallest in the most urban areas in early years with some temporal variation, but over time income gradients narrowed in some later years in low and moderately urbanized areas. However, by 2015 there were few income differences in animal source food consumption across urbanization levels. CONCLUSIONS: Throughout 24-years of urbanization, income seemed to buffer the transition from traditional to Western diet. However, the degree to which income buffered these urbanization-related changes depended on the level and history of community urbanization. At later stages of urbanization when Western diet behaviors were more widespread, urban-rural differences in Western diet behaviors varied little by income.

Accounting for Selectivity Bias and Correlation Across the Sequence From Elevated Blood Pressure to Hypertension Diagnosis and Treatment.

BACKGROUND: It is unknown whether efforts to reduce hypertension burden in countries with very high prevalence, would be more effective if directed at hypertension diagnosis vs. treatment. Most analyses do not address bias and correlation across the sequence from elevated blood pressure (BP) to hypertension diagnosis and treatment, leading to potentially misleading findings. METHODS: Using data spanning 18 years of the China Health and Nutrition Survey (n = 18,926; ages 18-75 years), we used an innovative 3-step, integrated system of equations to predict the sequence from: (i) elevated BP (systolic/diastolic BP ≥ 140/90 mm Hg) to (ii) diagnosed hypertension conditional on elevated BP, and to (iii) treatment (medication use) conditional on diagnosis, accounting for measured and unmeasured individual- and community-level confounders at each of the 3 steps. We compared results to separate traditional logistic regression models without control for unmeasured confounding. RESULTS: Using our 3-step model, elevated BP increased from 12.6% and 8.5% (1991) to 36.8% and 29% (2009) in men and women, respectively, but diagnosis remained under 50%. We found widening disparities in hypertension diagnosis (higher hypertension at lower vs. higher education (difference of 2% in 1991 that widened to 5% in 2009)) and narrowing disparities in education (difference of 6% in 1991 to 4% in 2009) and insurance status (difference of 7% in 1991 to 2% in 2009) for treatment. CONCLUSIONS: Our 3-step model improved model fit over traditionally used models. Our findings highlight serious barriers to hypertension diagnosis in Chinese adults, particularly among men and individuals of low attained education.

Differential associations of urbanicity and income with physical activity in adults in urbanizing China: findings from the population-based China Health and Nutrition Survey 1991-2009.

BACKGROUND: High urbanicity and income are risk factors for cardiovascular-related chronic diseases in low- and middle-income countries, perhaps due to low physical activity (PA) in urban, high income areas. Few studies have examined differences in PA over time according to income and urbanicity in a country experiencing rapid urbanization. METHODS: We used data from the China Health and Nutrition Survey, a population-based cohort of Chinese adults (n = 20,083; ages 18-75y) seen a maximum of 7 times from 1991-2009. We used sex-stratified, zero-inflated negative binomial regression models to examine occupational, domestic, leisure, travel, and total PA in Chinese adults according to year, urbanicity, income, and the interactions among urbanicity, income, and year, controlling for age and region of China. RESULTS: We showed larger mean temporal PA declines for individuals living in relatively low urbanicity areas (1991: 500 MET-hours/week; 2009: 300 MET-hours/week) compared to high urbanicity areas (1991: 200 MET-hours/week; 2009: 125 MET-hours/week). In low urbanicity areas, the association between income and total PA went from negative in 1991 (p < 0.05) to positive by 2000 (p < 0.05). In relatively high urbanicity areas, the income-PA relationship was positive at all time points and was statistically significant at most time points after 1997 (p < 0.05). Leisure PA was the only domain of PA that increased over time, but >95% of individuals in low urbanicity areas reported zero leisure PA at each time point. CONCLUSIONS: Our findings show changing associations for income and urbanicity with PA over 18 years of urbanization. Total PA was lower for individuals living in more versus less urban areas at all time points. However, these differences narrowed over time, which may relate to increases in individual-level income in less urban areas of China with urbanization. Low-income individuals in higher urbanicity areas are a particularly critical group to target to increase PA in China.

Associations between age, cohort, and urbanization with SBP and DBP in China: a population-based study across 18 years.

OBJECTIVE: Little is known about whether large-scale environmental changes, such as those seen with urbanization, are differentially associated with SBP versus DBP, and whether those changes vary by birth cohort. METHODS: We used data from the China Health and Nutrition Survey, a population-based cohort study of Chinese adults (n = 18 754 aged 18-70 years), seen a maximum of seven times from 1991 to 2009. We used hierarchical multivariable linear models to simultaneously estimate SBP and DBP as correlated outcomes over time, accounting for their physiologic, time-varying correlation. Main exposure variables were urbanicity, age, and birth cohort. Over 18 years of modernization, median SBP and DBP increased by 10 and 7 mmHg, respectively. RESULTS: Our hierarchical model results suggest greater temporal increases in SBP and particularly DBP at lower versus higher urbanicity. At the same chronological age, for a 10-year difference in birth cohort (i.e. born in 1980s versus 1970s), the adjusted mean DBP was approximately 3 mmHg higher for the later birth cohort (P < 0.001). Pulse pressure (calculated as model-predicted SBP minus DBP) was also higher at low versus high urbanicity. CONCLUSIONS: These results suggest increased susceptibility of DBP (and thus peripheral vascular resistance) to environmental change, particularly in younger Chinese adults. Because DBP more strongly predicts cardiovascular disease risk in younger adulthood, hypertension-related health burden in China may increase over time.

Longitudinal trajectories of BMI and cardiovascular disease risk: the national longitudinal study of adolescent health.

OBJECTIVE: In adulthood, excess BMI is associated with cardiovascular disease (CVD); it is unknown whether risk differs by BMI trajectories from adolescence to adulthood. DESIGN AND METHODS: The National Longitudinal Study of Adolescent Health, a nationally representative, longitudinal adolescent cohort (mean age: 16.9 years) followed into adulthood (mean age: 28.8 years) [n = 13,984 individuals (41,982 observations)] was examined. Separate logistic regression models for diabetes, hypertension, and inflammation were used to examine odds of risk factors at given adult BMI according to varying BMI trajectories from adolescence to adulthood. RESULTS: CVD risk factor prevalence at follow-up ranged from 5.5% (diabetes) to 26.4% (hypertension) and 31.3% (inflammation); risk differed across BMI trajectories. For example, relative to men aged 27 years (BMI = 23 kg/m(2) maintained over full study period), odds for diabetes were comparatively higher for men of the same age and BMI ≈ 30 kg/m(2) with ≈8 BMI unit gain between 15 and 20 years (OR = 2.35; 95% CI, 1.51, 3.66) or in those who maintained BMI ≈ 30 kg/m(2) across the study period (OR = 2.33; 1.92, 2.83) relative to the same ≈8 BMI unit gain, but between 20 and 27 years (OR = 1.44; 1.10, 1.87). CONCLUSIONS: Specific periods and patterns of weight gain in the transition from adolescence to adulthood might be critical for CVD preventive efforts.