Tony Tam

Divergent Urban-Rural Trends in College Attendance: State Policy Bias and Structural Exclusion in China.

Despite the massive expansion of higher education in China since 1998, the cohort trends of urban and rural hukou holders in college attendance have widened sharply. Prevailing explanations emphasize the advantages of urban students over rural students in school quality and household financial resources. We propose the structural exclusion hypothesis that underscores the unintended consequences of a state policy: the urban concentrated expansion of vocational upper secondary education. This policy makes the expanding opportunity inaccessible for most rural students but helps lower-achieving urban students remain in the “pipeline” for college. We conduct a crucial test of these explanations by linking provincial-level enrollment statistics with individual-level models of the urban-rural trends in college attendance. The data are drawn from the 2006 Chinese General Social Survey and official statistics for 28 college admission districts over 14 college admission cohorts (1989-2002). Findings suggest that the rising urban advantage originates from the virtually exclusive increase in opportunities for vocational education among urban students. As vocational education is mainly an option for lower-achieving students, the expansion of vocational education most benefits lower-achieving urban students. The widening differences between urban and rural hukou in college attendance therefore reflects the advantage given “marginal” urban students in access to vocational schools.

Satellite-based estimates of long-term exposure to fine particulate matter are associated with C-reactive protein in 30 034 Taiwanese adults

Abstract Background Particulate matter (PM) air pollution is associated with the risk of cardiovascular morbidity and mortality. However, the biological mechanism underlying the associations remains unclear. Atherosclerosis, the underlying pathology of cardiovascular disease, is a chronic inflammatory process. We therefore investigated the association of long-term exposure to fine PM (PM2.5) with C-reactive protein (CRP), a sensitive marker of systemic inflammation, in a large Taiwanese population. Methods Participants were from a large cohort who participated in a standard medical examination programme with measurements of high-sensitivity CRP between 2007 and 2014. We used a spatiotemporal model to estimate 2-year average PM2.5 exposure at each participant’s address, based on satellite-derived aerosol optical depth data. General regression models were used for baseline data analysis and mixed-effects linear regression models were used for repeated data analysis to investigate the associations between PM2.5 exposure and CRP, adjusting for a wide range of potential confounders. Results In this population of 30 034 participants with 39 096 measurements, every 5 μg/m3 PM2.5 increment was associated with a 1.31% increase in CRP [95% confidence interval (CI): 1.00%, 1.63%) after adjusting for confounders. For those participants with repeated CRP measurements, no significant changes were observed between the first and last measurements (0.88 mg/l vs 0.89 mg/l, P = 0.337). The PM2.5 concentrations remained stable over time between 2007 and 2014. Conclusions Long-term exposure to PM2.5 is associated with increased level of systemic inflammation, supporting the biological link between PM2.5 air pollution and deteriorating cardiovascular health. Air pollution reduction should be an important strategy to prevent cardiovascular disease.

The Making of Higher Education Inequality: How Do Mechanisms and Pathways Depend on Competition?

We extend the theoretical contributions of Alon (2009) by proposing and testing two hypotheses about the context dependence of inequality of educational opportunity (IEO). Alon offers a model of IEO that incorporates class adaptation and organizational exclusion as two test-score-based mechanisms that perpetuate class inequality. She hypothesizes that the changing level of IEO depends on trends in competition. Through a secondary analysis of Alon’s numerical results, we clarify her results and demonstrate that the causal structure of IEO (e.g., the explanatory roles of adaptation and exclusion) depends on trends in competition and college selectivity. Additionally, changes in competition for college admission from 1972 to 1992 had little to do with enrollment rates, but appear to be driven largely by changes in college wage premiums.

Particulate matter air pollution, physical activity and systemic inflammation in Taiwanese adults

BACKGROUND The protective effects of physical activity (PA) against chronic disease can be partially ascribed to its anti-inflammatory effects. On the other hand, long-term exposure to particulate matter with an aerodynamic diameter less than 2.5μm (PM2.5) may induce systemic inflammation. OBJECTIVE To investigate the joint effects of habitual PA and long-term exposure to PM2.5 on systemic inflammation in a large cohort of Taiwanese adults. METHODS We studied 359,067 adult participants from a cohort consisting of Taiwanese residents who participated in a standard medical examination program from 2001 to 2014. Peripheral white blood cell (WBC) and differential counts were measured as indicators of systemic inflammation. Two-year average concentration of PM2.5 was estimated at each participants address using a satellite-based spatio-temporal model. Habitual PA level was assessed by questionnaire (inactive, low, moderate and high). Mixed-effects linear regression model was used to examine the associations of WBC counts with PM2.5 and PA. RESULTS Compared with inactive participants, those with low, moderate or high PA levels had 0.36% [95% confidence interval (CI): 0.31%, 0.41%], 0.70% (95%CI: 0.65%, 0.76%) and 1.16% (95%CI: 1.11%, 1.22%) lower WBC counts, respectively, after adjusting for PM2.5 exposure and a wide range of confounders. Long-term PM2.5 exposure was associated with increased WBC counts at all PA levels. Analyses for differential counts generated similar results. No significant interaction was observed between PA and PM2.5 exposure (P for interaction=0.59). CONCLUSIONS Habitual PA was associated with statistically significant lower markers of systemic inflammation across different levels of PM2.5. Effects of PA and PM2.5 exposure on systemic inflammation are independent.

Age, gender, and socioeconomic gradients in metabolic syndrome: biomarker evidence from a large sample in Taiwan, 2005–2013

PURPOSE To examine the age and gender heterogeneities in the association between socioeconomic status (SES) and the risk of metabolic syndrome (MetS) with biomarker data from Taiwan. METHODS Subjects included 102,201 men and 112,015 women aged 25 and above, from the 2005-2013 MJ Health Survey in Taiwan. SES was measured by education and family income. MetS was defined by the Adult Treatment Panel III criteria for Asian population. Logistic regression analyses were performed by age and gender groups. RESULTS (1) Higher education level was associated with significantly lower risk of MetS. (2) Higher income was associated with lower MetS risk among women aged under 65, but no association among men of all ages. (3) SES gradients were generally much stronger among women than among men of the same age group. (4) SES gradients reduced over the life course with the exception that income gradient remains flat among men of all ages. CONCLUSIONS Among Chinese in Taiwan, the gender and age heterogeneities in the SES gradients in MetS are similar to those reported for Western societies. This cross-cultural convergence is broadly consistent with the general hypothesis that social conditions are fundamental causes of diseases and health disparities.

Effect of long-term exposure to fine particulate matter on lung function decline and risk of chronic obstructive pulmonary disease in Taiwan: a longitudinal, cohort study

BACKGROUND Information on the effects of long-term exposure to fine particulate matter with an aerodynamic diameter of 2·5 μm or less (PM2·5) on lung health is scarce. We aimed to investigate the associations between long-term exposure to PM2·5, lung function, and chronic obstructive pulmonary disease (COPD) in a large-scale longitudinal cohort. METHODS We included 285 046 participants aged 20 years or older from the Taiwan MJ Health Management Institution cohort, who were recruited between 2001 and 2014 and had spirometric tests during the medical examination visit. We used a satellite-based spatiotemporal model to estimate the 2-year average ground concentration of PM2·5 (for the calendar year of each participants medical examination and for the previous year) at each participants address. We used the generalised linear mixed model to examine the associations between PM2·5 concentrations and lung function and the Cox proportional hazard regression model with time-dependent covariates to investigate the PM2·5 effects on COPD development. FINDINGS Every 5 μg/m3 increment in PM2·5 was associated with a decrease of 1·18% for forced vital capacity (FVC), 1·46% for forced expiratory volume in 1 s (FEV1), 1·65% for maximum mid-expiratory flow (MMEF), and 0·21% for FEV1:FVC ratio. The decrease accelerated over time. Additional annual declines were observed for FVC (0·14%), FEV1 (0·24%), MMEF (0·44%), and FEV1:FVC ratio (0·09%). Compared with the participants exposed to the first quartile of PM2·5, participants exposed to the fourth, third, and second quartiles of PM2·5 had a hazard ratio of 1·23 (95% CI 1·09-1·39), 1·30 (1·16-1·46), and 1·39 (1·24-1·56) for COPD development, respectively. INTERPRETATION Long-term exposure to ambient PM2·5 is associated with reduced, and faster declines in, lung function. Long-term exposure to ambient PM2·5 is also associated with an increased risk of the incidence of COPD. This study reinforces the urgency of global strategies to mitigate air pollution for improvement of pulmonary health and prevention of COPD. FUNDING Environmental Health Research Fund of the Chinese University of Hong Kong and PhD Studentship of the Chinese University of Hong Kong.

Exposure to ambient fine particulate matter and semen quality in Taiwan

Objectives Environmental exposure to chemicals has been considered a potential factor contributing to deteriorated semen quality. However, previous literature on exposure to air pollution and semen quality is inconsistent. We therefore investigated the health effects of short-term and long-term exposure to fine particulate matter (PM2.5) on semen quality in Taiwanese men from the general population. Methods A cross-sectional study was conducted among 6475 male participants aged 15–49 years who participated in a standard medical examination programme in Taiwan between 2001 and 2014. Semen quality was assessed according to the WHO 1999 guidelines, including sperm concentration, total motility, progressive motility and morphology. Three-month and 2-year average PM2.5 concentrations were estimated at each participant’s address using a spatiotemporal model based on satellite-derived aerosol optical depth data. Multivariable linear and logistic regressions were used to examine the associations between PM2.5 and semen quality. Results A robust association was observed between exposure to PM2.5 and decreased normal morphology. Every increment of 5 µg/m3 in 2-year average PM2.5 was significantly associated with a decrease of 1.29% in sperm normal morphology and a 26% increased risk of having the bottom 10% of sperm normal morphology, after adjusting for a wide range of potential confounders (p<0.001). On the other hand, an increment of 5 µg/m3 in 2-year average PM2.5 was associated with an increase of 1.03×106/mL in sperm concentration and a 10% decreased risk of being the bottom 10% of sperm concentration (both p<0.001). Similar results were found for 3-month PM2.5. Conclusions Exposure to ambient PM2.5 air pollution is associated with a lower level of sperm normal morphology and a higher level of sperm concentration.

Long-term exposure to ambient particulate matter (PM2.5) is associated with platelet counts in adults

BACKGROUND The prothrombotic effects of particulate matter (PM) may underlie the association of air pollution with increased risks of cardiovascular disease. This study aimed to investigate the association between long-term exposure to PM with an aerodynamic diameter ≤2.5 μm (PM2.5) and platelet counts, a marker of coagulation profiles. METHODS The study participants were from a cohort consisting of 362,396 Taiwanese adults who participated in a standard medical examination program between 2001 and 2014. Platelet counts were measured through Complete Blood Count tests. A satellite-based spatio-temporal model was used to estimate 2-year average ambient PM2.5 concentration at each participants address. Mixed-effects linear regression models were used to investigate the association between PM2.5 exposure and platelet counts. RESULTS This analysis included 175,959 men with 396,248 observations and 186,437 women with 397,877 observations. Every 10-μg/m3 increment in the 2-year average PM2.5 was associated with increases of 0.42% (95% CI: 0.38%, 0.47%) and 0.49% (95% CI: 0.44%, 0.54%) in platelet counts in men and women, respectively. A series of sensitivity analyses, including an analysis in participants free of cardiometabolic disorders, confirmed the robustness of the observed associations. Baseline data analyses showed that every 10-μg/m3 increment in PM2.5 was associated with higher risk of 17% and 14% of having elevated platelet counts (≥90th percentile) in men and women, respectively. CONCLUSIONS Long-term exposure to PM2.5 appears to be associated with increased platelet counts, indicating potential adverse effects on blood coagulability.

Increased leisure-time physical activity associated with lower onset of diabetes in 44 828 adults with impaired fasting glucose: a population-based prospective cohort study.

Aims To evaluate the effects of habitual leisure-time physical activity (LTPA) on incident type 2 diabetes in a prospective cohort of Chinese adults with impaired fasting glucose (IFG). Methods 44 828 Chinese adults aged 20–80 years with newly detected IFG but free from cardiovascular and cerebrovascular disease were recruited and followed up from 1996 to 2014. Incident type 2 diabetes was identified by fasting plasma glucose ≥7 mmol/L. The participants were classified into four categories based on their self-reported weekly LTPA: inactive, low, moderate, or high. Hazard ratios (HRs) and population attributable fractions (PAFs) were estimated with adjustment for established diabetic risk factor. Results After 214 148 person-years of follow-up, we observed an inverse dose–response relationship between LTPA and diabetes risk. Compared with inactive participants, diabetes risk in individuals reporting low, moderate and high volume LTPA were reduced by 12% (HR 0.88, 95% CI 0.80 to 0.99; P=0.015), 20% (HR 0.80, 95% CI 0.71 to 0.90; P<0.001), and 25% (HR 0.75, 95% CI 0.67 to 0.83; P<0.001), respectively. At least 19.2% (PAF 19.2%, 95% CI 5.9% to 30.6%) of incident diabetes cases could be avoided if the inactive participants had engaged in WHO recommendation levels of LTPA. This would correspond to a potential reduction of at least 7 million diabetic patients in the Greater China area. Conclusions Our results show higher levels of LTPA are associated with a lower risk of diabetes in IFG subjects. These data emphasise the urgent need for promoting physical activity as a preventive strategy against diabetes to offset the impact of population ageing and the growing obesity epidemic.

Academic achievement as status competition: Intergenerational transmission of positional advantage among Taiwanese and American students

This article compares the intergenerational transmission of relative/positional advantage for the academic achievement of secondary school students in Taiwan and the USA. Although any monotonic transformation of rank order is a valid measure of positional status, we use ‘the average number of competitors excluded’ as the index of positional status (PSI) because it is a ratio-scale metric easy to interpret and universally comparable—even among different variables and achievement test scores based on completely different tests. A PSI analysis of two large-scale national surveys of secondary school students (TEPS and NELS) shows that parental education plays a much stronger role than family income in both societies. Most important, parental education and income effects on the PSI are statistically indistinguishable between the two societies, despite very substantial differences in the institution of secondary education, including the screening and allocation of secondary students for higher education. This resemblance is especially striking given the large cross-national variation in the same PSI-based measures of intergenerational transmission of positional advantage among Organisation for Economic Co-operation and Development (OECD) countries.