Quynh C. Nguyen

The role of health insurance in explaining immigrant versus non-immigrant disparities in access to health care: Comparing the United States to Canada

Using a cross-national comparative approach, we examined the influence of health insurance on U.S. immigrant versus non-immigrant disparities in access to primary health care. With data from the 2002/2003 Joint Canada/United States Survey of Health, we gathered evidence using three approaches: 1) we compared health care access among insured and uninsured immigrants and non-immigrants within the U.S.; 2) we contrasted these results with health care access disparities between immigrants and non-immigrants in Canada, a country with universal health care; and 3) we conducted a novel direct comparison of health care access among insured and uninsured U.S. immigrants with Canadian immigrants (all of whom are insured). Outcomes investigated were self-reported unmet medical needs and lack of a regular doctor. Logistic regression models controlled for age, sex, nonwhite status, marital status, education, employment, and self-rated health. In the U.S., odds of unmet medical needs of insured immigrants were similar to those of insured non-immigrants but far greater for uninsured immigrants. The effect of health insurance was even more striking for lack of regular doctor. Within Canada, disparities between immigrants and non-immigrants were similar in magnitude to disparities seen among insured Americans. For both outcomes, direct comparisons of U.S. and Canada revealed significant differences between uninsured American immigrants and Canadian immigrants, but not between insured Americans and Canadians, stratified by nativity. Findings suggest health care insurance is a critical cause of differences between immigrants and non-immigrants in access to primary care, lending robust support for the expansion of health insurance coverage in the U.S. This study also highlights the usefulness of cross-national comparisons for establishing alternative counterfactuals in studies of disparities in health and health care.

Discordance in National Estimates of Hypertension Among Young Adults

Background: In the United States, where coronary heart disease (CHD) is the leading cause of mortality, CHD risk assessment is a priority and accurate blood pressure (BP) measurement is essential. Methods: Hypertension estimates in the National Longitudinal Study of Adolescent Health (Add Health), Wave IV (2008)—a nationally representative field study of 15,701 participants aged 24–32—was referenced against NHANES (2007–2008) participants of the same age. We examined discordances in hypertension, and estimated the accuracy and reliability of blood pressure in the Add Health study. Results: Hypertension rates (BP: ≥140/90 mm Hg) were higher in Add Health compared with NHANES (19% vs. 4%), but self-reported history was similar (11% vs. 9%) among adults aged 24–32. Survey weights and adjustments for differences in participant characteristics, examination time, use of antihypertensive medications, and consumption of food/caffeine/cigarettes before blood pressure measurement had little effect on between-study differences in hypertension estimates. Among Add Health participants interviewed and examined twice (full and abbreviated interviews), blood pressure was similar, as was blood pressure at the in-home and in-clinic examinations conducted by NHANES III (1988–1994). In Add Health, there was minimal digit preference in blood pressure measurements; mean bias never exceeded 2 mm Hg; and reliability (estimated as intraclass correlation coefficients) was 0.81 and 0.68 for systolic and diastolic BPs, respectively. Conclusions: The proportion of young adults in NHANES reporting a history of hypertension was twice that with measured hypertension, whereas the reverse was found in Add Health. Between-survey differences were not explained by digit preference, low validity, or reliability of Add Health blood pressure data, or by salient differences in participant selection, measurement context, or interview content. The prevalence of hypertension among Add Health Wave IV participants suggests an unexpectedly high risk of cardiovascular disease among US young adults and warrants further scrutiny.

Practical Guidance for Conducting Mediation Analysis With Multiple Mediators Using Inverse Odds Ratio Weighting

Despite the recent flourishing of mediation analysis techniques, many modern approaches are difficult to implement or applicable to only a restricted range of regression models. This report provides practical guidance for implementing a new technique utilizing inverse odds ratio weighting (IORW) to estimate natural direct and indirect effects for mediation analyses. IORW takes advantage of the odds ratios invariance property and condenses information on the odds ratio for the relationship between the exposure (treatment) and multiple mediators, conditional on covariates, by regressing exposure on mediators and covariates. The inverse of the covariate-adjusted exposure-mediator odds ratio association is used to weight the primary analytical regression of the outcome on treatment. The treatment coefficient in such a weighted regression estimates the natural direct effect of treatment on the outcome, and indirect effects are identified by subtracting direct effects from total effects. Weighting renders treatment and mediators independent, thereby deactivating indirect pathways of the mediators. This new mediation technique accommodates multiple discrete or continuous mediators. IORW is easily implemented and is appropriate for any standard regression model, including quantile regression and survival analysis. An empirical example is given using data from the Moving to Opportunity (1994-2002) experiment, testing whether neighborhood context mediated the effects of a housing voucher program on obesity. Relevant Stata code (StataCorp LP, College Station, Texas) is provided.

A cross-national comparative perspective on racial inequities in health: the USA versus Canada

Background: Cross-national comparisons allow the examination of the malleability of associations between race and health. Racial inequities in chronic conditions, indicators of health status and behavioural risk factors between two similar advanced capitalist countries were compared. It was hypothesised that racial inequities will be mitigated in Canada compared with the USA. Methods: Population-based, cross-sectional data from the 2002–3 Joint Canada–USA Survey of Health (JCUSH) with 4953 adult respondents from the USA and 3455 from Canada. Models adjusted for age, sex, foreign birth, marital status, health insurance, education, income and home ownership. Results: Compared with the USA, racial inequities in health were attenuated in Canada. In the USA, racial inequities in chronic diseases and fair or poor self-rated health were largely driven by inequities found among the native born. Strikingly, in Canada, however, there were few significant racial inequities and those occurred exclusively among the foreign born. Within strata of race and foreign birth, Canadians fared better, with both white people and non-white people reporting better health than their American counterparts. Foreign-born Canadians and Americans were more similar to each other in terms of health than native-born Canadians and Americans. Only among the native born did American white people and American non-white people have higher adjusted odds of hypertension, diabetes and obesity than Canadian white people and Canadian non-white people respectively. Self-rated health was worse for non-white Americans than non-white Canadians regardless of foreign birth. Conclusion: The influence of race on health is context dependent. There is no necessary link between race and a variety of health indicators.

Adolescent expectations of early death predict young adult socioeconomic status

Among adolescents, expectations of early death have been linked to future risk behaviors. These expectations may also reduce personal investment in education and training, thereby lowering adult socioeconomic status attainment. The importance of socioeconomic status is highlighted by pervasive health inequities and dramatic differences in life expectancy among education and income groups. The objectives of this study were to investigate patterns of change in perceived chances of living to age 35 (Perceived Survival Expectations; PSE), predictors of PSE, and associations between PSE and future socioeconomic status attainment. We utilized the U.S. National Longitudinal Study of Adolescent Health (Add Health) initiated in 1994-1995 among 20,745 adolescents in grades 7-12 with follow-up interviews in 1996 (Wave II), 2001-2002 (Wave III) and 2008 (Wave IV; ages 24-32). At Wave I, 14% reported ≤50% chance of living to age 35 and older adolescents reported lower PSE than younger adolescents. At Wave III, PSE were similar across age. Changes in PSE from Wave I to III were moderate, with 89% of respondents reporting no change (56%), one level higher (22%) or one level lower (10%) in a 5-level PSE variable. Higher block group poverty rate, perceptions that the neighborhood is unsafe, and less time in the U.S. (among the foreign-born) were related to low PSE at Waves I and III. Low PSE at Waves I and III predicted lower education attainment and personal earnings at Wave IV in multinomial logistic regression models controlling for confounding factors such as previous family socioeconomic status, individual demographic characteristics, and depressive symptoms. Anticipation of an early death is prevalent among adolescents and predictive of lower future socioeconomic status. Low PSE reported early in life may be a marker for worse health trajectories.

Leveraging geotagged Twitter data to examine neighborhood happiness, diet, and physical activity

OBJECTIVES Using publicly available, geotagged Twitter data, we created neighborhood indicators for happiness, food and physical activity for three large counties: Salt Lake, San Francisco and New York. METHODS We utilize 2.8 million tweets collected between February-August 2015 in our analysis. Geo-coordinates of where tweets were sent allow us to spatially join them to 2010 census tract locations. We implemented quality control checks and tested associations between Twitter-derived variables and sociodemographic characteristics. RESULTS For a random subset of tweets, manually labeled tweets and algorithm labeled tweets had excellent levels of agreement: 73% for happiness; 83% for food, and 85% for physical activity. Happy tweets, healthy food references, and physical activity references were less frequent in census tracts with greater economic disadvantage and higher proportions of racial/ethnic minorities and youths. CONCLUSIONS Social media can be leveraged to provide greater understanding of the well-being and health behaviors of communities-information that has been previously difficult and expensive to obtain consistently across geographies. More open access neighborhood data can enable better design of programs and policies addressing social determinants of health.

Societal context and the production of immigrant status-based health inequalities: A comparative study of the United States and Canada

Background: We compare disparities in health status between first-generation immigrants and others in the United States (US) and Canada. Methods: We used data from the Joint Canada–US Survey of Health. The regression models adjusted for demographics, socioeconomic status, and health insurance (the US). Results: In both countries, the health advantage belonged to immigrants. Fewer disparities between immigrants and those native-born were seen in Canada versus the US. Canadians of every immigrant/race group fared better than US native-born Whites. Discussion: Fewer disparities in Canada and better overall health of all Canadians suggest that societal context may create differences in access to the resources, environments, and experiences that shape health and health behaviors.

Adolescent Expectations of Early Death Predict Adult Risk Behaviors

Only a handful of public health studies have investigated expectations of early death among adolescents. Associations have been found between these expectations and risk behaviors in adolescence. However, these beliefs may not only predict worse adolescent outcomes, but worse trajectories in health with ties to negative outcomes that endure into young adulthood. The objectives of this study were to investigate perceived chances of living to age 35 (Perceived Survival Expectations, PSE) as a predictor of suicidal ideation, suicide attempt and substance use in young adulthood. We examined the predictive capacity of PSE on future suicidal ideation/attempt after accounting for sociodemographics, depressive symptoms, and history of suicide among family and friends to more fully assess its unique contribution to suicide risk. We investigated the influence of PSE on legal and illegal substance use and varying levels of substance use. We utilized the National Longitudinal Study of Adolescent Health (Add Health) initiated in 1994–95 among 20,745 adolescents in grades 7–12 with follow-up interviews in 1996 (Wave II), 2001–02 (Wave III) and 2008 (Wave IV; ages 24–32). Compared to those who were almost certain of living to age 35, perceiving a 50–50 or less chance of living to age 35 at Waves I or III predicted suicide attempt and ideation as well as regular substance use (i.e., exceeding daily limits for moderate drinking; smoking ≥ a pack/day; and using illicit substances other than marijuana at least weekly) at Wave IV. Associations between PSE and detrimental adult outcomes were particularly strong for those reporting persistently low PSE at both Waves I and III. Low PSE at Wave I or Wave III was also related to a doubling and tripling, respectively, of death rates in young adulthood. Long-term and wide-ranging ties between PSE and detrimental outcomes suggest these expectations may contribute to identifying at-risk youth.

Racial Disparities in Access to Care Under Conditions of Universal Coverage

BACKGROUND Racial disparities in access to regular health care have been reported in the U.S., but little is known about the extent of disparities in societies with universal coverage. PURPOSE To investigate the extent of racial disparities in access to care under conditions of universal coverage by observing the association between race and regular access to a doctor in Canada. METHODS Racial disparities in access to a regular doctor were calculated using the largest available source of nationally representative data in Canada--the Canadian Community Health Survey. Surveys from 2000-2010 were analyzed in 2014. Multinomial regression analyses predicted odds of having a regular doctor for each racial group compared to whites. Analyses were stratified by immigrant status--Canadian-born versus shorter-term immigrant versus longer-term immigrants--and controlled for sociodemographics and self-rated health. RESULTS Racial disparities in Canada, a country with universal coverage, were far more muted than those previously reported in the U.S. Only among longer-term Latin American immigrants (OR=1.90, 95% CI=1.45, 2.08) and Canadian-born Aboriginals (OR=1.34, 95% CI=1.22, 1.47) were significant disparities noted. Among shorter-term immigrants, all Asians were more likely than whites, and among longer-term immigrants, South Asians were more like than whites, to have a regular doctor. CONCLUSIONS Universal coverage may have a major impact on reducing racial disparities in access to health care, although among some subgroups, other factors may also play a role above and beyond health insurance.

Were the mental health benefits of a housing mobility intervention larger for adolescents in higher socioeconomic status families

Moving to Opportunity (MTO) was a social experiment to test how relocation to lower poverty neighborhoods influences low-income families. Using adolescent data from 4 to 7 year evaluations (aged 12-19, n=2829), we applied gender-stratified intent-to-treat and adherence-adjusted linear regression models, to test effect modification of MTO intervention effects on adolescent mental health. Low parental education, welfare receipt, unemployment and never-married status were not significant effect modifiers. Tailoring mobility interventions by these characteristics may not be necessary to alter impact on adolescent mental health. Because parental enrollment in school and teen parent status adversely modified MTO intervention effects on youth mental health, post-move services that increase guidance and supervision of adolescents may help support post-move adjustment.