Misstatements, misperceptions, and mistakes in controlling for covariates in observational research.

We discuss 12 misperceptions, misstatements, or mistakes concerning the use of covariates in observational or nonrandomized research. Additionally, we offer advice to help investigators, editors, reviewers, and readers make more informed decisions about conducting and interpreting research where the influence of covariates may be at issue. We primarily address misperceptions in the context of statistical management of the covariates through various forms of modeling, although we also emphasize design and model or variable selection. Other approaches to addressing the effects of covariates, including matching, have logical extensions from what we discuss here but are not dwelled upon heavily. The misperceptions, misstatements, or mistakes we discuss include accurate representation of covariates, effects of measurement error, overreliance on covariate categorization, underestimation of power loss when controlling for covariates, misinterpretation of significance in statistical models, and misconceptions about confounding variables, selecting on a collider, and p value interpretations in covariate-inclusive analyses. This condensed overview serves to correct common errors and improve research quality in general and in nutrition research specifically.

Emollients for preventing atopic eczema: Cost-effectiveness analysis of the BEEP trial.

BACKGROUND: Recent discoveries have led to the suggestion that enhancing skin barrier from birth might prevent eczema and food allergy. OBJECTIVE: To determine the cost-effectiveness of daily all-over-body application of emollient during the first year of life for preventing atopic eczema in high-risk children at 2 years from a health service perspective. We also considered a 5-year time horizon as a sensitivity analysis. METHODS: A within-trial economic evaluation using data on health resource use and quality of life captured as part of the BEEP trial alongside the trial data. Parents/carers of 1394 infants born to families at high risk of atopic disease were randomised 1:1 to the emollient group, which were advised to apply emollient (Doublebase Gel or Diprobase Cream) to their child at least once daily to the whole body during the first year of life or usual care. Both groups received advice on general skin care. The main economic outcomes were incremental cost-effectiveness ratio (ICER), defined as incremental cost per percentage decrease in risk of eczema in the primary cost-effectiveness analysis. Secondary analysis, undertaken as a cost-utility analysis, reports incremental cost per Quality-Adjusted Life Year (QALY) where child utility was elicited using the proxy CHU-9D at 2 years. RESULTS: At 2 years, the adjusted incremental cost was £87.45 (95% CI -54.31, 229.27) per participant, whilst the adjusted proportion without eczema was 0.0164 (95% CI -0.0329, 0.0656). The ICER was £5337 per percentage decrease in risk of eczema. Adjusted incremental QALYs were very slightly improved in the emollient group, 0.0010 (95% CI -0.0069, 0.0089). At 5 years, adjusted incremental costs were lower for the emollient group, -£106.89 (95% CI -354.66, 140.88) and the proportion without eczema was -0.0329 (95% CI -0.0659, 0.0002). The 5-year ICER was £3201 per percentage decrease in risk of eczema. However, when inpatient costs due to wheezing were excluded, incremental costs were lower and incremental effects greater in the usual care group. CONCLUSIONS: In line with effectiveness endpoints, advice given in the BEEP trial to apply daily emollient during infancy for eczema prevention in high-risk children does not appear cost-effective.

Evaluation of Unintended Consequences of COVID-19 Pandemic Restrictions and Obesity Prevalence Among Youths.

This cohort study examines the association between COVID-19 pandemic restrictions and obesity prevalence among youths aged 2 to 19 years in Monroe County, Indiana.

Healthcare expenditure and its socio-demographic and clinical predictors in Australians with poorly controlled asthma.

INTRODUCTION: Asthma has substantial and increasing health and economic burden worldwide. This study aimed to estimate healthcare expenditure and determine the factors that increase expenditure in Australians with poorly controlled asthma. METHODS: Individuals ≥18 years of age with poorly controlled asthma, as determined by a score ≥1.5 on the Asthma Control Questionnaire, were included in the study. Healthcare utilization costs from medical services and medications were estimated over an average follow-up of 12 months from administratively linked data: the Medicare Benefits Schedule and Pharmaceutical Benefits Scheme. A generalized linear model with gamma distribution and log link was used to predict participants' key baseline characteristics associated with variations in healthcare costs. RESULTS: A total of 341 participants recruited through community pharmacies were included. The mean (standard deviation, SD) age of participants was 56.6 (SD 17.6) years, and approximately 71% were females. The adjusted average monthly healthcare expenditure per participant was $AU386 (95% CI: 336, 436). On top of the average monthly costs, an incremental expenditure was found for each year increase in age ($AU4; 95% CI: 0.78, 7), being unemployed ($AU201; 95% CI: 91, 311), one unit change in worsening quality of life ($AU35; 95% CI: 9, 61) and being diagnosed with depression and anxiety ($AU171; 95% CI: 36, 306). CONCLUSIONS: In a cohort of Australian patients, characterized by poor asthma control and co-morbidities individuals impose substantial economic burden in terms of Medicare funded medical services and medications. Programs addressing strategies to improve the quality of life and manage co-morbid anxiety and depression and encourage asthma patients' engagement in clinically tolerable jobs, may result in significant cost savings to the health system.

Emollients for prevention of atopic dermatitis: 5-year findings from the BEEP randomized trial.

BACKGROUND: The effectiveness of emollients for preventing atopic dermatitis/eczema is controversial. The Barrier Enhancement for Eczema Prevention trial evaluated the effects of daily emollients during the first year of life on atopic dermatitis and atopic conditions to age 5 years. METHODS: 1394 term infants with a family history of atopic disease were randomized (1:1) to daily emollient plus standard skin-care advice (693 emollient group) or standard skin-care advice alone (701 controls). Long-term follow-up at ages 3, 4 and 5 years was via parental questionnaires. Main outcomes were parental report of a clinical diagnosis of atopic dermatitis and food allergy. RESULTS: Parents reported more frequent moisturizer application in the emollient group through to 5 years. A clinical diagnosis of atopic dermatitis between 12 and 60 months was reported for 188/608 (31%) in the emollient group and 178/631 (28%) in the control group (adjusted relative risk 1.10, 95% confidence interval 0.93 to 1.30). Although more parents in the emollient group reported food reactions in the previous year at 3 and 4 years, cumulative incidence of doctor-diagnosed food allergy by 5 years was similar between groups (92/609 [15%] emollients and 87/632 [14%] controls, adjusted relative risk 1.11, 95% confidence interval 0.84 to 1.45). Findings were similar for cumulative incidence of asthma and hay fever. CONCLUSIONS: Daily emollient application during the first year of life does not prevent atopic dermatitis, food allergy, asthma or hay fever.

Willing or Hesitant? A Socioeconomic Study on the Potential Acceptance of COVID-19 Vaccine in Japan.

The worldwide COVID-19 vaccination program is already underway, raising hopes and aspirations to contain the spread of the COVID-19 pandemic that halted economic and social activities. However, the issue of vaccine effectiveness and its side-effects is influencing the potential acceptance of vaccines. In this uncertain situation, we used data from a nationwide survey in Japan during February 2021, following the Japanese government's initial phase of COVID-19 vaccination. Our results show that 47% of the respondents are willing to take a vaccine once it is available, while 22% are not willing and another 31% remain indecisive. Our ordered probit regression results show that demographic, socioeconomic, and behavioral variables such as gender, age, subjective health status, children, household income, household assets, financial literacy, future anxiety, and myopic view of the future are associated with willingness to take a COVID-19 vaccine. Our findings suggest that Japan's government should not adopt a one-size-fits-all policy to promote the vaccination program, but rather target people with specific socioeconomic backgrounds who are less willing and more hesitant to take a vaccine.

Measuring Hypertension Progression With Transition Probabilities: Estimates From the WHO SAGE Longitudinal Study.

This paper assessed the transition probabilities between the stages of hypertension severity and the length of time an individual might spend at a particular disease state using the new American College of Cardiology/American Heart Association hypertension blood pressure guidelines. Data for this study were drawn from the Ghana WHO SAGE longitudinal study, with an analytical sample of 1884 across two waves. Using a multistate Markov model, we estimated a seven-year transition probability between normal/elevated blood pressure (systolic ≤ 129 mm Hg & diastolic <80 mm Hg), stage 1 (systolic 130-139 mm Hg & diastolic 80-89 mm Hg), and stage 2 (systolic ≥140mm Hg & diastolic≥90 mm Hg) hypertension and adjusted for the individual effects of anthropometric, lifestyle, and socio-demographic factors. At baseline, 22.5% had stage 1 hypertension and 52.2% had stage 2 hypertension. The estimated seven-year transition probability for the general population was 19.0% (95% CI: 16.4, 21.8) from normal/elevated blood pressure to stage 1 hypertension, 31.6% (95% CI: 27.6, 35.4%) from stage 1 hypertension to stage 2 hypertension, and 48.5% (45.6, 52.1%) for remaining at stage 2. Other factors such as being overweight, obese, female, aged 60+ years, urban residence, low education and high income were associated with an increased probability of remaining at stage 2 hypertension. However, consumption of recommended servings of fruits and vegetables per day was associated with a delay in the onset of stage 1 hypertension and a recovery to normal/elevated blood pressure. This is the first study to show estimated transition probabilities between the stages of hypertension severity across the lifespan in sub-Saharan Africa. The results are important for understanding progression through hypertension severity and can be used in simulating cost-effective models to evaluate policies and the burden of future healthcare.

Annual transition probabilities of overweight and obesity in older adults: Evidence from World Health Organization Study on global AGEing and adult health.

Overweight/obesity is becoming increasingly prevalent in sub-Saharan Africa including Ghana. However, transition probabilities, an essential component to develop cost-effective measures for weight management is lacking in this population. We estimated annual transition probabilities between three body mass index (BMI) categories: normal weight (BMI ≥18.5 and <25.0 kg/m2), overweight (BMI ≥25.0 and <30.0 kg/m2), and obesity (BMI ≥30.0 kg/m2), among older adults aged ≥50 years in Ghana. Data were used from a nationally representative, multistage sample of 1496 (44.3% females) older adults in both Waves 1 (2007/8) and 2 (2014/15) of the Ghana WHO SAGE. A multistage Markov model was used to estimate annual transition probabilities. We further examined the impact of specific socio-economic factors on the transition probabilities. At baseline, 22.8% were overweight and 11.1% were obese. The annual transition probability was 4.0% (95% CI: 3.4%, 4.8%) from normal weight to overweight, 11.1% (95% CI: 9.5%, 13.0%) from overweight to normal weight and 4.9% (95% CI: 3.8%, 6.2%) from overweight to obesity. For obese individuals, the probability of remaining obese, transitioning to overweight and completely reverting to normal weight was 90.2% (95% CI: 87.7%, 92.3%), 9.2% (95% CI: 7.2%, 11.6%) and 0.6% (95% CI: 0.4%, 0.8%) respectively. Being female, aged 50-65 years, urban residence, having high education and high wealth were associated with increased probability of transitioning into the overweight or obese categories. Our findings highlight the difficulty in transitioning away from obesity, especially among females. The estimated transition probabilities will be essential in health economic simulation models to determine sustainable weight management interventions.

Health service utilization and direct healthcare costs associated with obesity in older adult population in Ghana.

Obesity is a major risk factor for many chronic diseases and disabilities, with severe implications on morbidity and mortality among older adults. With an increasing prevalence of obesity among older adults in Ghana, it has become necessary to develop cost-effective strategies for its management and prevention. However, developing such strategies is challenging as body mass index (BMI)-specific utilization and costs required for cost-effectiveness analysis are not available in this population. Therefore, this study examines the associations between health services utilization as well as direct healthcare costs and overweight (BMI ≥25.00 and <30.00 kg/m2) and obesity (BMI ≥30.00 kg/m2) among older adults in Ghana. Data were used from a nationally representative, multistage sample of 3350 people aged 50+ years from the World Health Organization's Study on global AGEing and adult health (WHO-SAGE; 2014/15). Health service utilization was measured by the number of health facility visits over a 12-month period. Direct costs (2017 US dollars) included out-of-pocket payments and the National Health Insurance Scheme (NHIS) claims. Associations between utilization and BMI were examined using multivariable zero-inflated negative binomial regressions; and between costs and BMI using multivariable two-part regressions. Twenty-three percent were overweight and 13% were obese. Compared with normal-weight participants, overweight and obesity were associated with 75% and 159% more inpatient admissions, respectively. Obesity was also associated with 53% additional outpatient visits. One in five of the overweight and obese population had at least one chronic disease, and having chronic disease was associated with increased outpatient utilization. The average per person total costs for overweight was $78 and obesity was $132 compared with $35 for normal weight. The NHIS bore approximately 60% of the average total costs per person expended in 2014/15. Overweight and obese groups had significantly higher total direct healthcare costs burden of $121 million compared with $64 million for normal weight in the entire older adult Ghanaian population. Compared with normal weight, the total costs per person associated with overweight increased by 73% and more than doubled for obesity. Even though the total prevalence of overweight and obesity was about half of that of normal weight, the sum of their cost burden was almost doubled. Implementing weight reduction measures could reduce health service utilization and costs in this population.

Evaluation of the Association Between Health State Utilities and Obesity in Sub-Saharan Africa: Evidence From World Health Organization Study on Global AGEing and Adult Health Wave 2.

BACKGROUND: Obesity is a major public health challenge and its prevalence has increased across the age spectrum from 1980 to date in most parts of the world including sub-Saharan Africa. Studies that derive health state utilities (HSUs) stratified by weight status to support the conduct of economic evaluations and prioritization of cost-effective weight management interventions are lacking in sub-Saharan Africa. OBJECTIVES: To estimate age- and sex-specific HSUs for Ghana, along with HSUs by weight status. Associations between HSUs and overweight and obesity will be examined. STUDY DESIGN: Cross-sectional survey of the Ghanaian population. METHODS: Data were sourced from the World Health Organization Study of Global AGEing and Adult Health (WHO SAGE), 2014 to 2015. Using a "judgment-based mapping" method, responses to items from the World Health Organization Quality-of-Life (WHOQOL-100) used in the WHO SAGE were mapped to EQ-5D-5L profiles, and the Zimbabwe value set was applied to calculate HSUs. Poststratified sampling weights were applied to estimate mean HSUs, and a multivariable linear regression model was used to examine associations between HSUs and overweight or obesity. RESULTS: Responses from 3966 adults aged 18 to 110 years were analyzed. The mean (95% confidence interval) HSU was 0.856 (95% CI: 0.850, 0.863) for the population, 0.866 (95% CI: 0.857, 0.875) for men, and 0.849 (95% CI: 0.841, 0.856) for women. Lower mean HSUs were observed for obese individuals and with older ages. Multivariable regression analysis showed that HSUs were negatively associated with obesity (-0.024; 95% CI: -0.037, -0.011), female sex (-0.011; 95% CI: -0.020, -0.003), and older age groups in the population. CONCLUSIONS: The study provides HSUs by sex, age, and body mass index (BMI) categories for the Ghanaian population and examines associations between HSU and high BMI. Obesity was negatively associated with health state utility in the population. These data can be used in future economic evaluations for Ghana and sub-Saharan African populations.

Rapidly increasing prevalence of overweight and obesity in older Ghanaian adults from 2007-2015: Evidence from WHO-SAGE Waves 1 & 2.

BACKGROUND: Studies on changes in the prevalence and determinants of obesity in older adults living in sub-Saharan Africa are scarce. We examined recent changes in obesity prevalence and associated factors for older adults in Ghana between 2007/08 and 2014/15. METHODS: Data on adults aged 50 years and older in Ghana were drawn from the WHO SAGE 2007/08 (Wave 1; n = 4158) and 2014/15 (Wave 2; n = 1663). The weighted prevalence of obesity, overweight, normal weight and underweight, and of high central adiposity were compared in 2007/08 and 2014/15. Multinomial and binomial logistic regressions were used to examine whether the determinants of weight status based on objectively measured body mass index and waist circumference changed between the two time periods. RESULTS: The prevalence of overweight (2007/08 = 19.6%, 95% CI: 18.0-21.4%; 2014/15 = 24.5%, 95% CI: 21.7-27.5%) and obesity (2007/08 = 10.2%, 95% CI: 8.9-11.7%; 2014/15 = 15.0%, 95% CI: 12.6-17.7%) was higher in 2014/15 than 2007/08 and more than half of the population had high central adiposity (2007/08 = 57.7%, 95% CI: 55.4-60.1%; 2014/15 = 66.9%, 95% CI: 63.7-70.0%) in both study periods. While the prevalence of overweight increased in both sexes, obesity prevalence was 16% lower in males and 55% higher in females comparing 2007/08 to 2014/15. Female sex, urban residence, and high household wealth were associated with higher odds of overweight/obesity and high central adiposity. Those aged 70+ years had lower odds of obesity in both study waves. In 2014/15, females who did not meet the recommended physical activity were more likely to be obese. CONCLUSION: Over the 7-year period between the surveys, the prevalence of underweight decreased and overweight increased in both sexes, while obesity decreased in males but increased in females. The difference in obesity prevalence may point to differential impacts of past initiatives to reduce overweight and obesity, potential high-risk groups in Ghana, and the need to increase surveillance.

The role of intergenerational educational mobility and household wealth in adult obesity: Evidence from Wave 2 of the World Health Organization's Study on global AGEing and adult health.

BACKGROUND: Obesity has emerged as a major risk factor for non-communicable diseases in low and middle-income countries but may not follow typical socioeconomic status (SES)-related gradients seen in higher income countries. This study examines the associations between current and lifetime markers of SES and BMI categories (underweight, normal weight, overweight, obese) and central adiposity in Ghanaian adults. METHODS: Data from 4,464 adults (2,610 women) who participated in the World Health Organization's Study on global AGEing and adult health (SAGE) Wave 2 were examined. Multilevel multinomial and binomial logistic regression models were used to examine associations. SES markers included parental education, individual education, intergenerational educational mobility and household wealth. Intergenerational educational mobility was classified: stable-low (low parental and low individual education), stable-high (high parental and high individual education), upwardly (low parental and high individual education), or downwardly mobile (high parental and low individual education). RESULTS: The prevalence of obesity (12.9%) exceeded the prevalence of underweight (7.2%) in the population. High parental and individual education were significantly associated with higher odds of obesity and central adiposity in women. Compared to the stable low pattern, stable high (obesity: OR = 3.15; 95% CI: 1.96, 5.05; central adiposity: OR = 1.75; 95% CI: 1.03, 2.98) and upwardly (obesity: OR = 1.71; 95% CI: 11.13, 2.60; central adiposity: OR = 1.60; 95% CI: 1.08, 2.37) mobile education patterns were associated with higher odds of obesity and central adiposity in women, while stable high pattern was associated with higher odds of overweight (OR = 1.88; 95% CI: 1.11, 3.19) in men. Additionally, high compared to the lowest household wealth was associated with high odds of obesity and central adiposity in both sexes. CONCLUSION: Stable high and upwardly mobile education patterns are associated with higher odds of obesity and central adiposity in women while the stable high pattern was associated with higher odds of overweight in men.

The impact of household wealth on child survival in Ghana.

BACKGROUND: Improving child health is one of the major policy agendas for most of the governments, especially in the developing countries. These governments have been implementing various strategies such as improving healthcare financing, improving access to health, increasing educational level, and income level of the household to improve child health. Despite all these efforts, under-five and infant mortality rates remain high in many developing nations. Some previous studies examined how economic development or household's economic condition contributes to child survival in developing countries. In Ghana, the question as to what extent does economic circumstances of households reduces infant and child mortality still remain largely unanswered. Thus, the purpose of this study is to investigate the extent to which wealth affects the survival of under-five children, using data from the Demographic and Health Survey (DHS) of Ghana. METHODS: In this study, we use four waves of data from Demographic and Health Surveys (DHS) of Ghana from 1993 to 2008. The DHS is a detailed data set that provides comprehensive information on households and their demographic characteristics in Ghana. Data was obtained by distributing questionnaires to women (from 6000 households) of reproductive age between 15 and 49 years, which asked, among other things, their birth history information. The Weibull hazard model with gamma frailty was used to estimate wealth effect, as well as the trend of wealth effect on child's survival probability. RESULTS: We find that household wealth status has a significant effect on the child survival in Ghana. A child is more likely to survive when he/she is from a household with high wealth status. Among other factors, birth spacing and parental education were found to be highly significant to increase a child's survival probability. CONCLUSIONS: Our findings offer plausible mechanisms for the association of household wealth and child survival. We therefore suggest that the Government of Ghana strengthens and sustains improved livelihood programs, which reduce poverty. They should also take further initiatives that will increase adult education and improve health knowledge. To the best of our knowledge, this is the first study in Ghana that combines four cross sectional data sets from DHS to study a policy-relevant question. We extend Standard Weibull hazard model into Weibull hazard model with gamma frailty, which gives us a more accurate estimation. Finally, the findings of this study are of interest not only because they provide insights into the determinants of child health in Ghana and other developing countries, but they also suggest policies beyond the scope of health.