Burden Of Asthma Research Articles

Global burden of asthma among children and adolescents with projections to 2050: a comprehensive review and forecasted modeling study.

Understanding pediatric asthma is crucial to its effective diagnosis and intervention, as it may alleviate the adulthood disease burden. This epidemiological review describes the prevalence of asthma among individuals under 20 years of age by categorizing them into 3 age groups: 1-4, 5-9, and 10-19 years. Estimates were obtained from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021, which covered the prevalence of asthma from 1990 to 2021 across 21 GBD regions with 95% uncertainty intervals (UIs). We also projected the prevalence of pediatric asthma in 2050 by using a logistic regression predictive model from the existing literature and incorporating body mass index as a covariate with fixed coefficients over time. Overall, a continuous decline in asthma prevalence rates among children and adolescents was observed from 1990 to 2021, with higher rates in males and a peak prevalence rate in the 5-9 years group. Central Europe showed significantly increased prevalence rates compared to those of other regions. Our projection suggests that the prevalence rate of pediatric asthma will decline to approximately 2,608.05 per 100,000 population by 2050 (95% UI, 1,632.94-3,868.26), representing a 39.5% decrease from the 2021 figures. Despite these trends, asthma remains a substantial health burden for children and adolescents that may persist into adulthood. Therefore, proactive diagnosis and intervention are essential to mitigating the associated disease burden.

Respiratory risks from wildfire-specific PM2.5 across multiple countries and territories

Abstract Under a warming climate, wildfires are becoming more frequent and severe. Multicountry studies evaluating associations between wildfire fine particulate matter (PM2.5) and respiratory hospitalizations are lacking. Here we evaluate the short-term effects of wildfire-specific PM2.5 on respiratory hospitalizations from 1,052 communities across Australia, Brazil, Canada, Chile, New Zealand, Vietnam, Thailand and Taiwan, during 2000–2019. A 1 µg m−3 increase in wildfire-specific PM2.5 was associated with increased hospitalization risks for all-cause respiratory, asthma, chronic obstructive pulmonary disease, acute upper respiratory infection, influenza and pneumonia by 0.36%, 0.48%, 0.38%, 0.42%, 0.79% and 0.36%, respectively. Higher risks were observed among populations ≤19 or ≥60 years old, from low-income or high non-wildfire PM2.5 communities, and residing in Brazil, Thailand, Taiwan and Vietnam. Australia and New Zealand exhibited a greater hospitalization risk for asthma associated with wildfire-specific PM2.5. Compared with non-wildfire PM2.5, wildfire-specific PM2.5 posed greater hospitalization risks for all respiratory diseases and a greater burden of asthma. Wildfire-specific PM2.5 contributed to 42.4% of PM2.5-linked respiratory hospitalizations, dominating in Thailand. Overall, the substantial contribution of wildfire-specific PM2.5 to respiratory hospitalizations demands continued mitigation and adaptation efforts across most countries. Intervention should be prioritized for influenza, children, adolescents, the elderly and populations in low-income or high-polluted communities.

Medication-related perceptions of children and adolescents with severe asthma and moderate-to-severe atopic dermatitis: a non-interventional exploratory study.

Severe asthma and moderate-to-severe atopic dermatitis can significantly impact the lives of children and adolescents. However, real-world data on pediatric patients' perceptions of their medication are limited. This non-interventional cross-sectional study at a university hospital explored patients' perceptions. We included patients aged between 6 and 17 with severe asthma and/or moderate-to-severe atopic dermatitis. For patients treated with dupilumab, a minimum dupilumab treatment duration of 16 weeks was required. We conducted one structured interview per patient, based on a questionnaire consisting of open questions and ratings on 6-point Likert scales (response scale range: "0: not at all" to "5: very strongly"). The study included 57 participants (severe asthma: n = 31; moderate-to-severe atopic dermatitis: n = 21; both: n = 5) who reported a "rather moderate" burden of asthma (median: 2; Q25/Q75: 0.3/2.8) or atopic dermatitis (3; 1.5/3.5). They experienced their current medications as "rather helpful" (asthma: 4; 3/5; atopic dermatitis: 4; 3/5). Twelve of the participants (21%) reported refusing to take their medication because of reluctance, but all resumed treatment. All participants receiving dupilumab therapy (n = 16) reported an improvement in their disease within a maximum of 2.5 months after starting treatment. The median fear of injection decreased from 3 (0/5) before the first injection to 0.5 (0/1) at the time of the survey. In this real-world, interview-based study, we found that pediatric patients perceived treatment as highly beneficial for asthma and atopic dermatitis. Furthermore, pediatric patients seemed to respond well to dupilumab therapy in terms of both disease improvement and less fear of injection. DRKSID DRKS00028092.

Global, Regional, and National Temporal Trend and Patterns of Change in the Burden of Asthma From 1990 to 2021: An Analysis of the Global Burden of Disease Study 2021

ABSTRACTBackgroundAsthma presents a significant challenge to the global healthcare systems and imposes a heavy socioeconomic burden. Previous studies had geographical limitations and lacked comprehensive global analysis. The study utilises data from the 2021 Global Burden of Disease (GBD) study to assess the global, regional, and national burden of asthma from 1990 to 2021. It examines disease trends, highlights health inequalities and aims to provide scientific evidence for future public health strategies and the optimisation of resource allocation.MethodsData from GBD 2021 were used to estimate the incidence, prevalence, mortality, and disability‐adjusted life years (DALYs) of asthma across 21 global regions and 204 countries and territories from 1990 to 2021. Temporal trends were analysed, and the relationship between asthma burden and the socio‐demographic index (SDI) was examined using a smoothing spline model. Analyses included the slope index of inequality and the concentration index to assess health disparities, frontier analysis to estimate achievable outcomes based on development levels, and decomposition analysis to identify the drivers of changes in DALYs number.ResultsOver the past three decades, the age‐standardised burden of asthma has declined, with age‐standardised mortality and DALY rates decreasing by 46% and 44%, respectively. However, the absolute number of deaths has increased by 17%, particularly among females, especially in low and low‐middle SDI regions. Significant health inequalities persist, with high‐SDI regions benefiting from better asthma control, while low‐SDI regions face disproportionate burdens due to healthcare disparities. Frontier analysis highlights gaps between current and optimal disease burden levels, while low‐SDI regions require increased investment in asthma control. Aging, population growth, and epidemiological changes are key drivers of asthma burden trends. High body mass index (BMI) remains the leading risk factor, while smoking and occupational exposures continue to contribute significantly.ConclusionsThe global burden of asthma has declined, yet significant regional disparities persist, with low‐SDI regions experiencing higher mortality and DALYs due to limited healthcare access and environmental risks. High BMI, smoking and occupational exposures remain key contributors, requiring targeted public health interventions and lifestyle modifications.

Early-Life Ozone Exposure and Asthma and Wheeze in Children

Ozone (O3) is the most frequently exceeded air pollutant standard in the US. While short-term exposure is associated with acute respiratory health, the epidemiologic evidence linking postnatal O3 exposure to childhood asthma and wheeze is inconsistent and rarely evaluated as a mixture with other air pollutants. To determine associations between ambient O3 and subsequent asthma and wheeze outcomes both independently and in mixture with fine particulate matter and nitrogen dioxide in regions with low annual O3 concentrations. This cohort study consisted of a pooled, multisite analysis across 6 US cities using data from the prospective ECHO-PATHWAYS consortium (2007-2023). Included children had complete airway surveys, complete address histories from age 0 to 2 years, and a full term birth (≥37 weeks). Logistic regression and bayesian kernel machine regression (BKMR) mixture analyses were adjusted for child anthropomorphic, socioeconomic, and neighborhood factors. Exposure to ambient O3 in the first 2 years of life derived from a validated point-based spatiotemporal model using residential address histories. The primary outcome was asthma and wheeze at ages 4 to 6 years; the secondary outcome was asthma and wheeze at ages 8 to 9 years. Outcomes were based on caregiver reports derived from a validated survey. The analytic sample of 1188 participants had a mean (SD) age of 4.5 (0.6) years at the age 4 to 6 years visit and consisted of 614 female participants (51.7%) and 663 mothers who had a bachelor's degree or higher (55.8%). The mean (SD) O3 concentration was 26.1 (2.9) parts per billion (ppb). At age 4 to 6 years, 148 children had current asthma (12.3%) and 190 had current wheeze (15.8%). The odds ratio per 2 ppb higher O3 concentration was 1.31 (95% CI, 1.02-1.68) for current asthma and 1.30 (95% CI, 1.05-1.64) for current wheeze at age 4 to 6 years; null associations were observed for outcomes at age 8 to 9 years, and for sensitivity covariate adjustment. BKMR suggested that higher exposure to O3 in mixture was associated with current asthma and wheeze in early childhood. In this cohort study with relatively low ambient O3 exposure, early-life O3 was associated with asthma and wheeze outcomes at age 4 to 6 years and in mixture with other air pollutants but not at age 8 to 9 years. Regulating and reducing exposure to ambient O3 may help reduce the significant public health burden of asthma among US children.

The global burden and trends of asthma from 1990 to 2021, and its changes during the COVID-19 pandemic: An observational study.

The global burden and trends of asthma from 1990 to 2021, and its changes during the COVID-19 pandemic: An observational study.

Human Metapneumovirus: An Emerging Respiratory Virus

Human metapneumovirus (hMPV), a significant yet often overlooked respiratory pathogen, causes mild to severe respiratory infections, particularly in children, the elderly, and immunocompromised individuals. Discovered in 2001, hMPV is now recognized globally as a leading cause of acute respiratory infections (ARIs) and severe acute respiratory illness (SARI). It spreads through respiratory droplets and exhibits seasonal peaks, often in winter. Studies in India, such as Chennai’s 2016–2018 surveillance, detected 4% positivity in pediatric ARI cases, aligning with global rates (7–19%). However, India's dense population, high respiratory disease burden, and limited healthcare access pose unique challenges. Unlike the Northern Hemisphere’s winter peaks, India’s tropical climate may influence seasonality, while co-infections with RSV, influenza, and adenoviruses complicate diagnosis. The virus also poses risks for elderly individuals, given India’s rising burden of COPD and asthma. Despite advances in molecular diagnostics, routine hMPV testing remains limited, leading to underreporting. Diagnosis relies on real-time PCR, with multiplex RT-PCR enabling co-infection detection. While no vaccine is available, preventive measures include hand hygiene, respiratory etiquette, and isolating infected individuals. Early detection through clinical suspicion, laboratory testing, and imaging is crucial for effective management. Expanding surveillance and epidemiological studies is vital to understanding hMPV’s burden and guiding public health responses. Strengthening diagnostic capacity and awareness can help mitigate morbidity and mortality, particularly in high-risk populations in India.

Evaluating the burden of occupational asthma among individuals aged 15 and older in India: A comprehensive study on mortality and disability-adjusted life years.

Occupational asthma has become one of the most common occupational lung diseases, and its burden in India is underestimated. This study analyzed mortality and disability-adjusted life years (DALYs) caused by occupational asthma in India from 1990 to 2021 using data from the global burden of disease 2021. Data were categorized by sex, region, and age group, with age-standardized mortality rates (ASMR) and age-standardized DALYs rates (ASDR) as primary indicators to compare trends over time and across regions. According to Global Burden of Disease 2021 estimates, there were a total of 11,575.6 deaths in India attributed to occupational asthma (95% uncertainty interval, 7949.1-22,361), representing a 7.5% increase since 1990. However, ASMR and ASDR showed significant declines across all sexes compared to 1990, with reductions of 55.9% and 54.8%, respectively. Geographically, the highest burden of occupational asthma was observed in Uttar Pradesh, while Goa had the lowest. In terms of sex, the burden of mortality and disability was notably higher among males, particularly within the 15-64 age group. In 2021, the burden across all age groups was primarily driven by years of life lost. While the overall burden of mortality due to occupational asthma continues to rise in India, ASMR and ASDR have declined. However, certain regions and demographic groups, especially Uttar Pradesh and the male population, continue to bear a disproportionate share of the burden. These findings underscore the critical need for targeted prevention and control measures for occupational asthma in India.

Prevalence of Asthma, Allergic Rhinitis, and Eczema in Schoolchildren From Huambo, Angola: A Cross-Sectional Study.

Asthma is the most common chronic non-communicable disease in children with a higher prevalence in high-income countries, however, the majority of asthma-related deaths occur in low- and middle-income countries, including Angola. Therefore, we aimed to investigate the prevalence of asthma and allergic diseases among schoolchildren in Huambo, Angola's fourth most populous province. A cross-sectional study was carried out in April and May 2022 among schoolchildren aged 6-14 using the ISAAC methodology. The questionnaire included questions on asthma, allergic rhinitis, and eczema symptoms, as well as environmental exposure and risk factors. Twenty schools were randomly selected. χ 2 tests and univariate and multivariate logistic regression analyses examined associations between categorical variables. A p-value of < 0.05 was considered significant. The final sample included 1807 schoolchildren, all of whom lived in an urban area, 52.2% were girls, with a mean age of 11.9 ± 2.92 years, and 21.3% of whose parents were illiterate. Current asthma, allergic rhinitis, and eczema prevalence were 7.7%, 23.7%, and 15.8%, respectively, and none of the schoolchildren with asthma were regularly followed up by a physician or were medicated for asthma. The mother's educational level was positively associated with asthma (p = 0.022) and eczema (p = 0.042) prevalence, while having allergic rhinitis was positively associated with older schoolchildren (p < 0.001). Concerning the risk factors studied, schoolchildren with allergic rhinitis [AOR: 3.88 (95%CI 2.67-5.64); p < 0.001] and eczema [AOR: 2.99 (95%CI 2.02-4.41); p < 0.001] had a significant risk of having asthma. Our findings indicate a significant burden of asthma, allergic rhinitis, and eczema among the schoolchildren studied, underscoring the need to address this critical public health issue.

Emerging evidence for the impact of Electric Vehicle sales on childhood asthma: Can ZEV mandates help?

Emerging evidence for the impact of Electric Vehicle sales on childhood asthma: Can ZEV mandates help?

Dietary Patterns in Relation to Asthma and Wheeze Among Adolescents in a South African Rural Community

Background: The rise of asthma prevalence in recent decades has been attributed to changes in dietary patterns, especially in developing countries. Studies have also suggested that dietary patterns play an important role in both asthma development and management. This study aimed to investigate the association between consumption of various foods and environmental factors with asthma and wheeze among adolescents. Methods: A self-administered standardized International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire was used to collect data on demographics, respiratory health, exposure to air pollution, and diet on n = 2855 adolescents residing in Vhembe District, South Africa. Results: The prevalence of asthma and wheeze were 18.91% and 37.69%, respectively. Consuming various foods such as fast foods (OR = 1.41; 95% CI: 1.06–1.88), bread (OR = 0.60; 95% CI: 0.45–1.81), pasta (OR = 1.39; 95% CI: 1.06–1.84), seafood (OR = 1.79; 95% CI: 0.65–1.24), and nuts (OR = 0.85; 95% CI: 0.65–1.12) were significantly associated with asthma in the crude logistic regression analysis. Further analysis in the multiple regression model indicated a strong association of asthma with consumption of nuts (OR = 1.55; 95% CI: 1.11–2.17), seafood (OR = 1.60; 95% CI: 1.03–2.49), and cereal (OR = 0.67; 95% CI: 0.45–0.99). In relation to wheeze, consumption of meat (red) (OR = 0.77; 95% CI: 0.60–0.99) was a protective factor in the crude analysis. The multiple logistic regression model showed that, seafood (OR = 0.76; 95% CI: 0.59–0.96), fruit (OR = 0.55; 95% CI: 0.32–0.94), nuts (OR = 1.88; 95% CI: 1.50–2.66), and olive oil (OR = 1.48; 95% CI: 1.09–2.00) were significantly associated with wheeze. Conclusion: Diet plays a major role in respiratory health, especially in asthma and wheeze. Dietary changes may play a role in reducing the burden of asthma and other respiratory symptoms in adolescents.

Global, regional, and national burden of asthma and atopic dermatitis, 1990-2021, and projections to 2050: a systematic analysis of the Global Burden of Disease Study 2021.

Global, regional, and national burden of asthma and atopic dermatitis, 1990-2021, and projections to 2050: a systematic analysis of the Global Burden of Disease Study 2021.

Association of short-term exposure to PM2.5 and its components with hospital admission for asthma in Shanghai: a time-stratified case-crossover study

Introduction Associations between PM2.5 and the risk of asthma admission have been established in previous researches. However, evidence about the specific impacts of PM2.5 components on asthma-related hospitalizations across different populations and environments is limited and inconsistent. The purpose of this study was to examine the association between short-term exposure PM2.5 and its components with asthma hospital admission. Method A total of 930 people hospitalized for asthma were included in the study in Shanghai between December 2018 and December 2022. Air pollution data were assigned to individuals based on their residential address using the Tracking Air Pollution (TAP) platform. A time-stratified case-crossover design and a conditional logistic regression model were used to estimate the risk of asthma admissions related to exposure to PM2.5. We also conducted stratified analyzes by age, gender, and season. Results Each 10 μg/m³ increase in PM2.5, BC, NO3 –, NH4 +, SO4 2– and OM at lag-5 day were associated with increased risk of asthma admission, with ORs of 1.04(1.00,1.08), 2.59(0.99,6.76), 1.17(1.02,1.33), 1.33(1.06,1.66), 1.28(1.05,1.55) and 1.16(0.98,1.37), respectively. Stratified analysis showed that PM2.5 and its components had a more significant impact on the risk of asthma admission for women; individuals aged ≥ 65 years, and during cold seasons at lag-5 day. The results remained stable in the sensitivity analysis. Conclusion Short-term exposure to PM2.5 and its components (NO3 –, NH4 +, SO4 2−) increases hospitalization risk in asthma patients, particularly among women, elder and those admitted during cold seasons. It provides new insight for reducing the asthma burden associated with particulate air pollution.

Virus-induced asthma exacerbations in Vietnamese preschoolers

The health burden of asthma is mainly related to asthma exacerbation, whose most common trigger is viral infection. Additionally, preschool children experience the highest rate of morbidity from asthma. The objective of this cross-sectional study was to find out the prevalence of virus-induced asthma exacerbations among hospitalized preschoolers in the south of Vietnam with tropical weather. A total of 133 children aged 3-5 years admitted to the Children’s Hospital 1 with asthma exacerbations were enrolled. Within 24 hours of admission, nasopharyngeal swabs were tested for popular respiratory viruses by multiplex real-time polymerase chain reaction, and the genotype of human rhinovirus (HRV) was subsequently determined by Sanger sequences. Virus infections accounted for 48.9% of hospitalized preschoolers with moderate or severe asthma exacerbations. HRV was the most common pathogen (55.4%), with more than half of the cases being HRV-C (58.3%). The group of HRV-induced asthma exacerbations was older than the other group (4.3±0.9 compared to 3.7±0.7 years old, p=0.01). Also, the length of stay (LOS) was shorter in the patients with HRV-induced asthma exacerbations compared to the patients with other virus-induced exacerbations (3.2±1.5 compared to 4.4±2.7 days, p=0.04). To conclude, HRV-C was the most popular agent among hospitalized virus-induced asthma exacerbations in Vietnamese preschoolers. Compared to hospitalized asthmatic patients infected by other viruses, patients with HRV infection were older and had shorter LOS.

Global, regional, and national burden of asthma from 1990 to 2021: A systematic analysis of the global burden of disease study 2021.

Global, regional, and national burden of asthma from 1990 to 2021: A systematic analysis of the global burden of disease study 2021.

Global burden of asthma attributable to high body mass index in older adults 1990-2021 and prediction to 2050: An analysis of Global Burden of Disease Study 2021.

Previous studies have shown that high body mass index was a primary risk factor for asthma, particularly impacting older adults. This study aimed to assess the spatial and temporal trends for asthma burden attributable to high body mass index in older adults from 1990 to 2021 and to project trends up to 2050. We extracted data from the Global Burden of Disease Study 2021 for population aged over 60 years with asthma attributable to high BMI. Relevant indicators included number of deaths, disability-adjusted life years, mortality, and disability-adjusted life years rates and the rates were directly standardized. Spearman rank correlation test tested the burden against the Socio-demographic Index (SDI). Decomposition analysis was used to decompose changes in burden according to population structure, population growth, and epidemiologic changes. The Bayesian age-period-cohort model was used to predict the burden. From 1990 to 2021, despite downward trends in global mortality and disability-adjusted life-year rates, global asthma deaths, and disability-adjusted life years attributable to high body mass index increase by 69% and 46%, rising to 43,628 cases (95% CI: 18,366-71 088) and 1,223,969 years (95% CI: 526,972-1 945,426). Age-standardized mortality rates and disability-adjusted life years rates were more severe in regions with lower SDI, such as Oceania. Mortality rates and disability-adjusted life-year rates increased with age, with a higher burden observed in females compared to males. Population growth had a significant impact on the increase in deaths and disability-adjusted life years from 1990 to 2021, contributing approximately 158% and 222%, respectively. Asthma deaths and disability-adjusted life years attributable to high body mass index will continue to rise to 101,252 cases and 2,941,172 years up to 2050. The global asthma burden due to high body mass index in older adults has risen significantly and is expected to continue this trend, highlighting the importance of developing public health strategies to address this issue.

Are Treatment Adherence Factors Apparent in Patients with Asthma and to Physicians? Results from the APPaRENT3 Survey.

Patient adherence to regular controller medication is critical for improving clinical outcomes in asthma, which is consistently associated with underlying pathophysiological inflammation. This survey aimed to identify types of treatment nonadherence and associated factors, including patient characteristics that predict poor adherence, in patients with asthma. This cross-sectional online survey involved patients with asthma and physicians managing such patients from Southeast Asia (Indonesia, Malaysia, Philippines, Thailand and Vietnam) and the Middle East (Saudi Arabia and United Arab Emirates) included in the Asthma Patients' and Physicians' Perspectives on the Burden and Management of Asthma (APPaRENT)3 study. Patients and physicians shared their attitudes and beliefs regarding treatment and adherence in asthma management. Most patients (82%, 1108/1354) reported having ever received treatment with daily controller inhalers, whereas 38% used inhaled relievers at least once daily for symptomatic relief. Among those prescribed maintenance and reliever therapy, 93% were prescribed a separate inhaled reliever, with significant variation by country (P < 0.01). Erratic nonadherence (primary definition) was exhibited by 55% (462/845) of patients including those who reported at least sometimes forgetting inhaler use, with its prevalence increasing with worsening asthma severity. Nonerratic nonadherence was exhibited by 49% (415/847) of patients including those who reported using controller inhalers less than once daily. Physicians reported that 73% of patients adhered to the prescribed regular medication. Regression analysis examining both erratic (primary definition) and nonerratic nonadherence revealed that current inhaled reliever used was the only significant predictor of poor adherence (P = 0.04). Sensitivity analyses revealed that the predictors of poor adherence to controller inhaler varied depending on the definition of nonadherence employed in the study. This study revealed high rates of erratic and nonerratic nonadherence to regular controller inhalers in patients with asthma as well as discordance between adherence rates reported by patients and physicians.

Predicting future exacerbations in uncontrolled asthma: Adiscovery/validation approach using large-scale clinical proteomics.

Predicting future exacerbations in uncontrolled asthma: Adiscovery/validation approach using large-scale clinical proteomics.

The Microbiome in Asthma Heterogeneity: The Role of Multi-Omic Investigations.

Asthma is one of the most prevalent and extensively studied chronic respiratory conditions, yet the heterogeneity of asthma remains biologically puzzling. Established factors like exogenous exposures and treatment adherence contribute to variability in asthma risk and clinical outcomes. It is also clear that the endogenous factors of genetics and immune system response patterns play key roles in asthma. Despite significant existing knowledge in the above, divergent clinical trajectories and outcomes are still observed, even among individuals with similar risk profiles, biomarkers, and optimal medical management. This suggests uncaptured biological interactions that contribute to asthma's heterogeneity, for which the role of host microbiota has lately attracted much research attention. This review will highlight recent evidence in this area, focusing on bedside-to-bench investigations that have leveraged omic technologies to uncover microbiome links to asthma outcomes and immunobiology. Studies centered on the respiratory system and the use of multi-omics are noted in particular. These represent a new generation of reverse-translational investigations revealing potential functional crosstalk in host microbiomes that may drive phenotypic heterogeneity in chronic diseases like asthma. Multi-omic data offer a wide lens into ecosystem interactions within a host. This informs new hypotheses and experimental work to elucidate mechanistic pathways for unresolved asthma endotypes. Further incorporation of multi-omics into patient-centered investigations can yield new insights that hopefully lead to even more precise, microbiome-informed strategies to reduce asthma burden.

Increased asthma burden during and post the COVID-19 pandemic among U.S. adults.

Increased asthma burden during and post the COVID-19 pandemic among U.S. adults.