Emergency Department Visits for Pedestrians Injured in Motor Vehicle Traffic Crashes - United States, January 2021-December 2023.

Traffic-related pedestrian deaths in the United States reached a 40-year high in 2021. Each year, pedestrians also suffer nonfatal traffic-related injuries requiring medical treatment. Near real-time emergency department visit data from CDC's National Syndromic Surveillance Program during January 2021-December 2023 indicated that among approximately 301 million visits identified, 137,325 involved a pedestrian injury (overall visit proportion = 45.62 per 100,000 visits). The proportions of visits for pedestrian injury were 1.53-2.47 times as high among six racial and ethnic minority groups as that among non-Hispanic White persons. Compared with persons aged ≥65 years, proportions among those aged 15-24 and 25-34 years were 2.83 and 2.61 times as high, respectively. The visit proportion was 1.93 times as high among males as among females, and 1.21 times as high during September-November as during June-August. Timely pedestrian injury data can help collaborating federal, state, and local partners rapidly monitor trends, identify disparities, and implement strategies supporting the Safe System approach, a framework for preventing traffic injuries among all road users.

Asthma-Associated Emergency Department Visits During the Canadian Wildfire Smoke Episodes - United States, April- August 2023.

During April 30-August 4, 2023, smoke originating from wildfires in Canada affected most of the contiguous United States. CDC used National Syndromic Surveillance Program data to assess numbers and percentages of asthma-associated emergency department (ED) visits on days with wildfire smoke, compared with days without wildfire smoke. Wildfire smoke days were defined as days when concentrations of particulate matter (particles generally ≤2.5 µm in aerodynamic diameter) (PM2.5) triggered an Air Quality Index ≥101, corresponding to the air quality categorization, "Unhealthy for Sensitive Groups." Changes in asthma-associated ED visits were assessed across U.S. Department of Health and Human Services regions and by age. Overall, asthma-associated ED visits were 17% higher than expected during the 19 days with wildfire smoke that occurred during the study period; larger increases were observed in regions that experienced higher numbers of continuous wildfire smoke days and among persons aged 5-17 and 18-64 years. These results can help guide emergency response planning and public health communication strategies, especially in U.S. regions where wildfire smoke exposure was previously uncommon.

Increase in Acute Respiratory Illnesses Among Children and Adolescents Associated with Rhinoviruses and Enteroviruses, Including Enterovirus D68 - United States, July-September 2022.

Increases in severe respiratory illness and acute flaccid myelitis (AFM) among children and adolescents resulting from enterovirus D68 (EV-D68) infections occurred biennially in the United States during 2014, 2016, and 2018, primarily in late summer and fall. Although EV-D68 annual trends are not fully understood, EV-D68 levels were lower than expected in 2020, potentially because of implementation of COVID-19 mitigation measures (e.g., wearing face masks, enhanced hand hygiene, and physical distancing) (1). In August 2022, clinicians in several geographic areas notified CDC of an increase in hospitalizations of pediatric patients with severe respiratory illness and positive rhinovirus/enterovirus (RV/EV) test results.* Surveillance data were analyzed from multiple national data sources to characterize reported trends in acute respiratory illness (ARI), asthma/reactive airway disease (RAD) exacerbations, and the percentage of positive RV/EV and EV-D68 test results during 2022 compared with previous years. These data demonstrated an increase in emergency department (ED) visits by children and adolescents with ARI and asthma/RAD in late summer 2022. The percentage of positive RV/EV test results in national laboratory-based surveillance and the percentage of positive EV-D68 test results in pediatric sentinel surveillance also increased during this time. Previous increases in EV-D68 respiratory illness have led to substantial resource demands in some hospitals and have also coincided with increases in cases of AFM (2), a rare but serious neurologic disease affecting the spinal cord. Therefore, clinicians should consider AFM in patients with acute flaccid limb weakness, especially after respiratory illness or fever, and ensure prompt hospitalization and referral to specialty care for such cases. Clinicians should also test for poliovirus infection in patients suspected of having AFM because of the clinical similarity to acute flaccid paralysis caused by poliovirus. Ongoing surveillance for EV-D68 is critical to ensuring preparedness for possible future increases in ARI and AFM.

Trends in Acute Hepatitis of Unspecified Etiology and Adenovirus Stool Testing Results in Children - United States, 2017-2022.

In November 2021, CDC was notified of a cluster of previously healthy children with hepatitis of unknown etiology evaluated at a single U.S. hospital (1). On April 21, 2022, following an investigation of this cluster and reports of similar cases in Europe (2,3), a health advisory* was issued requesting U.S. providers to report pediatric cases† of hepatitis of unknown etiology to public health authorities. In the United States and Europe, many of these patients have also received positive adenovirus test results (1,3). Typed specimens have indicated adenovirus type 41, which typically causes gastroenteritis (1,3). Although adenovirus hepatitis has been reported in immunocompromised persons, adenovirus is not a recognized cause of hepatitis in healthy children (4). Because neither acute hepatitis of unknown etiology nor adenovirus type 41 is reportable in the United States, it is unclear whether either has recently increased above historical levels. Data from four sources were analyzed to assess trends in hepatitis-associated emergency department (ED) visits and hospitalizations, liver transplants, and adenovirus stool testing results among children in the United States. Because of potential changes in health care-seeking behavior during 2020-2021, data from October 2021-March 2022 were compared with a pre-COVID-19 pandemic baseline. These data do not suggest an increase in pediatric hepatitis or adenovirus types 40/41 above baseline levels. Pediatric hepatitis is rare, and the relatively low weekly and monthly counts of associated outcomes limit the ability to interpret small changes in incidence. Ongoing assessment of trends, in addition to enhanced epidemiologic investigations, will help contextualize reported cases of acute hepatitis of unknown etiology in U.S. children.

Using the Centers for Disease Control and Prevention's National Syndromic Surveillance Program Data to Monitor Trends in US Emergency Department Visits for Firearm Injuries, 2018 to 2019.

STUDY OBJECTIVE: We describe trends in emergency department (ED) visits for initial firearm injury encounters in the United States. METHODS: Using data from the Centers for Disease Control and Prevention's National Syndromic Surveillance Program, we analyzed monthly and yearly trends in ED visit rates involving a firearm injury (calculated as the number of firearm injury-related ED visits divided by the total number of ED visits for each month and multiplied by 100,000) by sex-specific age group and US region from 2018 to 2019 and conducted Joinpoint regression to detect trend significance. RESULTS: Among approximately 215 million ED visits captured in the National Syndromic Surveillance Program from January 2018 to December 2019, 132,767 involved a firearm injury (61.6 per 100,000 ED visits). Among males, rates of firearm injury-related ED visits significantly increased for all age groups between 15 and 64 years during the study period. Among females, rates of firearm injury-related ED visits significantly increased for all age groups between 15 and 54 years during the study period. By region, rates significantly changed in the northeast, southeast, and southwest for males and females during the study period. CONCLUSION: These analyses highlight a novel data source for monitoring trends in ED visits for firearm injuries. With increased and effective use of state and local syndromic surveillance data, in addition to improvements to firearm injury syndrome definitions by intent, public health professionals could better detect unusual patterns of firearm injuries across the United States for improved prevention and tailored response efforts.

Syndromic surveillance of vaccine-associated adverse events in U.S. emergency departments.

The Centers for Disease Control and Prevention explored use of emergency department (ED) visit data, during 2018-2020, from the National Syndromic Surveillance Program to monitor vaccine-associated adverse events (VAE) among all age groups. A combination of chief complaint terms and administrative diagnosis codes were used to detect VAE-related ED visits. Postvaccination fever was among the top 10 most frequently noted diagnoses. VAE annual trends demonstrated seasonality; visits trended upward starting in September of each year, coinciding with the administration of seasonal influenza vaccines. The 2020 VAE-related visit trend declined below the 2018 and 2019 baselines during March 22-September 5, 2020, before returning to the seasonal pattern. VAE-related visits declined in children aged 3-18 years in 2020 compared with 2018-2019, especially in the back-to-school months. These findings demonstrate that syndromic surveillance can complement traditional VAE reporting systems without an additional demand on data collection resources.

Emergency Department Visits for Suspected Suicide Attempts Among Persons Aged 12-25 Years Before and During the COVID-19 Pandemic - United States, January 2019-May 2021.

Beginning in March 2020, the COVID-19 pandemic and response, which included physical distancing and stay-at-home orders, disrupted daily life in the United States. Compared with the rate in 2019, a 31% increase in the proportion of mental health-related emergency department (ED) visits occurred among adolescents aged 12-17 years in 2020 (1). In June 2020, 25% of surveyed adults aged 18-24 years reported experiencing suicidal ideation related to the pandemic in the past 30 days (2). More recent patterns of ED visits for suspected suicide attempts among these age groups are unclear. Using data from the National Syndromic Surveillance Program (NSSP),* CDC examined trends in ED visits for suspected suicide attempts† during January 1, 2019-May 15, 2021, among persons aged 12-25 years, by sex, and at three distinct phases of the COVID-19 pandemic. Compared with the corresponding period in 2019, persons aged 12-25 years made fewer ED visits for suspected suicide attempts during March 29-April 25, 2020. However, by early May 2020, ED visit counts for suspected suicide attempts began increasing among adolescents aged 12-17 years, especially among girls. During July 26-August 22, 2020, the mean weekly number of ED visits for suspected suicide attempts among girls aged 12-17 years was 26.2% higher than during the same period a year earlier; during February 21-March 20, 2021, mean weekly ED visit counts for suspected suicide attempts were 50.6% higher among girls aged 12-17 years compared with the same period in 2019. Suicide prevention measures focused on young persons call for a comprehensive approach, that is adapted during times of infrastructure disruption, involving multisectoral partnerships (e.g., public health, mental health, schools, and families) and implementation of evidence-based strategies (3) that address the range of factors influencing suicide risk.

Emergency Department Visits for COVID-19 by Race and Ethnicity - 13 States, October-December 2020.

Hispanic or Latino (Hispanic), non-Hispanic Black or African American (Black), and non-Hispanic American Indian or Alaska Native (AI/AN) persons have experienced disproportionately higher rates of hospitalization and death attributable to COVID-19 than have non-Hispanic White (White) persons (1-4). Emergency care data offer insight into COVID-19 incidence; however, differences in use of emergency department (ED) services for COVID-19 by racial and ethnic groups are not well understood. These data, most of which are recorded within 24 hours of the visit, might be an early indicator of changing patterns in disparities. Using ED visit data from 13 states obtained from the National Syndromic Surveillance Program (NSSP), CDC assessed the number of ED visits with a COVID-19 discharge diagnosis code per 100,000 population during October-December 2020 by age and race/ethnicity. Among 5,794,050 total ED visits during this period, 282,220 (4.9%) were for COVID-19. Racial/ethnic disparities in COVID-19 ED visit rates were observed across age groups. Compared with White persons, Hispanic, AI/AN, and Black persons had significantly more COVID-19-related ED visits overall (rate ratio [RR] range = 1.39-1.77) and in all age groups through age 74 years; compared with White persons aged ≥75 years, Hispanic and AI/AN persons also had more COVID-19-related ED visits (RR = 1.91 and 1.22, respectively). These differences in ED visit rates suggest ongoing racial/ethnic disparities in COVID-19 incidence and can be used to prioritize prevention resources, including COVID-19 vaccination, to reach disproportionately affected communities and reduce the need for emergency care for COVID-19.

Emergency Department Visits for Tick Bites - United States, January 2017-December 2019.

The incidence of tickborne diseases in the United States is increasing; reported cases more than doubled from >22,000 in 2004 to >48,000 in 2016 (1). Ticks are responsible for approximately 95% of all locally acquired vectorborne diseases reported by states and the District of Columbia, with Lyme disease accounting for >80% of those cases (2). After a tick bite, persons might seek care at an emergency department (ED) for tick removal and to receive postexposure prophylaxis, which has been shown to effectively prevent Lyme disease when taken within 72 hours of a high-risk bite (3). Using data from CDC's National Syndromic Surveillance Program (NSSP), investigators examined ED tick bite visits during January 2017-December 2019 by sex, age group, U.S. region, and seasonality. During this 36-month period, 149,364 ED tick bite visits were identified. Mean cumulative incidence was 49 ED tick bite visits per 100,000 ED visits overall; incidence was highest in the Northeast (110 per 100,000 ED visits). The seasonal distribution of ED tick bite visits was bimodal: the larger peak occurred during the spring and early summer, and the smaller peak occurred in the fall. This pattern aligns with the seasonality of a known and abundant human-biter, the blacklegged tick, Ixodes scapularis (4). Compared with other age groups, pediatric patients aged 0-9 years accounted for the highest number and incidence of ED tick bite visits; incidence was higher among male patients than among females. Tick bites are not monitored by current surveillance systems because a tick bite is an event that in and of itself is not a reportable condition to health departments. Syndromic surveillance of ED tick bite visits can provide timely information that might predict temporal and geographic risk for exposure to tickborne diseases and guide actionable public health messaging such as avoiding tick habitats, wearing repellent consistently when outdoors, and performing regular tick checks during times of increased tick bite risk.

Development and Validation of a Syndrome Definition to Identify Suspected Nonfatal Heroin-Involved Overdoses Treated in Emergency Departments.

CONTEXT: The Centers for Disease Control and Prevention (CDC) works closely with states and local jurisdictions that are leveraging data from syndromic surveillance systems to identify meaningful changes in overdose trends. CDC developed a suspected nonfatal heroin overdose syndrome definition for use with emergency department (ED) data to help monitor trends at the national, state, and local levels. OBJECTIVE: This study assesses the percentage of true-positive unintentional and undetermined intent heroin-involved overdose (UUHOD) captured by this definition. DESIGN/SETTING: CDC applied the UUHOD definition to ED data available in CDC's National Syndromic Surveillance Program (NSSP). Data were analyzed from 18 states that shared access to their syndromic data in NSSP with the CDC overdose morbidity team. Data were analyzed using queries and manual reviews to identify heroin overdose diagnosis codes and text describing chief complaint reasons for ED visits. MEASURES: The percentage of true-positive UUHOD was calculated as the number of true-positives divided by the number of total visits captured by the syndrome definition. RESULTS: In total, 99 617 heroin overdose visits were identified by the syndrome definition. Among 95 323 visits identified as acute heroin-involved overdoses, based on reviews of chief complaint text and diagnosis codes, 967 (1.0%) were classified as possible intentional drug overdoses. Among all 99 617 visits, 94 356 (94.7%) were classified as true-positive UUHOD; 2226 (2.2%) and 3035 (3.0%) were classified as "no" and "maybe" UUHOD, respectively. CONCLUSION: Analysis of the CDC heroin overdose syndrome definition determined that nearly all visits were captured accurately for patients presenting to the ED for a suspected acute UUHOD. This definition will continue to be valuable for ongoing heroin overdose surveillance and epidemiologic analysis of heroin overdose patterns. CDC will evaluate possible definition refinements as new products and terms for heroin overdose emerge.

Trends in U.S. Emergency Department Visits Related to Suspected or Confirmed Child Abuse and Neglect Among Children and Adolescents Aged <18 Years Before and During the COVID-19 Pandemic - United States, January 2019-September 2020.

Heightened stress, school closures, loss of income, and social isolation resulting from the coronavirus disease 2019 (COVID-19) pandemic have increased the risk for child abuse and neglect (1). Using National Syndromic Surveillance Program (NSSP) data from January 6, 2019-September 6, 2020, CDC tabulated weekly numbers of emergency department (ED) visits related to child abuse and neglect and calculated the proportions of such visits per 100,000 ED visits, as well as the percentage of suspected or confirmed ED visits related to child abuse and neglect ending in hospitalization, overall and stratified by age group (0-4, 5-11, and 12-17 years). The total number of ED visits related to child abuse and neglect began decreasing below the corresponding 2019 period during week 11 (March 15-March 22, 2020) for all age groups examined, coinciding with the declaration of a national emergency on March 13 (2); simultaneously, the proportion of these visits per 100,000 ED visits began increasing above the 2019 baseline for all age groups. Despite decreases in the weekly number of ED visits related to child abuse and neglect, the weekly number of these visits resulting in hospitalization remained stable in 2020; however, the yearly percentage of ED visits related to child abuse and neglect resulting in hospitalization increased significantly among all age groups. Although the increased proportion of ED visits related to child abuse and neglect might be associated with a decrease in the overall number of ED visits, these findings also suggest that health care-seeking patterns have shifted during the pandemic. Hospitalizations for child abuse and neglect did not decrease in 2020, suggesting that injury severity did not decrease during the pandemic, despite decreased ED visits. Child abuse is preventable; implementation of strategies including strengthening household economic supports and creating family-friendly work policies can reduce stress during difficult times and increase children's opportunities to thrive in safe, stable, and nurturing relationships and environments (3).

Potential Indirect Effects of the COVID-19 Pandemic on Use of Emergency Departments for Acute Life-Threatening Conditions - United States, January-May 2020.

On March 13, 2020, the United States declared a national emergency in response to the coronavirus disease 2019 (COVID-19) pandemic. Subsequently, states enacted stay-at-home orders to slow the spread of SARS-CoV-2, the virus that causes COVID-19, and reduce the burden on the U.S. health care system. CDC* and the Centers for Medicare & Medicaid Services (CMS)† recommended that health care systems prioritize urgent visits and delay elective care to mitigate the spread of COVID-19 in health care settings. By May 2020, national syndromic surveillance data found that emergency department (ED) visits had declined 42% during the early months of the pandemic (1). This report describes trends in ED visits for three acute life-threatening health conditions (myocardial infarction [MI, also known as heart attack], stroke, and hyperglycemic crisis), immediately before and after declaration of the COVID-19 pandemic as a national emergency. These conditions represent acute events that always necessitate immediate emergency care, even during a public health emergency such as the COVID-19 pandemic. In the 10 weeks following the emergency declaration (March 15-May 23, 2020), ED visits declined 23% for MI, 20% for stroke, and 10% for hyperglycemic crisis, compared with the preceding 10-week period (January 5-March 14, 2020). EDs play a critical role in diagnosing and treating life-threatening conditions that might result in serious disability or death. Persons experiencing signs or symptoms of serious illness, such as severe chest pain, sudden or partial loss of motor function, altered mental state, signs of extreme hyperglycemia, or other life-threatening issues, should seek immediate emergency care, regardless of the pandemic. Clear, frequent, highly visible communication from public health and health care professionals is needed to reinforce the importance of timely care for medical emergencies and to assure the public that EDs are implementing infection prevention and control guidelines that help ensure the safety of their patients and health care personnel.

Characterizing RNA Excited States Using NMR Relaxation Dispersion.

Changes in RNA secondary structure play fundamental roles in the cellular functions of a growing number of noncoding RNAs. This chapter describes NMR-based approaches for characterizing microsecond-to-millisecond changes in RNA secondary structure that are directed toward short-lived and low-populated species often referred to as "excited states." Compared to larger scale changes in RNA secondary structure, transitions toward excited states do not require assistance from chaperones, are often orders of magnitude faster, and are localized to a small number of nearby base pairs in and around noncanonical motifs. Here, we describe a procedure for characterizing RNA excited states using off-resonance R1ρ NMR relaxation dispersion utilizing low-to-high spin-lock fields (25-3000 Hz). R1ρ NMR relaxation dispersion experiments are used to measure carbon and nitrogen chemical shifts in base and sugar moieties of the excited state. The chemical shift data are then interpreted with the aid of secondary structure prediction to infer potential excited states that feature alternative secondary structures. Candidate structures are then tested by using mutations, single-atom substitutions, or by changing physiochemical conditions, such as pH and temperature, to either stabilize or destabilize the candidate excited state. The resulting chemical shifts of the mutants or under different physiochemical conditions are then compared to those of the ground and excited states. Application is illustrated with a focus on the transactivation response element from the human immune deficiency virus type 1, which exists in dynamic equilibrium with at least two distinct excited states.

Visualizing transient Watson-Crick-like mispairs in DNA and RNA duplexes.

Rare tautomeric and anionic nucleobases are believed to have fundamental biological roles, but their prevalence and functional importance has remained elusive because they exist transiently, in low abundance, and involve subtle movements of protons that are difficult to visualize. Using NMR relaxation dispersion, we show here that wobble dG•dT and rG•rU mispairs in DNA and RNA duplexes exist in dynamic equilibrium with short-lived, low-populated Watson-Crick-like mispairs that are stabilized by rare enolic or anionic bases. These mispairs can evade Watson-Crick fidelity checkpoints and form with probabilities (10(-3) to 10(-5)) that strongly imply a universal role in replication and translation errors. Our results indicate that rare tautomeric and anionic bases are widespread in nucleic acids, expanding their structural and functional complexity beyond that attainable with canonical bases.

Evaluating the uncertainty in exchange parameters determined from off-resonance R1ρ relaxation dispersion for systems in fast exchange.

Spin relaxation in the rotating frame (R1ρ) is a powerful NMR technique for characterizing fast microsecond timescale exchange processes directed toward short-lived excited states in biomolecules. At the limit of fast exchange, only k(ex)=k(1)+k(-1) and Φex=p(G)p(E)(Δω)(2) can be determined from R1ρ data limiting the ability to characterize the structure and energetics of the excited state conformation. Here, we use simulations to examine the uncertainty with which exchange parameters can be determined for two state systems in intermediate-to-fast exchange using off-resonance R1ρ relaxation dispersion. R1ρ data computed by solving the Bloch-McConnell equations reveals small but significant asymmetry with respect to offset (R1ρ (ΔΩ)≠R1ρ (-ΔΩ)), which is a hallmark of slow-to-intermediate exchange, even under conditions of fast exchange for free precession chemical exchange line broadening (k(ex)/Δω>10). A grid search analysis combined with bootstrap and Monte-Carlo based statistical approaches for estimating uncertainty in exchange parameters reveals that both the sign and magnitude of Δω can be determined at a useful level of uncertainty for systems in fast exchange (k(ex)/Δω<10) but that this depends on the uncertainty in the R1ρ data and requires a thorough examination of the multidimensional variation of χ(2) as a function of exchange parameters. Results from simulations are complemented by analysis of experimental R1ρ data measured in three nucleic acid systems with exchange processes occurring on the slow (k(ex)/Δω=0.2; pE=∼0.7%), fast (k(ex)/Δω=∼10-16; p(E)=∼13%) and very fast (k(ex)=39,000 s(-1)) chemical shift timescales.

The value of ecologic studies: mercury concentration in ambient air and the risk of autism.

Ecologic studies of the spatial relationship between disease and sources of environmental contamination can help to ascertain the degree of risk to populations from contamination and to inform legislation to ameliorate the risk. Population risks associated with persistent low-level mercury exposure have recently begun to be of concern and current reports implicate environmental mercury as a potential contributor in the etiology of various developmental and neurodegenerative diseases including autism and Alzheimer's disease. In this demonstration of preliminary findings, we demonstrate for Bexar County Texas and Santa Clara County California, the hypothesis that the spatial structure of the occurrence of autism has a positive co-variation with the spatial structure of the distribution of mercury in ambient air. The relative risk of autism is greater in the geographic areas of higher levels of ambient mercury. We find that the higher levels of ambient mercury are geographically associated with point sources of mercury emission, such as coal-fired power plants and cement plants with coal-fired kilns. Although this does not indicate a cause, these results should not be dismissed, but rather seen as a preliminary step for generating a hypothesis for further investigation.

Narrow assessments misrepresent development and misguide policy: comment on Steinberg, Cauffman, Woolard, Graham, and Banich (2009).

Intellectual and psychosocial functioning develop along complex learning pathways. Steinberg, Cauffman, Woolard, Graham, and Banich (see record 2009-18110-001) measured these two classes of abilities with narrow, biased assessments that captured only a segment of each pathway and created misleading age patterns based on ceiling and floor effects. It is a simple matter to shift the assessments to produce the opposite pattern, with cognitive abilities appearing to develop well into adulthood and psychosocial abilities appearing to stop developing at age 16. Their measures also lacked a realistic connection to the lived behaviors of adolescents, abstracting too far from messy realities and thus lacking ecological validity and the nuanced portrait that the authors called for. A drastically different approach to assessing development is required that (a) includes the full age-related range of relevant abilities instead of a truncated set and (b) examines the variability and contextual dependence of abilities relevant to the topics of murder and abortion.

Environmental mercury release, special education rates, and autism disorder: an ecological study of Texas.

The association between environmentally released mercury, special education and autism rates in Texas was investigated using data from the Texas Education Department and the United States Environmental Protection Agency. A Poisson regression analysis adjusted for school district population size, economic and demographic factors was used. There was a significant increase in the rates of special education students and autism rates associated with increases in environmentally released mercury. On average, for each 1,000 lb of environmentally released mercury, there was a 43% increase in the rate of special education services and a 61% increase in the rate of autism. The association between environmentally released mercury and special education rates were fully mediated by increased autism rates. This ecological study suggests the need for further research regarding the association between environmentally released mercury and developmental disorders such as autism. These results have implications for policy planning and cost analysis.