Multicenter Assessment of Cryoanalgesia Use in Minimally Invasive Repair of Pectus Excavatum: A 20-center Retrospective Cohort Study.

OBJECTIVE: To assess the clinical implications of cryoanalgesia for pain management in children undergoing minimally invasive repair of pectus excavatum (MIRPE). BACKGROUND: MIRPE entails significant pain management challenges, often requiring high postoperative opioid use. Cryoanalgesia, which blocks pain signals by temporarily ablating intercostal nerves, has been recently utilized as an analgesic adjunct. We hypothesized that the use of cryoanalgesia during MIRPE would decrease postoperative opioid use and length of stay (LOS). MATERIALS AND METHODS: A multicenter retrospective cohort study of 20 US children's hospitals was conducted of children (age below 18 years) undergoing MIRPE from January 1, 2014, to August 1, 2019. Differences in total postoperative, inpatient, oral morphine equivalents per kilogram, and 30-day LOS between patients who received cryoanalgesia versus those who did not were assessed using bivariate and multivariable analysis. P value <0.05 is considered significant. RESULTS: Of 898 patients, 136 (15%) received cryoanalgesia. Groups were similar by age, sex, body mass index, comorbidities, and Haller index. Receipt of cryoanalgesia was associated with lower oral morphine equivalents per kilogram (risk ratio=0.43, 95% confidence interval: 0.33-0.57) and a shorter LOS (risk ratio=0.66, 95% confidence interval: 0.50-0.87). Complications were similar between groups (29.8% vs 22.1, P =0.07), including a similar rate of emergency department visit, readmission, and/or reoperation. CONCLUSIONS: Use of cryoanalgesia during MIRPE appears to be effective in lowering postoperative opioid requirements and LOS without increasing complication rates. With the exception of preoperative gabapentin, other adjuncts appear to increase and/or be ineffective at reducing opioid utilization. Cryoanalgesia should be considered for patients undergoing this surgery.

Extracorporeal Life Support for Respiratory Failure in Patients With Electronic Cigarette or Vaping Product Use-Associated Lung Injury.

OBJECTIVES: Electronic cigarette or vaping product use-associated lung injury is a clinical entity that can lead to respiratory failure and death. Despite the severity of electronic cigarette or vaping product use-associated lung injury, the role of extracorporeal life support in its management remains unclear. Our objective was to describe the clinical characteristics and outcomes of patients with electronic cigarette or vaping product use-associated lung injury who received extracorporeal life support. DESIGN: We performed a retrospective review of records of electronic cigarette or vaping product use-associated lung injury patients who received extracorporeal life support. Standardized data were collected via direct contact with extracorporeal life support centers. Data regarding presentation, ventilatory management, extracorporeal life support details, and outcome were analyzed. SETTING: This was a multi-institutional, international case series with patients from 10 different institutions in three different countries. PATIENTS: Patients who met criteria for confirmed electronic cigarette or vaping product use-associated lung injury (based on previously reported diagnostic criteria) and were placed on extracorporeal life support were included. Patients were identified via literature review and by direct contact with extracorporeal life support centers. MEASUREMENTS AND MAIN RESULTS: Data were collected for 14 patients ranging from 16 to 45 years old. All had confirmed vape use within 3 months of presentation. Nicotine was the most commonly used vaping product. All patients had respiratory symptoms and radiographic evidence of bilateral pulmonary opacities. IV antibiotics and corticosteroids were universally initiated. Patients were intubated for 1.9 days (range, 0-6) prior to extracorporeal life support initiation. Poor oxygenation and ventilation were the most common indications for extracorporeal life support. Five patients showed evidence of ventricular dysfunction on echocardiography. Thirteen patients (93%) were placed on venovenous extracorporeal life support, and one patient required multiple rounds of extracorporeal life support. Total extracorporeal life support duration ranged from 2 to 37 days. Thirteen patients survived to hospital discharge; one patient died of septic shock. CONCLUSIONS: Electronic cigarette or vaping product use-associated lung injury can cause refractory respiratory failure and hypoxemia. These data suggest that venovenous extracorporeal life support can be an effective treatment option for profound, refractory respiratory failure secondary to electronic cigarette or vaping product use-associated lung injury.

Cryoanalgesia is Associated With Decreased Postoperative Opioid Use in Minimally Invasive Repair of Pectus Excavatum.

BACKGROUND: Postoperative pain control is challenging after pectus excavatum repair. We aimed to understand the impact that cryoanalgesia had on opioid utilization and outcomes of pediatric patients undergoing minimally invasive repair of pectus excavatum (MIRPE). METHODS: A single-center retrospective cohort study was conducted of all patients (< 18 y) who underwent MIRPE (2011-2019). Patients receiving cryoanalgesia were compared to those who did not. The primary outcome was total postoperative, inpatient, opioid use, measured as milligrams of oral morphine equivalents per kilogram (OME/kg). Univariate and multivariable analyses were performed. RESULTS: Of 35 patients, 20 received cryoanalgesia (57%). Baseline characteristics were similar. Patients who received cryoanalgesia had a lower opioid requirement: median 2.3 mg OME/kg (IQR 1.2-3.1), versus 4.9 mg OME/kg (IQR 2.9-5.8), P < 0.001. Accounting for receipt of cryoanalgesia, epidural, and/or patient-controlled analgesia, cryoanalgesia was associated with a 3.3 mg OME/kg reduction in opioid use (P < 0.001). Median length of stay (LOS) was shorter in cryoanalgesia patients: 3.1 d (IQR 2.3-3.4), versus 5.1 d (IQR 4.3-5.4), P < 0.001. Complications within 90 d were similar between groups. CONCLUSIONS: Cryoanalgesia is an effective adjunctive pain control modality for patients undergoing MIRPE. Use of cryoanalgesia was associated with lower postoperative opioid requirements and shorter LOS, without increased short-term complications, and should be considered for enhanced recovery after MIRPE.

Pertussis and influenza immunization: perceived attitude and decision of postpartum patients.

BACKGROUND: Vaccination of pregnant patients with tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) and influenza vaccine during influenza season can reduce maternal and fetal morbidity and mortality; nevertheless, vaccination rates remain suboptimal in this patient population. To investigate the effect of a brief educational counseling session on maternal Tdap and influenza vaccination and determine factors influencing women's decision in regards to receiving Tdap and or influenza vaccine during their pregnancy. METHODS: A face-to-face semi-structured cross-sectional survey was administered to postpartum patients on their anticipated day of discharge (June 11-August 21, 2018). A brief educational counseling session about maternal pertussis and Tdap vaccine was provided to interested patients after which the Tdap vaccine was offered to eligible patients who did not receive it during their pregnancy or upon hospital admission. Medical records were reviewed to determine if surveyed patients were vaccinated prior to discharge. RESULTS: Two hundred postpartum patients were surveyed on their day of anticipated discharge. Of those who were surveyed, 103 (51.5%) had received Tdap and 80 (40.0%) had received influenza vaccinations prior to hospitalization. Among immunized patients, the common facilitators were doctor's recommendation (Tdap: 68, 54.4%; influenza: 3, 6.0%), to protect their baby (Tdap: 57, 45.6%; influenza: 17, 34.0%) and for self-protection (Tdap: 17, 13.6%; Influenza: 17, 34.0%). Of the 119 participants who had not received either Tdap or influenza vaccine prior to the survey, the barriers cited were that the vaccine was not offered by the provider (Tdap: 36, 52.2%; influenza: 29, 27.6%), belief that vaccination was unnecessary (Tdap: 5, 7.2%; influenza: 9, 8.5%), safety concerns for baby (Tdap: 4, 5.8%; influenza: 2, 1.9%). Of 97 patients who were not immunized with Tdap prior to admission but were eligible to receive vaccine, 24 (25%) were vaccinated prior to survey as part of routine hospital-based screening and vaccination program, 29 (38.2%) after our survey. CONCLUSION: Interventions to educate pregnant patients about the benefits of vaccination for their baby, addressing patient safety concerns, and vaccine administration in obstetricians' offices may significantly improve maternal vaccination rates.

Implementation of a Parent-centered Approach to the Preinduction Checklist in Pediatric Surgery.

BACKGROUND: The preinduction checklist, part of the three-phase surgical safety checklist, is performed before induction of anesthesia. Our previous research demonstrated higher checklist adherence by perioperative staff when parents were engaged in the preinduction checklist. We hypothesized that use of a parent-centered script (PCS) during the preinduction checklist would increase parent engagement and checklist adherence. METHODS: A single-center, prospective, observational study was conducted in which parents of children (<18 y) undergoing nonemergent surgeries (June 2018-July 2019) were observed before and after PCS implementation. The PCS, developed by the health care team, engaged parents by directly asking them to contribute information relevant to parent knowledge. Parent engagement was rated using a five-point Likert scale, and adherence was scored for each relevant checkpoint completed. RESULTS: Of 270 checklists, 154 (57%) occurred before and 116 (43%) after PCS implementation. Groups were similar by primary language, patient age, and type of surgery, but more postimplementation children had a prior surgery. The overall parent engagement score did not improve with the PCS (P = 0.8); however, there was an improvement in eye contact by parents. After introduction of the PCS, checklist adherence decreased from a median score of 6 (interquartile range 5-6) to 4 (interquartile range 4-5) (P < 0.001). CONCLUSIONS: Use of a PCS did not improve parent engagement during the preinduction checklist and an unexpected decline in checklist adherence was observed. Further research, with parent and staff input, is necessary to determine how best to engage parents while ensuring high checklist adherence.

Barriers to Transition to Home From the Neonatal Intensive Care Unit: A Qualitative Perspectives of Parents and Healthcare Providers.

The objective of this study was to explore the challenges faced by parents of former neonatal intensive care unit (NICU) patients in transitioning home from parents' and healthcare providers' perspective. We conducted semistructured individual and group interviews with parents of former NICU patients and healthcare providers. Themes from the individual interviews framed the group interviews' contents. The group interviews were recorded and transcribed, and thematic analysis was performed to identify themes. We conducted individual and group interviews with 16 parents and 33 inpatient and outpatient providers from November 2017 to June 2018. Individual interview participants identified several barriers experienced by parents when transitioning their infant home from the NICU including parental involvement and engagement during NICU stay and during the discharge process. Further exploration within group interviews revealed opportunities to improve discharge communication and processes, standardization of parental education that was lacking due to NICU resource constraints, support for parents' emotional state, and use of technology for infant care in the home. Parents of NICU patients face serious emotional, logistical, and knowledge challenges when transitioning their infant home from the NICU. Understanding and mitigating the challenges of transitioning infants from NICU to home require multistakeholder input from both parents and providers.

Standardized Discharge Antibiotics May Reduce Readmissions in Pediatric Perforated Appendicitis.

BACKGROUND: Based on limited evidence, the American Pediatric Surgical Association recommends 5-7 d of postoperative antibiotics in perforated appendicitis for preventing intra-abdominal abscess (IAA). In 2015, our institutional clinical practice guideline was modified to standardize prescription for 7 additional days of oral antibiotics after discharge. We hypothesized that prescribing oral antibiotics after discharge would be associated with fewer complications in perforated appendicitis. MATERIALS AND METHODS: A retrospective cohort study was conducted of pediatric (younger than 18 y) patients who underwent laparoscopic appendectomy for perforated appendicitis (August 1, 2012-April 30, 2019). Patients diagnosed with IAA before discharge or with a postoperative length of stay ≥8 d were excluded. Patient outcomes were compared prestandardization and poststandardization of discharge antibiotics. RESULTS: Of 617 patients, 212 (34.5%) were admitted prestandardization and 404 (65.5%) poststandardization. Overall, 409 patients (66.3%) received discharge antibiotics. The median total postoperative antibiotic duration was 4 d (interquartile range, 3-5) prestandardization versus 11 d (interquartile range, 10-12) poststandardization (P < 0.001). Prestandardization patients had a higher rate of IAA (8.9% versus 4.5%, P = 0.03) and were readmitted more frequently (13.1% versus 6.4%, P = 0.005). On adjusted analysis, admission poststandardization was associated with reduced odds of IAA (odds ratio, 0.51; 95% confidence interval, 0.25-1.06), but the relationship was imprecise. Admission poststandardization was significantly associated with reduced adjusted odds of readmission (odds ratio, 0.46; 95% confidence interval, 0.25-0.85). CONCLUSIONS: Prescription for seven additional days of oral antibiotics after discharge was associated with reduced odds of readmission in pediatric perforated appendicitis. This population may benefit from a longer postoperative antibiotic course than currently recommended.

Surgery and pain relief: A closer look at opioid prescription trends.

BACKGROUND: Published guidelines to reduce the use and misuse of opioids in pediatrics are limited. After the implementation of an opioid stewardship program, we aimed to investigate the prescribing patterns in pediatric surgery. METHODS: A retrospective chart review of pediatric patients who underwent general pediatric surgery procedures at a single institution between July 2021 and July 2023 was conducted. Demographics, procedure details, and opioid prescriptions at discharge were collected. The Texas Prescription Monitoring Program was cross-referenced for prescription-filled data. Descriptive statistics were performed. RESULTS: Of the 4,323 patients included, 9% (391) received an opioid prescription at the time of discharge. Among these, 82% were for burns, 7% for trauma, and 4% for pectus excavatum. Appendectomy, inguinal hernia repair, umbilical hernia repair, and circumcision did not receive any opioid prescriptions. In those who received a prescription, the median age was 4.2 years (interquartile range (IQR) 1.6, 10.4), with 58.6% being male. A total of 82.6% of patients also received prescriptions for nonopioid analgesics. The median number of prescribed doses was 13 (IQR 7, 15) for burns, 12 (IQR 9, 15) for trauma, and 12 (IQR 10, 12) for pectus excavatum. In total, 87% of prescriptions were filled. CONCLUSION: A small proportion of pediatric patients who underwent general surgery received opioid prescriptions at the time of discharge and were limited to a few conditions. Common pediatric operations received no opioid prescriptions in the 2-year study period. A total of 13% of the written prescriptions were unfilled. Future studies are needed to optimize the target pediatric patient population for opioid prescribing.

Less Dose, Same Care: Evaluating Computed Tomography Utilization for Pediatric Appendicitis.

BACKGROUND: An ultrasonography-first, magnetic resonance imaging-second protocol, and attention to dose reduction was implemented to reduce computed tomography rates for appendicitis at our institution. We aimed to compare current computed tomography usage and report radiation doses at our children's associated system hospitals and referring nonsystem hospitals. METHODS: A retrospective study of pediatric patients who underwent appendectomy and had a preoperative computed tomography scan between June 2020 and June 2023 was performed. Demographics and imaging details were abstracted from the medical record. Size-specific dose estimates and effective dose estimates were calculated for each computed tomography. Size-specific dose estimates were compared with American College of Radiology Dose Index Registry diagnostic reference levels. RESULTS: Of 1,419 patients, 409 (29%) received a computed tomography for appendicitis, a 56% reduction from previous years (2012-2015) (P < .001). Overall, 352 computed tomography scans had dose data available, of which 291 (83%) were performed at system hospitals and 61 (17%) at nonsystem hospitals. The median size-specific dose estimate per computed tomography was 11.0 mGy (interquartile range 7.0, 17.4) for nonsystem hospitals and 9.1 mGy (interquartile range 6.6, 14.0) for system hospitals. The median effective dose per computed tomography was 6.7 mSv (interquartile range 4.3, 12.9) at nonsystem hospitals and 5.1 mSv (interquartile range 3.3, 9.4) at system hospitals. Nienty-three (n = 273) computed tomography scans performed at system hospitals and 30 computed tomography scans (n = 61) at nonsystem hospitals exceeded American College of Radiology Dose Index Registry age-based diagnostic reference levels. CONCLUSION: The ultrasonography-first, magnetic resonance imaging-second protocol resulted in a significant decrease in computed tomography use for appendicitis diagnosis. Comparison of doses to American College of Radiology Dose Index Registry reference levels suggests that computed tomography protocol optimization may allow for dose reduction at some facilities.

Impact of Cryoanalgesia Use During Minimally Invasive Pectus Excavatum Repair on Hospital Days and Total Hospital Costs Among Pediatric Patients.

INTRODUCTION: Surgical repair of pectus excavatum is a painful procedure requiring multimodal pain control with historically prolonged hospital stay. This study aimed to evaluate the impact of cryoanalgesia during minimally invasive repair of pectus excavatum (MIRPE) on hospital days (HDs), total hospital costs (HCs), and complications. We hypothesized that cryoanalgesia would be associated with reduced HDs and total HCs with no increase in post-operative complications. METHODS: We conducted a retrospective review of pediatric patients who underwent MIRPE from 2011 to 2021. MIRPE details and post-operative outcomes within 90 days were abstracted. Total HDs included the index MIRPE admission and readmissions within 90 days. HCs were obtained from the hospital accounting system, retroactively adjusting for medical inflation. Bayesian generalized linear models with neutral prior assuming no effect were used. Differences between treatment groups were assessed using gamma distribution (HDs and HCs) and poisson (post-operative complications). All models used log link and controlled for age, gender, race, and Haller index. RESULTS: Forty-four patients underwent MIRPE during the study period. Cryoanalgesia was utilized in 29 (66%) patients. The probability of a reduction with cryoanalgesia vs. no cryoanalgesia was 99% for HDs (3.0 vs. 5.4 days; Bayesian RR: 0.6, 95% CrI: 0.5-0.8), 89% for HCs ($18,787 vs. $19,667; RR: 0.9, 95% CrI: 0.8-1.1), and 70% for postoperative complications (17% vs 33%; RR: 0.8, 95% CrI: 0.3-1.9). CONCLUSION: Cryoanalgesia use in MIRPE likely reduced HDs, HCs, and post-operative complications. Further research is warranted to confirm these findings in large prospective studies. LEVEL OF EVIDENCE: Level III.

Birth weight predicts patient outcomes in infants who undergo congenital diaphragmatic hernia repair.

PURPOSE: The purpose of this study was to analyze the clinical characteristics and outcomes of low birthweight (LBW) infants with congenital diaphragmatic hernia (CDH) compared to normal birthweight (NBW) infants with CDH. We hypothesized that LBW was associated with increased mortality, decreased extracorporeal life support (ECLS) utilization, and increased pulmonary morbidity in CDH patients. METHODS: Patients in the CDH Study Group from 2007 to 2018 were included. LBW was defined as <2.5 kg. Clinical characteristics and outcomes for LBW patients were compared to normal birthweight (NBW) patients using univariate and multivariable analyses. RESULTS: Of 5,586 patients, 1,157 (21%) were LBW. LBW infants had more congenital anomalies and larger diaphragmatic defects than NBW infants. ECLS utilization was decreased, and overall mortality was increased among LBW infants compared to NBW infants. A 1 kg increase in birthweight was associated with 34% higher odds of survival after repair (adjusted Odds Ratio 1.34, 95% CI 1.03-1.76; p = .03). LBW infants had longer durations of mechanical ventilation and were more likely to require supplemental oxygen at 30 days and at the time of discharge. CONCLUSION: LBW is a risk factor for mortality and pulmonary morbidity in CDH. Prolonged oxygen requirement and increased length of stay are important considerations when managing this population.

Variability in opioid prescribing practices, knowledge, and beliefs: A survey of providers caring for pediatric surgical patients.

BACKGROUND/PURPOSE: Comprehensive opioid stewardship programs require collective stakeholder alignment and proficiency. We aimed to determine opioid-related prescribing practices, knowledge, and beliefs among providers who care for pediatric surgical patients. METHODS: A single-center, cross-sectional survey was conducted of attending physicians, residents, and advanced practice providers (APPs), who managed pediatric surgical patients. RESULTS: Of 110 providers surveyed, 75% completed the survey. Over half of respondents (n = 43, 52%) reported always/very often prescribing opioids at discharge, with residents reporting the highest rate (66%). Provider types had varying prescribing patterns, including what types of opioids and non-opioids they prescribed. There was a lack of formal training, particularly among residents, of which only 42% reported receiving formal opioid prescribing education. Finally, although only 28% of providers felt that the opioid epidemic affects children, 48% believed pediatric providers' prescribing patterns contributed to the opioid epidemic as a whole, and 80% reported changing their prescribing practices in response. CONCLUSIONS: Significant variability exists in opioid prescribing practices, knowledge, and beliefs among providers who care for pediatric surgical patients. Effective opioid stewardship requires comprehensive policies, pediatric specific guidelines, and education for all providers caring for children to align provider proficiency and optimize prescribing patterns.

Telemedicine as a component of forward triage in a pandemic.

OBJECTIVE(S): Coronavirus disease 2019 (COVID-19) presents an enormous challenge to healthcare systems globally. Optimizing access to healthcare while minimizing face-to-face patient encounters is critical to limiting exposures, conserving resources, and preserving health. We aimed to evaluate the utility of a COVID-focused telehealth program in avoiding potential in-person visits while maintaining high patient satisfaction. METHODS: All patients with COVID-related virtual visits at our center between March and May 2020 were included. Demographic, satisfaction, and clinical information were gathered using a modified, validated telehealth satisfaction questionnaire disseminated via email or telephone. Data were analyzed using Stata. RESULTS: Of 581 eligible patients, 180 (31%) responded to the survey. Symptoms (73%) and possible exposure (22%) were the main reasons cited for pursuing a virtual visit; cough (44%) and fever (36%) were the most common presenting symptoms. Regarding patient satisfaction, most patients rated the experience as "very good" or "excellent", and 94% of respondents said they would recommend COVID-focused triage through telehealth to others. Over 81% of patients indicated that, if telehealth was not an option, they would have sought an in-person encounter. Ultimately, only 27% of patients reported pursuing a face-to-face encounter after participating in the virtual visit. CONCLUSION: Based on patient self-reporting, telemedicine potentially prevented face-to-face COVID-related encounters. Patients expressed satisfaction with the virtual process and were less likely to pursue in-person consultation. Leveraging a telehealth strategy for forward triage has the potential to reduce exposures while conserving healthcare resources.

Prophylactic intraabdominal drains do not confer benefit in pediatric perforated appendicitis: Results from a quality improvement initiative.

BACKGROUND/PURPOSE: Prophylactic, intraabdominal drains have been used to prevent intraabdominal abscess (IAA) after perforated appendicitis. We hypothesized that routine drain placement would reduce the IAA rate in pediatric perforated appendicitis. METHODS: A 27-month quality improvement (QI) initiative was conducted: closed-suction, intraabdominal drains were placed intraoperatively in pediatric (age < 18) perforated appendicitis patients. QI patients were compared to controls admitted during the preceding 8 months and following 4 months. The primary outcome was 30-day IAA rate. Univariate and multivariate analyses were performed. RESULTS: Two hundred seventy QI patients were compared to 109 controls. There was 100% compliance during 21 of 27 months of the QI initiative; only 7 QI patients did not receive drains. IAA occurred in 20.0% of QI patients and 22.9% of control (p = 0.52). After adjustment, the QI initiative was not associated with reduced odds of IAA (OR 0.83, 95% CI 0.48-1.44). Median length of stay was longer in QI patients during the index admission (p = 0.03) and over 30 postoperative days (p = 0.03), but these relationships did not persist after adjustment. CONCLUSIONS: A QI initiative investigating prophylactic, intraabdominal drain placement in perforated appendicitis did not reduce the IAA rate. We recommend against routine drain placement in pediatric perforated appendicitis. LEVEL OF EVIDENCE: Level III.

Risk factors for nonaccidental burns in children.

BACKGROUND: The relative influences of baseline risk factors for pediatric nonaccidental burns have not been well described. We evaluated baseline characteristics of pediatric nonaccidental burn patients and their primary caretakers. METHODS: A single-center retrospective cohort study was conducted of pediatric (age < 17) burn patients from July 1, 2013, to June 30, 2018. The primary outcome was nonaccidental burn, defined as burn secondary to abuse or neglect as determined by the inpatient child protection team or Child Protective Services. Univariate and multivariate analyses were performed. RESULTS: Of 489 burn patients, 47 (9.6%) suffered nonaccidental burns. Nonaccidental burn patients more frequently had a history of Child Protective Services involvement (48.9% vs 9.7%, P < .001), as did their primary caretakers (59.6% vs 10.9%, P < .001). Non-Hispanic black children had higher rates of Child Protective Services referral (50.7% vs 26.7%, P < .001) and nonaccidental burn diagnosis (18.9% vs 5.6%, P < .001) than children of other races/ethnicities. On multivariate analysis, caretaker involvement with CPS (odds ratio 7.53, 95% confidence interval 3.38-16.77) and non-Hispanic black race/ethnicity (odds ratio 3.28, 95% confidence interval 1.29-8.36) were associated with nonaccidental burn. CONCLUSION: Caretaker history of Child Protective Services involvement and non-Hispanic black race/ethnicity were associated with increased odds of pediatric nonaccidental burn. Prospective research is necessary to determine whether these represent true risk factors for nonaccidental burn or are the result of other confounders, such as socioeconomic status.