Effects of Inclusion of Food Purchase Restrictions and Incentives in a Food Benefit Program on Diet Quality and Food Purchasing: Results From a Randomized Trial.

BACKGROUND: There is interest in reshaping the Supplemental Nutrition Assistance Program (SNAP) to better support family nutrition. OBJECTIVE: The Grocery Assistance Program Study (GAPS) for Families evaluated the effects of prohibiting using program funds for the purchase of certain sugary foods on the nutritional quality of foods purchased and consumed by program participants. DESIGN: A randomized experimental trial was carried out with participants randomized to one of three food benefit conditions. Baseline and follow-up measures collected included interviewer-administered 24-hour dietary recalls, food purchase receipts, food security, height, and weight. PARTICIPANT/SETTING: Adult-child dyads in households eligible for SNAP but currently not enrolled were recruited from the Minneapolis/St Paul MN metropolitan area from May of 2018 through May of 2019. A total of 293 adult-child dyads received the intervention as allocated. Of these dyads, 233 adults completed follow-up measures and met criteria for inclusion in the analytic sample, resulting in an attrition rate of 20.5%. A total of 224 children completed follow-up measures and met criteria for inclusion in the analytic sample, resulting in an attrition rate of 23.5%. INTERVENTION: Participants were randomized to 1 of 3 conditions: restriction (not allowed to buy sugar-sweetened beverages [SSB], sweet baked goods, or candy with program funds); restriction paired with incentive (30% incentive for fruits and vegetables [FV] purchased with funds); and control (funds provided with no restrictions or incentives). Funds were provided on a 4-week cycle for 20 weeks via a study-provided debit card. MAIN OUTCOME MEASURES: The primary outcome was the Healthy Eating Index (HEI)-2015 total score. Additional outcomes included selected HEI-2015 component scores; energy intake; food security; body weight; and purchasing of SSB, sweet baked goods, candies, fruits, and vegetables. STATISTICAL ANALYSIS: Linear regression analyses were conducted with change in the outcome regressed on treatment condition for the primary outcome analyses. RESULTS: No differences were observed between conditions in change in the nutrition and food security measures examined. Purchases of SSB and sweet baked goods and candies significantly differed by experimental condition. Purchase of restricted foods was lower at follow-up in the restriction and restriction paired with incentive conditions compared with the control condition. For example, spending on SSB at follow-up was significantly lower in the restriction ($2.66/week) and restriction paired with incentive ($2.06/week) conditions in comparison with control condition ($4.44/week) (P < 0.0003 and P < 0.0001, respectively). CONCLUSIONS: This study failed to find evidence in support of prohibiting the purchase of sugary foods with food program funds as a strategy to improve program participant nutrition, even when paired with an FV incentive. Research carried out in the context of the SNAP program is needed for a more robust evidence base.

Examining perceived risk to bovine tuberculosis through factorial survey to inform policymaking for zoonotic diseases control and surveillance.

Prevention and control of infectious diseases in livestock is dependent upon perceived risk and susceptibility, including the prevention of between-herd transmission of bovine tuberculosis through introductions of cattle to susceptible herds. To examine how perceived risk and susceptibility can help to inform policymaking in disease surveillance and control, we used factorial surveys to profile risk perceptions of cattle producers. We found that government indemnity and slaughtering policy did not impact the cattle purchasing behavior of producers who responded to our survey, but rather through other attributes such as the reliability or reputation of the seller. In addition, we identified significant production type and gender differences in purchasing behavior and risk perception. Finally, clustering analysis revealed a group of high-risk respondents characterized as experienced and very dedicated owners of established medium to large size herds. With the increasing availability of business data, assessment of producer's behavior, personalities and attitudes allows policymakers to understand the needs of cattle producers and develop tailored programs that will improve producer cooperation with government agencies.

Evaluation of the type I error rate when using parametric bootstrap analysis of a cluster randomized controlled trial with binary outcomes and a small number of clusters.

BACKGROUND: Cluster randomized controlled trials (cRCTs) are increasingly used but must be analyzed carefully. We conducted a simulation study to evaluate the validity of a parametric bootstrap (PB) approach with respect to the empirical type I error rate for a cRCT with binary outcomes and a small number of clusters. METHODS: We simulated a case study with a binary (0/1) outcome, four clusters, and 100 subjects per cluster. To compare the validity of the test with respect to error rate, we simulated the same experiment with K=10, 20, and 30 clusters, each with 2,000 simulated datasets. To test the null hypothesis, we used a generalized linear mixed model including a random intercept for clusters and obtained p-values based on likelihood ratio tests (LRTs) using the parametric bootstrap method as implemented in the R package "pbkrtest". RESULTS: The PB test produced error rates of 9.1%, 5.5%, 4.9%, and 5.0% on average across all ICC values for K=4, K=10, K=20, and K=30, respectively. The error rates were higher, ranging from 9.1% to 36.5% for K=4, in the models with singular fits (i.e., ignoring clustering) because the ICC was estimated to be zero. CONCLUSION: Using the parametric bootstrap for cRCTs with a small number of clusters results in inflated error rates and is not valid.

Perceptions of a food benefit programme that includes financial incentives for the purchase of fruits and vegetables and restrictions on the purchase of foods high in added sugar.

OBJECTIVE: To report perspectives of participants in a food benefit programme that includes foods high in added sugar (FAS) restrictions and FAS restrictions paired with fruits and vegetables (F/V) incentives. DESIGN: Randomised experimental trial in which participant perspectives were an exploratory study outcome. SETTING: Participants were randomised into one of three Supplemental Nutrition Assistance Program (SNAP)-like food benefit programme groups: (1) restriction: not allowed to buy FAS with benefits; (2) restriction paired with incentive: not allowed to buy FAS with benefits and 30 % financial incentive on eligible F/V purchased using benefits; or (3) control: same food purchasing rules as SNAP. Participants were asked questions to assess programme satisfaction. PARTICIPANTS: Adults in the Minneapolis-St. Paul, MN metropolitan area, eligible for but not currently participating in SNAP who completed baseline and follow-up study measures (n 254). RESULTS: Among remaining households in each group, most found the programme helpful in buying nutritious foods (88·2 %-95·7 %) and were satisfied with the programme (89·1 %-93·0 %). Sensitivity analysis results indicate that reported helpfulness and satisfaction with the programme may in some instances be lower among the restriction and the restrictions paired with incentive groups in comparison to the control group. CONCLUSIONS: A food benefit programme that includes restriction on purchase of FAS or restriction paired with a financial incentive for F/V purchases may be acceptable to most SNAP-eligible households with children.

Advancing the Social Epidemiology Mission of the American Journal of Epidemiology.

Social epidemiology is concerned with how social forces influence population health. Rather than focusing on a single disease (as in cancer or cardiovascular epidemiology) or a single type of exposure (e.g., nutritional epidemiology), social epidemiology encompasses all the social and economic determinants of health, both historical and contemporary. These include features of social and physical environments, the network of relationships in a society, and the institutions, politics, policies, norms and cultures that shape all of these forces. This commentary presents the perspective of several editors at the Journal with expertise in social epidemiology. We articulate our thinking to encourage submissions to the Journal that: 1) expand knowledge of emerging and underresearched social determinants of population health; 2) advance new empirical evidence on the determinants of health inequities and solutions to advance health equity; 3) generate evidence to inform the translation of research on social determinants of health into public health impact; 4) contribute to innovation in methods to improve the rigor and relevance of social epidemiology; and 5) encourage critical self-reflection on the direction, challenges, successes, and failures of the field.

Randomization, design and analysis for interdependency in aging research: no person or mouse is an island.

Investigators traditionally use randomized designs and corresponding analysis procedures to make causal inferences about the effects of interventions, assuming independence between an individual's outcome and treatment assignment and the outcomes of other individuals in the study. Often, such independence may not hold. We provide examples of interdependency in model organism studies and human trials and group effects in aging research and then discuss methodologic issues and solutions. We group methodologic issues as they pertain to (1) single-stage individually randomized trials; (2) cluster-randomized controlled trials; (3) pseudo-cluster-randomized trials; (4) individually randomized group treatment; and (5) two-stage randomized designs. Although we present possible strategies for design and analysis to improve the rigor, accuracy and reproducibility of the science, we also acknowledge real-world constraints. Consequences of nonadherence, differential attrition or missing data, unintended exposure to multiple treatments and other practical realities can be reduced with careful planning, proper study designs and best practices.

The interaction of adverse childhood experiences and gender as risk factors for depression and anxiety disorders in US adults: a cross-sectional study.

BACKGROUND: Exposure to adverse childhood experiences (ACEs) and being female are distinct risk factors for having a major depressive episode (MDE) or an anxiety disorder (AD) in adulthood, but it is unclear whether these two risk factors are synergistic. The purpose of this study was to determine whether exposure to ACEs and being female are more than additive (synergistic) in their association with MDE and AD in US adults. METHODS: We pooled cross-sectional survey data in the Midlife in the United States study from two nationally-representative cohorts of English-speaking US adults. Data from the first cohort were collected in 2004-2006 and from the second in 2011-2014. Data from both cohorts included the 12-month prevalence of MDE and AD (generalized anxiety disorder or panic disorder) assessed with the Composite International Diagnostic Interview Short Form, gender (here termed female and male), and the count of five categories of exposure to ACEs: physical, sexual, or emotional abuse; household alcohol or substance abuse; and parental separation or divorce. RESULTS: Of the 5834 survey respondents, 4344 (74.5%) with complete data on ACEs were included in the analysis. Mean (SD) age was 54.1 (13.8) years and 53.9% were female. The prevalences of MDE, AD, and exposure to 3-5 categories of ACEs were 13.7, 10.0, and 12.5%, respectively. After adjusting for covariates (age, race, and current and childhood socioeconomic disadvantage), for those with both risk factors (female and 3-5 ACEs) the prevalence of MDE was 26.9%. This was 10.2% (95% CI: 1.8, 18.5%) higher than the expected prevalence based on the additive associations of the two risk factors. The adjusted prevalence of AD among females with 3-5 ACEs was 21.9%, which was 11.4% (95% CI: 4.0, 18.9%) higher than the expected prevalence. CONCLUSIONS: For both MDE and AD, there was synergy between the two risk factors of exposure to ACEs and being female. Identification and treatment of MDE and AD may benefit from understanding the mechanisms involved in the synergistic interaction of gender with ACEs.

Errors in the implementation, analysis, and reporting of randomization within obesity and nutrition research: a guide to their avoidance.

Randomization is an important tool used to establish causal inferences in studies designed to further our understanding of questions related to obesity and nutrition. To take advantage of the inferences afforded by randomization, scientific standards must be upheld during the planning, execution, analysis, and reporting of such studies. We discuss ten errors in randomized experiments from real-world examples from the literature and outline best practices for their avoidance. These ten errors include: representing nonrandom allocation as random, failing to adequately conceal allocation, not accounting for changing allocation ratios, replacing subjects in nonrandom ways, failing to account for non-independence, drawing inferences by comparing statistical significance from within-group comparisons instead of between-groups, pooling data and breaking the randomized design, failing to account for missing data, failing to report sufficient information to understand study methods, and failing to frame the causal question as testing the randomized assignment per se. We hope that these examples will aid researchers, reviewers, journal editors, and other readers to endeavor to a high standard of scientific rigor in randomized experiments within obesity and nutrition research.

Neighborhood Socioeconomic Status and Identification of Patients With CKD Using Electronic Health Records.

RATIONALE & OBJECTIVE: Screening for chronic kidney disease (CKD) is recommended for patients with diabetes and hypertension as stated by the respective professional societies. However, CKD, a silent disease usually detected at later stages, is associated with low socioeconomic status (SES). We assessed whether adding census tract SES status to the standard screening approach improves our ability to identify patients with CKD. STUDY DESIGN: Screening test analysis. SETTINGS & PARTICIPANTS: Electronic health records (EHR) of 256,162 patients seen at a health care system in the 7-county Minneapolis/St. Paul area and linked census tract data. EXPOSURE: The first quartile of census tract SES (median value of owner-occupied housing units <$165,200; average household income <$35,935; percentage of residents >25 years of age with a bachelor's degree or higher <20.4%), hypertension, and diabetes. OUTCOMES: CKD (eGFR <60 mL/min/1.73 m2, or urinary albumin-creatinine ratio >30mg/g, or urinary protein-creatinine ratio >150mg/g, or urinary analysis [albuminuria] >30 mg/d). ANALYTICAL APPROACH: Sensitivity, specificity, and number needed to screen (NNS) to detect CKD if we screened patients who had hypertension and/or diabetes and/or who lived in low-SES tracts (belonging to the first quartile of any of the 3 measures of tract SES) versus the standard approach. RESULTS: CKD was prevalent in 13% of our cohort. Sensitivity, specificity, and NNS of detecting CKD after adding tract SES to the screening approach were 67% (95% CI, 66.2%-67.2%), 61% (95% CI, 61.1%-61.5%), and 5, respectively. With the standard approach, sensitivity of detecting CKD was 60% (95% CI, 59.4%-60.4%), specificity was 73% (95% CI, 72.4%-72.7%), and NNS was 4. LIMITATIONS: One health care system and selection bias. CONCLUSIONS: Leveraging patients' addresses from the EHR and adding tract-level SES to the standard screening approach modestly increases the sensitivity of detecting patients with CKD at a cost of decreased specificity. Identifying further factors that improve CKD detection at an early stage are needed to slow the progression of CKD and prevent cardiovascular complications.

Within- and Between-Household Variation in Food Expenditures Among Low-Income Households Using a Novel Simple Annotated Receipt Method.

Background: Household food purchasing behavior has gained interest as an intervention to improve nutrition and nutrition-associated outcomes. However, evaluating food expenditures is challenging in epidemiological studies. Assessment methods that are both valid and feasible for use among diverse, low-income populations are needed. We therefore developed a novel simple annotated receipt method to assess household food purchasing. First, we describe and evaluate the extent to which the method captures food purchasing information. We then evaluate within- and between-household variation in weekly food purchasing to determine sample sizes and the number of weeks of data needed to measure household food purchasing with adequate precision. Methods: Four weeks of food purchase receipt data were collected from 260 low-income households in the Minneapolis-St. Paul metropolitan area. The proportion of receipt line items that could not be coded into one of 11 food categories (unidentified) was calculated, and a zero-inflated negative binomial regression was used to evaluate the association between unidentified receipt items and participant characteristics and store type. Within- and between-household coefficients of variation were calculated for total food expenditures and several food categories. Results: A low proportion of receipt line items (1.6%) could not be coded into a food category and the incidence of unidentified items did not appreciably vary by participant characteristics. Weekly expenditures on foods high in added sugar had higher within- and between-household coefficients of variation than weekly fruit and vegetable expenditures. To estimate mean weekly food expenditures within 20% of the group's usual ("true") expenditures, 72 households were required. Nine weeks of data were required to achieve an r = 0.90 between observed and usual weekly food expenditures. Conclusions: The simple annotated receipt method may be a feasible tool for use in assessing food expenditures of low-income, diverse populations. Within- and between-household coefficients of variation suggest that the number of weeks of data or group sizes required to precisely estimate usual household expenditures is higher for foods high in added sugar compared to fruits and vegetables.

Efficacy of the 'Stand and Move at Work' multicomponent workplace intervention to reduce sedentary time and improve cardiometabolic risk: a group randomized clinical trial.

BACKGROUND: Sedentary time is associated with chronic disease and premature mortality. We tested a multilevel workplace intervention with and without sit-stand workstations to reduce sedentary time and lower cardiometabolic risk. METHODS: Stand and Move at Work was a group (cluster) randomized trial conducted between January 2016 and December 2017 among full-time employees; ≥18 years; and in academic, industry/healthcare, and government worksites in Phoenix, Arizona and Minneapolis/St. Paul, Minnesota, USA. Eligible worksites were randomized to (a) MOVE+, a multilevel intervention targeting reduction in sedentary time and increases in light physical activity (LPA); or (b) STAND+, the MOVE+ intervention along with sit-stand workstations to allow employees to sit or stand while working. The primary endpoints were objectively-measured workplace sitting and LPA at 12 months. The secondary endpoint was a clustered cardiometabolic risk score (blood pressure, glucose, insulin, triglycerides, and HDL-cholesterol) at 12 months. RESULTS: Worksites (N = 24; academic [n = 8], industry/healthcare [n = 8], and government [n = 8] sectors) and employees (N = 630; 27 ± 8 per worksite; 45 ± 11 years of age, 74% female) were enrolled. All worksites were retained and 487 participants completed the intervention and provided data for the primary endpoint. The adjusted between arm difference in sitting at 12 months was - 59.2 (CI: - 74.6,-43.8) min per 8 h workday, favoring STAND+, and in LPA at 12 months was + 2.2 (- 0.9,5.4) min per 8 h workday. Change in the clustered metabolic risk score was small and not statistically significant, but favored STAND+. In an exploratory subgroup of 95 participants with prediabetes or diabetes, the effect sizes were larger and clinically meaningful, all favoring STAND+, including blood glucose, triglycerides, systolic blood pressure, glycated hemoglobin, LDL-cholesterol, body weight, and body fat. CONCLUSIONS: Multilevel workplace interventions that include the use of sit-stand workstations are effective for large reductions in sitting time over 12 months. Among those with prediabetes or diabetes, clinical improvements in cardiometabolic risk factors and body weight may be realized. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02566317 . Registered 2 October 2015, first participant enrolled 11 January 2016.

A randomized, placebo-controlled crossover trial of a decaffeinated energy drink shows no significant acute effect on mental energy.

BACKGROUND: "Energy drinks" are heavily marketed to the general public, across the age spectrum. The efficacy of decaffeinated energy drinks in enhancing subjective feelings of energy (s-energy) is controversial. OBJECTIVE: The authors sought to test the efficacy of the caffeine-free version of a popular energy drink compared with a placebo drink. METHODS: This study was a randomized, double-blind, placebo-controlled, crossover trial in 223 healthy men and women aged 18-70 y with intention-to-treat and completers analysis. Participants were randomly assigned to consumption of either the decaffeinated energy drink or a placebo drink on testing day 1, and the other drink a week later. A battery of computer-based mood and cognitive tests to assess s-energy was conducted at baseline and at 0.5, 2.5, and 5 h post-ingestion. The main outcome measures were 1) mood, which was assessed by using a General Status Check Scale and the Profile of Mood States 2nd edition brief form, and 2) cognitive measures, including the N-back task (reaction time and accuracy), Reaction Time test, Flanker task (distraction avoidance), and Rapid Visual Information Processing test. RESULTS: No statistically significant or meaningful benefits were observed for any outcome measure, including mood and cognitive measures. Analyses of mean differences, slopes, and median differences were consistent. CONCLUSIONS: No differences were detected across a range of mood/cognitive/behavioral/s-energy-level tests after consumption of the energy drink compared with a placebo drink in this diverse sample of adults. Thus, we found strong evidence that the energy drink is not efficacious in enhancing s-energy levels, nor any related cognitive or behavioral variables measured. In light of federal regulations, these findings suggest that labeling and marketing of some products which claim to provide these benefits may be unsubstantiated. This trial was registered at www.clinicaltrials.gov as NCT02727920.

Impact of the Change Starts at Home Trial on Women's experience of intimate partner violence in Nepal.

Intimate partner violence (IPV) affects 1 in 3 women worldwide. Research in low- and middle-income countries suggests that multicomponent interventions incorporating media, group work, and community mobilization may be effective at changing social norms that enable such violence. Our study aimed to evaluate the impact of a radio programme plus community engagement versus radio programming alone on the 12-month prevalence of IPV. Using a cluster randomized, repeat cross-sectional, single-blinded approach, thirty-six village communities were pair-matched within three districts in Nepal and randomly assigned to either control or intervention. Both groups were exposed to social behaviour change communication through radio programming. In addition, weekly listening and discussion groups (LDGs) were formed in intervention communities to meet and discuss radio programming over the 40-week intervention period. Participants were also exposed to other community mobilization activities such as street theatre and messaging from local leaders who were engaged in intervention programming. IPV was measured at baseline, 12 months post-baseline at program conclusion, and 28 months post-baseline using a simple random sample of 40 married women per cluster (n = approximately 1440 at each time point) along with 382 women who participated in the LDGs. Although control and intervention groups were demographically similar, baseline rates of IPV were higher in control areas. The trend in IPV for both groups was nonlinear, largely declining at midline (control condition) and rising again at endline (control and intervention conditions), possibly reflecting greater reporting due to awareness-raising activities. Significant differences between the two groups were largely absent at endline. Higher LDG attendance was associated with decreases in several forms of IPV, some of which persisted to endline. These findings suggest that intensive community engagement over longer timespans or social network measurement may be necessary to detect significant changes at the community level (NCT02942433).

Examining Potential Psychosocial Mediators in a Physical Activity Intervention for Older Adults.

The purpose of this study was to examine psychosocial constructs targeted as potential mediators in a prior physical activity (PA) intervention study. This secondary analysis used data from 102 older adults randomized to one of four conditions-within a 2 (Interpersonal Strategies: yes, no) x 2 (Intrapersonal Strategies: yes, no) factorial design. We tested intervention effects on social support, self-efficacy, self-regulation, and goal attainment, and whether these constructs mediated intervention effects on PA. Participants who received interventions with interpersonal strategies, compared to those who did not, increased their readiness (post-intervention), the self-regulation subscale of self-assessment, and goal attainment (post-intervention, 6-months). Participants who received interventions with intrapersonal strategies, compared to those who did not, increased their social support from family (post-intervention). There was no statistically significant mediation. To understand mechanisms through which interventions increase older adults' PA and to improve intervention effectiveness, researchers should continue to examine potential psychosocial mediators.Clinical Trial Registry: NCT02433249.

Enhancing the utility of the problem gambling severity index in clinical settings: Identifying refined categories within the problem gambling category.

BACKGROUND: The Problem Gambling Severity Index (PGSI) was intended for use in epidemiological research with gamblers across the continuum of risk. Its utility within clinical settings, where the majority of clients are problem gamblers, has been brought into question. AIMS: (1) Identify refined categories for the problem gambling category of the PGSI in help-seeking gamblers; (2) Validate these categories using the Gambling Symptom Assessment Scale (G-SAS); (3) Explore the relationship of these categories with indices of gambling and help-seeking behaviour. METHODS: Secondary data analysis of help-seeking problem gamblers from the Australian online gambling counselling/support service (Gambling Help Online [GHO]) from October 2012 to December 2015 (n = 5,881) and trial data evaluating an Australian online self-directed program for gambling (GamblingLess; n = 198). Both datasets included the PGSI, gambling frequency and expenditure. The GamblingLess dataset also included the G-SAS and help-seeking behaviour. RESULTS: A Latent Class Analysis, using GHO data, identified a 2-class solution. Multiple analytical methods identified a cut-off value of ≥ 19 distinguishing this 2-class solution (low problem severity: Median = 16; high problem severity: Median = 23). High problem severity gamblers had increased odds of being categorised in the higher GSAS category, greater gambling expenditure and having sought face-to-face support. The refined categories were not associated with gambling frequency, distance-based or self-directed help-seeking. CONCLUSION: These findings are consistent with a stepped-care approach, whereby individuals with higher severity may be better suited to more intensive interventions and individuals with lower severity could commence with less intensive interventions and step-up to intensive interventions.

Childhood obesity intervention studies: A narrative review and guide for investigators, authors, editors, reviewers, journalists, and readers to guard against exaggerated effectiveness claims.

Being able to draw accurate conclusions from childhood obesity trials is important to make advances in reversing the obesity epidemic. However, obesity research sometimes is not conducted or reported to appropriate scientific standards. To constructively draw attention to this issue, we present 10 errors that are commonly committed, illustrate each error with examples from the childhood obesity literature, and follow with suggestions on how to avoid these errors. These errors are as follows: using self-reported outcomes and teaching to the test; foregoing control groups and risking regression to the mean creating differences over time; changing the goal posts; ignoring clustering in studies that randomize groups of children; following the forking paths, subsetting, p-hacking, and data dredging; basing conclusions on tests for significant differences from baseline; equating "no statistically significant difference" with "equally effective"; ignoring intervention study results in favor of observational analyses; using one-sided testing for statistical significance; and stating that effects are clinically significant even though they are not statistically significant. We hope that compiling these errors in one article will serve as the beginning of a checklist to support fidelity in conducting, analyzing, and reporting childhood obesity research.

A quasi-experimental study of the impact of school start time changes on adolescents' mood, self-regulation, safety, and health.

OBJECTIVE: To determine whether school start time changes impact adolescents' mood, self-regulation, safety, and health. METHODS: In September 2015, two school start time changes were implemented in Fairfax County (VA) Public Schools: a 50-minute delay (to 8:10 am) for high schools and secondary schools and a 30-minute advance (to 7:30 am) for middle schools. We conducted cross-sectional surveys of students' sleep, mood, self-regulation, health, and safety before (2017 students) and after (1180 students) these changes. RESULTS: Adjusted for confounders, a 50-minute delay was associated with a decreased prevalence of low mood (-4.7%; 95% confidence interval [CI]: -8.2%, -1.2%), drowsy driving, (-8.4%; 95% CI: -15.9%, -0.9%), and skipping breakfast (-4.2%; 95% CI: -8.1%, -0.2%) but no other significant changes. There were no significant changes associated with a 30-minute advance. CONCLUSIONS: A 50-minute delay in school start time in high schools and secondary schools was associated with a decreased prevalence of low mood, drowsy driving, and skipping breakfast. A 30-minute advance in start time in middle schools was not associated with any appreciable changes.