Megastudies improve the impact of applied behavioural science.

Policy-makers are increasingly turning to behavioural science for insights about how to improve citizens' decisions and outcomes1. Typically, different scientists test different intervention ideas in different samples using different outcomes over different time intervals2. The lack of comparability of such individual investigations limits their potential to inform policy. Here, to address this limitation and accelerate the pace of discovery, we introduce the megastudy-a massive field experiment in which the effects of many different interventions are compared in the same population on the same objectively measured outcome for the same duration. In a megastudy targeting physical exercise among 61,293 members of an American fitness chain, 30 scientists from 15 different US universities worked in small independent teams to design a total of 54 different four-week digital programmes (or interventions) encouraging exercise. We show that 45% of these interventions significantly increased weekly gym visits by 9% to 27%; the top-performing intervention offered microrewards for returning to the gym after a missed workout. Only 8% of interventions induced behaviour change that was significant and measurable after the four-week intervention. Conditioning on the 45% of interventions that increased exercise during the intervention, we detected carry-over effects that were proportionally similar to those measured in previous research3-6. Forecasts by impartial judges failed to predict which interventions would be most effective, underscoring the value of testing many ideas at once and, therefore, the potential for megastudies to improve the evidentiary value of behavioural science.

A 680,000-person megastudy of nudges to encourage vaccination in pharmacies.

Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, we conducted a megastudy. We randomly assigned 689,693 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination or to a business-as-usual control condition that received no messages. We found that the reminder texts that we tested increased pharmacy vaccination rates by an average of 2.0 percentage points, or 6.8%, over a 3-mo follow-up period. The most-effective messages reminded patients that a flu shot was waiting for them and delivered reminders on multiple days. The top-performing intervention included two texts delivered 3 d apart and communicated to patients that a vaccine was "waiting for you." Neither experts nor lay people anticipated that this would be the best-performing treatment, underscoring the value of simultaneously testing many different nudges in a highly powered megastudy.

Changes in Reimbursement to Emergency Physicians After Medicaid Expansion Under the Patient Protection and Affordable Care Act.

STUDY OBJECTIVE: We examine the effect of Medicaid expansion on reimbursement for emergency physicians' professional services. METHODS: We conducted a retrospective study using data from a national emergency medicine group in a sample of 50 emergency departments (EDs) from July 1, 2012, to June 30, 2015. We categorized facilities in 14 states into full-expansion (23), partial-expansion (17), and nonexpansion (10) categories based on pre-expansion Medicaid eligibility criteria for all adults. We used a difference-in-differences design to assess the effect of Medicaid expansion on provider reimbursement per visit. Secondary outcomes included reimbursement per relative value unit and relative value units per visit, both overall and by payer type, controlling for age, sex, billing codes, and health system relationship. RESULTS: We studied greater than 6.7 million ED visits during July 2012 to December 2015, 3.0 million pre-expansion and 3.7 million postexpansion. After adjusting for covariates, reimbursement per visit increased 6.3% (95% confidence interval 1.4% to 11.1%) in full-expansion relative to nonexpansion states and did not change significantly in partial-expansion versus nonexpansion states. Reimbursement per visit for commercial insurance increased 17.1% (95% confidence interval 9.9% to 24.2%) in full-expansion versus nonexpansion states. Reimbursement for self-pay visits increased 9.7% (95% confidence interval 3.7% to 15.7%) in full-expansion versus nonexpansion states. Changes in payments were driven by higher reimbursement per relative value unit; relative value units per visit declined slightly in full-expansion compared with nonexpansion states. CONCLUSION: In this sample, full Medicaid expansion increased payments for emergency physicians' professional services compared with reimbursement in nonexpansion states. Higher reimbursement was driven primarily by lower proportions of uninsured patients and increased reimbursement per visit for both commercially insured and self-pay patients in states with full Medicaid expansion.

The Effect of Medicaid Expansion on the Nature of New Enrollees' Emergency Department Use.

We examine changes in emergency department (ED) visit acuity and care intensity for uninsured patients who gained Medicaid insurance in 2014 under the Patient Protection and Affordable Care Act. We use 2013-2015 longitudinal patient visit-level data from 30 EDs across 7 states from an emergency medicine group. We examine changes in ED use by previously uninsured Medicaid patients and patients remaining uninsured who were repeat ED users (≥1 visit before and after expansion) using a propensity-score weighted approach with statistical machine learning to estimate the weights. Compared with those remaining uninsured in nonexpansion states, newly covered Medicaid patients in expansion states showed a 29% relative increase in hospital admissions and 32% increase in admissions for nonambulatory care sensitive conditions with no increases in care intensity. Obtaining Medicaid insurance increased the relative proportion of ED visits requiring hospital admission suggesting increased outpatient access for low-acuity conditions previously addressed with ED care.