Working Papers

Nudging Patients at Scale: Evidence from Text-message Appointment Reminders
with Pablo Celhay, Paul Gertler, and Tadeja Gracner.   nudges chronic diseases health services
Presentations: ASHEcon 2021, iHEA 2021, CHITA 2020.


We study how reminding high-risk patients of their upcoming preventative, primary care appointments impacts health behaviors. We use a natural experiment in Chile, where text-message appointment reminders were scaled up nation-wide over three years at public, primary care clinics. Our data come from national medical, medication, hospitalization, and mortality records and include over 300,000 patients, all recently diagnosed with type 2 diabetes and/or hypertension. We find that nudging patients to attend their preventative care appointments increases visits by 5 to 7%, results that are about half as large as published smaller-scale or efficacy trials. Our results increase to 9 to 11% after taking clinic-level compliance into account, where on average 53% of eligible patients were sent text-message reminders. This increase in primary care utilization translates into an 11% increase in health screening. Reminders also lead to a 42% improvement in anti-hypertensive medication adherence, which is largely attributed to patients having any active prescription. Last, SMS reminders lead to a 17% increase in cardiovascular hospitalizations coupled with a reduction in in-hospital mortality, suggesting an increase in referrals through primary care or timely care-seeking behavior of emergency and specialized health services. Our findings are particularly important for settings with a gate-keeping healthcare model, which is common in OECD countries. In this type of system, patients must first visit their primary care provider before being approved for tests, prescribed medication, or referred to speciality and hospital care. This paper shows that through intervening at the first step in the cascade of care, even a light touch intervention such as text-message reminders can have large and meaningful downstream impacts.

The Role of Discretion in Clinical Decision Making: Evidence from Thresholds
clinical decision-making chronic diseases health services
Presentations: UC Berkeley Health Policy Colloquium 2022, University of Copenhagen Health Economics Workshop 2022.


When a decision maker has discretion, such as a worker reporting their taxable income, threshold-based rules or policies can distort behavior. This has not been studied in the context of medicine where thresholds guide many important diagnosis and treatment decisions. I study the decision to diagnose and treat hypertension, defined as blood pressure of at least 140/90 mmHg. Hypertension is the single most important risk factor for cardiovascular disease, but diagnosis can be challenging because blood pressure is a noisy measure of risk and often overstated in clinic. Using bunching estimation and electronic health records from over 600,000 patients in Chile I find that providers round the blood pressure of up to 62% of patients who test near the threshold, using their discretion to turn a positive test for hypertension into a negative. This behavioral response leads to a more accurate classification of patients in terms of their cardiovascular risk, as measured by future hospitalizations. I find that discretionary decisions are consistent with heuristic thinking: among patients with identical test results, those with characteristics representative of high cardiovascular risk are less likely to be sorted below the diagnostic threshold. These results suggest that in the case of limited information, heuristic thinking and discretionary diagnosis can lead to more accurate decisions and to better patient outcomes, underscoring the importance of clinical skill in achieving an efficient and equitable allocation of health care.

Can a private health sector engagement program with social health insurance encourage pro-poor outcomes? Evidence from an impact evaluation in Kenya.
with Joshua Gruber, Paul Gertler, Ada Kwan, and Grace Makana Barasa.  clinical decision-making health services


Private health sector engagement has been suggested as a health reform component to reduce healthcare inequities in Sub-Saharan Africa, where populations with the most need seek the least care. We study the simultaneous supply- and demand-side effects of African Health Markets for Equity (AHME), a management intervention that aimed to improve the quality and accessibility of private-sector clinics in Kenya. AHME focused on access to public health insurance, where the government is the payer, as a mechanism to increase use of affordable, high-quality private care for poor individuals. The program was successful in increasing the share of clinics accepting national insurance, the share of households enrolled in national health insurance, and in turn the share of clinics' clients from lower wealth quintiles. Efforts to reduce the cost of care must also ensure that the quality of care is maintained. We conducted standardized patient (SP) experiments to measure the effects of not being able to afford full services on quality of care. SPs presented as poor by telling the provider they could only afford KSH 300 in fees. We find that when faced with a client with a budget constraint, providers reduced the quantity of both necessary and unnecessary care, resulting in lower quality of care for 'poor' clients. While public insurance is a promising mechanism to connect low-income households to private care, more work must be done to ensure clients of all wealth levels receive high quality care.

Increasing the intensity of physical education reduces student enrollment: evidence from synthetic difference-in-differences
with Nicole Perales. chronic diseases


Physical education mandates have been used to promote physical activity in the United States, where one in five adolescents are obese. However, previous research demonstrates mixed results in the effect of physical education on student health. We study the effects of two states' physical education policies that each increased the portion of high school physical education time devoted to moderate-to-vigorous physical activity from zero to 50\%. Using a synthetic difference-in-differences design and 17 years of Youth Risk Behavior Surveillance System national surveys, we find the policy has no effect on high school students' physical activity or body mass index on average, and led to a reduction of enrollment in physical education class. This reduction is larger in Idaho, which has no physical education requirement in high school, than in Texas where at least one unit is required. Non-white students, females, and students who watched television on weekdays were most likely to dis-enrol, suggesting that those who stood to gain the most from policy benefited the least by selecting selecting out of physical education once it became more physically demanding. We conclude that school-based physical education policies targeting the intensive margin risk unintended consequences on the extensive margin when physical education enrollment is voluntary.

In Progress

Sugar-rich diet in-utero and early childhood can lead to earlier onset of diabetes or hypertension
With Paul Gertler and Tadeja Gracner.  chronic diseases


Do private providers give patients what they demand, even if it is inappropriate? A randomised study using unannounced standardised patients in Kenya
BMJ Open 2022, A Kwan, CE Boone, G Sulis, P Gertler.  clinical decision-making health services


We use standardized patients to study the effects of a patient demanding one of two possible inappropriate medicines, as examples of trade-offs providers might make between risks, profits, and patient satisfaction. At private clinics in Kenya, demanding a deworming medicine significantly increased its rate of dispensing to 35% (95% CI: 25-44) compared to 3% (95% CI: 0-7) without demanding. Demanding an antibiotic did not change its probability of dispensing. These results show private providers appear to account for both business-driven benefits and individual health impacts when making prescribing decisions.

How Spillovers from Appointment Reminders Improve Health Clinic Efficiency
Journal of Health Economics 2022 and NBER Working Paper, CE Boone, P Celhay, P Gertler, T Gracner, J Rodriguez. nudges chronic diseases health services


Missed clinic appointments or no-shows burden health care systems through inefficient use of staff time and resources. Scheduling software combined with automatically sent appointment reminders shows promise to improve clinics’ management through timely cancellations and re-scheduling, but at-scale evidence is missing. We study a nationwide text message appointment reminder program in Chile implemented at primary care clinics for patients with chronic disease. Using longitudinal clinic-level data, we find that the program did not change the number of visits by chronic patients eligible to receive the reminder, but visits from other patients ineligible to receive reminders increased by 5.0% in the first year and 7.4% in the second. Clinics treating more chronic patients and those with a relatively younger patient population benefited more from the program. Scheduling systems combined with automatic appointment reminders were effective in increasing clinics’ ability to care for more patients, likely due to timely cancellations and re-scheduling.

StayWell at Home: A Text Messaging Intervention to Counteract Depression and Anxiety during COVID-19 Social Distancing
JMIR Mental Health 2021. Protocol. A Aguilera, R Hernandez-Ramos, A Haro, CE Boone, T Luo, J Xu, B Chakraborty, C Karr, S Darrow, CA Figueroa.   nudges


Background: Social distancing and stay-at-home orders are critical interventions to slow down person-to-person transmission of COVID-19. While these societal changes help to contain the pandemic, they also have unintended negative consequences, including anxiety and depression. We developed StayWell, a daily skills-based SMS text messaging program, to mitigate COVID-19 related depression and anxiety symptoms among people who speak English and Spanish in the United States.

Objective: This paper describes the changes in the anxiety and depression levels of participants in the StayWell program after 60 days of exposure to skills-based SMS text messages.

Methods: We used self-administered, empirically supported web-based questionnaires to assess the demographic and clinical characteristics of StayWell participants. Anxiety and depression were measured using the 2-item Generalized Anxiety Disorder (GAD-2) scale and the 8-item Patient Health Quesstionanire-8 (PHQ-8) scale at baseline and 60-day timepoints. We used paired t-tests to detect the change in PHQ-8 and GAD-2 scores from baseline to follow-up measured 60 days later.

Results: The analytic sample includes 193 participants who completed both the baseline and 60-day exit questionnaires. At the 60-day time point, there were statistically significant reductions in both PHQ-8 and GAD-2 scores from baseline. We found an average reduction of -1.72 (95% CI: -2.35, -1.09) in PHQ-8 scores and -0.48 (95% CI: -0.71, -0.25) in GAD-2 scores. This translated to an 18.5% and 17.2% reduction in mean PHQ-8 scores and GAD-2, respectively.

Conclusions: StayWell is a low-intensity, cost-effective, and accessible population-level mental health intervention. Participation in StayWell focused on COVID-19 mental health coping skills and was related to improved depression and anxiety symptoms. In addition to improvements in outcomes, we found high levels of engagement during the 60-day intervention period. Text messaging interventions could serve as an important public health tool for disseminating strategies to manage mental health. Clinical Trial: Identifier: NCT04473599

Proximate determinants of tuberculosis in Indigenous peoples worldwide: a systematic review
The Lancet Global Health 2019. M Cormier, K Schwartzman, DS N’Diaye, CE Boone, AM dos Santos, J Gaspar, D Cazabon, et al.


Background: Indigenous peoples worldwide carry a disproportionate tuberculosis burden. There is an increasing awareness of the effect of social determinants and proximate determinants such as alcohol use, overcrowding, type 1 and type 2 diabetes, substance misuse, HIV, food insecurity and malnutrition, and smoking on the burden of tuberculosis. We aimed to understand the potential contribution of such determinants to tuberculosis in Indigenous peoples and to document steps taken to address them.

Methods: We did a systematic review using seven databases (MEDLINE, Embase, CINAHL, Global Health, BIOSIS Previews, Web of Science, and the Cochrane Library). We identified English language articles published from Jan 1, 1980, to Dec 20, 2017, reporting the prevalence of proximate determinants of tuberculosis and preventive programmes targeting these determinants in Indigenous communities worldwide. We included any randomised controlled trials, controlled studies, cohort studies, cross-sectional studies, case reports, and qualitative research. Exclusion criteria were articles in languages other than English, full text not available, population was not Indigenous, focused exclusively on children or older people, and studies that focused on pharmacological interventions.

Findings: Of 34 255 articles identified, 475 were eligible for inclusion. Most studies confirmed a higher prevalence of proximate determinants in Indigenous communities than in the general population. Diabetes was more frequent in Indigenous communities within high-income countries versus in low-income countries. The prevalence of alcohol use was generally similar to that among non-Indigenous groups, although patterns of drinking often differed. Smoking prevalence and smokeless tobacco consumption were commonly higher in Indigenous groups than in non-Indigenous groups. Food insecurity was highly prevalent in most Indigenous communities evaluated. Substance use was more frequent in Indigenous inhabitants of high-income countries than of low-income countries, with wide variation across Indigenous communities. The literature pertaining to HIV, crowding, and housing conditions among Indigenous peoples was too scant to draw firm conclusions. Preventive programmes that are culturally appropriate targeting these determinants appear feasible, although their effectiveness is largely unproven.

Interpretation: Indigenous peoples were generally reported to have a higher prevalence of several proximate determinants of tuberculosis than non-Indigenous peoples, with wide variation across Indigenous communities. These findings emphasise the need for community-led, culturally appropriate strategies to address smoking, food insecurity, and diabetes in Indigenous populations as important public health goals in their own right, and also to reduce the burden of tuberculosis.

Funding: Canadian Institutes of Health Research.

Zika: A scourge in urban slums
PLOS Neglected Tropical Diseases 2017. RE Snyder, CE Boone, CA Araújo Cardoso, F Aguiar-Alves, F Neves, LW Riley.
Commentary piece