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The Impact of Employee Wellness Programs: A Randomized Controlled Trial
Last registered on January 05, 2021


Trial Information
General Information
The Impact of Employee Wellness Programs: A Randomized Controlled Trial
Initial registration date
February 03, 2015
Last updated
January 05, 2021 12:52 AM EST

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Primary Investigator
Harvard Medical School
Other Primary Investigator(s)
PI Affiliation
University of Chicago Harris School of Public Policy
PI Affiliation
Harvard Medical School
Additional Trial Information
On going
Start date
End date
Secondary IDs
Health care costs are a major concern for policymakers, patients, and employers. Many employers across the United States are implementing or considering employee wellness programs in an effort to control costs while improving employee productivity and health. The Affordable Care Act also established a variety of incentives for employee wellness. Despite the popularity of wellness programs, little rigorous evidence exists on their effects on health, productivity, and health care costs or utilization. Such evidence is crucial for employers and policymakers alike.

We will evaluate the effect of a year-long employee wellness intervention at a large multi-state firm in the Eastern United States, using a randomized controlled trial design. The wellness intervention will consist of several components, including team-based wellness challenges, nutrition counseling, stress reduction, and individual-focused physical activity. The intervention has been designed with and will be fielded through an experienced and large-scale vendor.

Randomizing this intervention across a set of treatment and control sites, we will evaluate its impact on 5 categories of outcomes gathered from both primary and administrative data sources: (1) self-reported health and well-being, (2) biometrics (such as body mass index, blood pressure, cholesterol, and blood sugar), (3) worker absenteeism and turnover, (4) health care spending and utilization, and (5) return on investment. Better information about the effectiveness of such programs should inform both employer investment and public policy.
External Link(s)
Registration Citation
Baicker, Katherine, Zirui Song and Zirui Song. 2021. "The Impact of Employee Wellness Programs: A Randomized Controlled Trial." AEA RCT Registry. January 05. https://doi.org/10.1257/rct.586-6.6.
Former Citation
Baicker, Katherine et al. 2021. "The Impact of Employee Wellness Programs: A Randomized Controlled Trial." AEA RCT Registry. January 05. http://www.socialscienceregistry.org/trials/586/history/83411.
Sponsors & Partners

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Experimental Details
We will evaluate the effect of a two and a half year employee wellness intervention at a large multi-state firm. The intervention is based on a multi-part platform implemented by an established vendor, including a pre-intervention and post-intervention personal health assessment along with regular screenings. The staged program components include individual nutrition coaching, disease management, stress-reduction (using behavioral health coaching), and a team-based wellness challenge (capitalizing on social supports to improve diet and exercise).
Intervention Start Date
Intervention End Date
Primary Outcomes
Primary Outcomes (end points)
Summary of outcome measures

1. Self-Reported Health and Behavior

Source: Surveys
Outcomes: Self-reported physical and mental health; anxiety and stress; satisfaction with care; life satisfaction and happiness; level of physical activity; healthful behavior; disease diagnosis and management

2. Clinical Health

Source: Surveys
Outcomes: Mental health (depression, anxiety); Diagnoses

Source: Biometric Assessments
Outcomes: Blood assays (total & HDL cholesterol, HbA1c); Blood pressure; BMI (height and weight)

3. Employment and Productivity

Source: Employment Records
Outcomes: Productivity (absenteeism; job performance evaluations; promotion), Employment (hours worked; wages/salary; retention and employment tenure)

Source: Surveys
Outcomes: Satisfaction with employment; on-the-job stress

4. Health Care Utilization and Spending

Source: Insurance Claims Data
Outcomes: Spending and utilization overall and by category of care (inpatient, outpatient, emergency department, prescription drugs, preventive); and condition (chronic diseases, mental health)

5. Return on Investment

Comparison of complete program costs to monetized benefits

Primary Outcomes (explanation)
Outcomes will be collected for all employees at treatment and control worksites (including both program participants and non-participants).
Secondary Outcomes
Secondary Outcomes (end points)
Secondary Outcomes (explanation)
Experimental Design
Experimental Design
The study design centers on the random assignment of employer worksites to treatment and control arms. The wellness intervention will be implemented in treatment arm sites, while control arm sites will operate as usual. Primary data will be collected from all employees (program participants and non-participants) at both treatment and control arm sites in parallel. This random assignment will allow causal inferences about the effect of the intervention on a range of outcomes.
Experimental Design Details
Not available
Randomization Method
The employer has approximately 200 worksites. We will first eliminate the fewer than 20% of worksites that are geographically difficult to reach for researchers or have atypical insurance coverage. We then randomly assigned 25 of the worksites to the treatment arm and 25 to the control arm for primary data collection. Additional secondary data will also be collected from all worksites.
Randomization Unit
Was the treatment clustered?
Experiment Characteristics
Sample size: planned number of clusters
50 worksites for primary data and secondary data (25 treatment and 25 control)
120 worksites for additional secondary data
Sample size: planned number of observations
Primary data: 14,000 employees; Secondary data: additional 34,000 employees.
Sample size (or number of clusters) by treatment arms
Primary data will be collected from 50 randomly assigned worksites (25 sites in the treatment arm and 25 sites to the control arm), with about 100 employees at each site at any given time. Additional data will be collected from secondary sources for these 50 plus approximately 120 additional sites.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
IRB Name
Harvard University
IRB Approval Date
IRB Approval Number
Analysis Plan
Analysis Plan Documents
BJs-WW-Harvard Analysis Plan Phase 1 Final 2018-3-15

MD5: ea81b63023c64dcf018ccfea42252c54

SHA1: 2eea07b79e3c72dc40f9f99fb97f03983fbdc43c

Uploaded At: March 15, 2018

Analysis Plan Phase 2 Final 2020-1-7

MD5: dd129556dd943ad78fd2485155a55111

SHA1: 9f2b08f44a7511fc6608fa6678bab4639356961a

Uploaded At: January 09, 2020