Do Age, Race/Ethnicity, and Gender Moderate the Effectiveness of a Peer-Led Healthy Lifestyle Intervention for People with Serious Mental Illness in Supportive Housing?

Background and Purpose. People with serious mental illness (SMI, e.g., schizophrenia) die approximately 25 years earlier than the general population largely due to elevated rates of obesity, type-2 diabetes, and cardiovascular disease. Clinical trials in the U.S. have shown that healthy lifestyle interventions that increase healthy dietary habits and physical activity can improve the health of people with SMI, primarily through weight reduction. Yet, little is known about whether the effectiveness of these interventions differed by participants’ characteristics (e.g., age, gender). In this study, we used data from a NIMH-funded effectiveness trial of a peer-led healthy lifestyle intervention (PGLB) to examine whether participants’ age, racial/ethnic minority status, and gender moderated the treatment effects of PGLB in helping participants achieve clinically significant weight loss (i.e., at least 5% weight loss of baseline weight).

Methods. The trial was conducted in three supportive housing agencies, enrolled 314 participants with SMI who were overweight/obese (BMI > 25) and randomly assigned them to PGLB or usual care (UC). PGLB is a 12-month manualized healthy lifestyle intervention delivered by peer-specialists, people with lived experiences with SMI. Assessments were conducted at baseline, 6-, 12-, and 18-months post-randomization. The main outcome for these analyses were the proportion of participants achieving clinically significant weight loss. Mixed-effects regression models adjusting for study site, time, and baseline weight, were used to examine the interactions between treatment conditions (PGLB vs. UC) and participants’ age, race/ethnicity, and gender to determine whether these characteristics moderated the effectiveness of PGLB on clinically significant weight loss.

Results. Participants were mostly male (56%) and racial/ethnic minorities (81%), largely non-Hispanic blacks, with a mean age of 49 years (SD = 11.12). At baseline, participants had a mean BMI of 34 (SD = 7.18). The most common psychiatric diagnoses at baseline were major depression (76%), schizophrenia/schizoaffective disorder (59%), and bipolar disorder (48%). The most common medical conditions at baseline were hypertension (55%), high cholesterol (37%) and diabetes mellitus (34%). A larger proportion of PGLB participants than UC achieved clinically significant weight loss at 12- and 18-months, but these were not statistically significant. After adjusting for study site, baseline weight, and time, participants’ age (Odds Ratio [OR]=0.16, 95% CI 0.03, 0.77, p=0.02) and racial/minority status (OR=11.74, 95% CI 1.69, 81.50, p=0.01), but not gender (OR=0.72, 95% CI, 0.19,4.3, p=0.91), significantly moderated PGLB effects throughout this 18-months trial. Compared to UC, the probability of achieving clinically significant weight loss throughout this trial was significantly higher for PGLB participants who were 49 years or younger compared to those 50 years or older and for racial/ethnic minorities compared to non-Hispanic whites.

Conclusions and Implications. Our findings indicated that PGLB was most beneficial for participants who were younger and for racial/ethnic minorities in helping them achieve clinically significant weight loss. These differential treatment outcomes suggest that the impact of healthy lifestyle interventions for people with SMI may not be uniformed across this diverse population. More studies are needed to clarify why and how these interventions work for certain group versus others.