Twenty‐year progression of body mass index in a county‐wide cohort of people with schizophrenia and bipolar disorder identified at their first episode of psychosis

OBJECTIVE: There is an increased prevalence of obesity in schizophrenia and bipolar disorder, leading to a disproportionate risk of adverse health conditions. Prospective, long-term weight gain data, however, are scarce. METHODS: We analyzed data from the Suffolk County Mental Health Project cohort of consecutive first admissions with psychosis recruited from September 1989 to December 1995 and subsequently followed for 20 years, focusing on people with schizophrenia (n=146) and bipolar disorder (n=87). The time course of weight gain was examined using a 2 (group)×5 (time) mixed-model repeated measures ANOVA, and body mass index (BMI) scores at the first (6 months) and second (2 years) assessments were compared to examine whether early overweight predicted later obesity. RESULTS: There was a statistically significant effect of time (F(1,210)=68.06, P<.001) and diagnosis (F(1,210)=29.18, P<.001) on BMI, but not the interaction of time×diagnosis (F(1,210)=0.88, P=.48). Most participants had normal BMIs at the first two assessments. Early overweight was a predictor of eventual obesity for both groups. At the 20-year follow-ups, approximately 50% of the bipolar and 62% of the schizophrenia sample were obese, with a greater prevalence of obesity in schizophrenia at each assessment (all P<.02), except for years 4 (P=.12) and 20 (P=.27). CONCLUSIONS: Nearly two-thirds of the participants with schizophrenia and over half of those with bipolar disorder were obese 20 years after first hospitalization for psychosis, considerably higher than the rate for adults in New York State (27%). Early intervention may be required to prevent long-term consequences of obesity-related morbidity and mortality.