> I didn't read the study, but did it control for weight, smoking and alcohol/drug use? Smoking rates are much higher in people with schizophrenia than in the general population, as are obesity rates (in part because of drugs like clozapine) and alcohol/drug abuse.
Baseball55,
I don't understand statistics very well, but here's what the authors of the report wrote about the statistical analysis that they did:
"This study examined time to development of diabetes mellitus and death from cardiovascular disease associated with clozapine treatment at 12-month intervals over a 10-year period. Baseline and follow-up descriptive statistics were tabulated. Weight, serum cholesterol level, and serum triglyceride level were treated as continuous and analyzed by means of longitudinal methods. The Cox proportional hazards regressions were used to test the association between the covariates (age, ethnicity, BMI, total cholesterol level, serum triglyceride level, systolic and diastolic blood pressure, smoking, and diabetes mellitus) and death from cardiovascular disease and the development of diabetes mellitus. Age, race, and gender were analyzed as baseline covariates, and BMI, total cholesterol level, clozapine total daily dose, serum triglyceride level, and weight were analyzed as time-dependent covariates. Each covariate was analyzed separately.
"Time was used as a stratum and ties were handled with the discrete option in the SAS PHREG procedure (SAS Institute Inc., Cary, N.C.). This replaces the proportional hazards model with the discrete logistic model so that odds ratios rather than hazard ratios are computed. The Kaplan-Meier estimate of time to development of diabetes mellitus and cardiovascular death were computed. Changes from baseline weight, BMI, total cholesterol level, and serum triglyceride level were analyzed using a mixed-effects model. This model has fixed linear term for time and random intercept and linear term for time for each patient. The fixed effects estimate the mean trajectory of the change from baseline, and the random effects allow a separate trajectory for each patient. All p values are 2-tailed, and a p value < .05 was considered evidence for statistical significance."
So, if I'm understanding things correctly, it looks like the researchers factored weight, smoking, and some other risk factors for cardiovascular disease-related death into their statistical analysis. I didn't see any mentions of alcohol use or the use of marijuana or "harder" recreational drugs, though. As far as I can tell, the researchers looked at how the measures of various risk factors for cardiovascular disease (obesity and cigarette smoking being among them) in the clozapine-treated patients changed over the course of the 10-year study period, in addition to examining the rates and estimates of diabetes mellitus and cardiovascular disease-related mortality in the patients.
Tomatheus
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