Background Comparing findings from separate trials is necessary to choose among treatment options, however differences among study cohorts may impede these comparisons. Purpose As a case study, to examine the overlap of study cohorts in two large randomized controlled clinical trials that assess interventions to reduce risk of major cardiovascular disease events in adults with type 2 diabetes in order to explore the feasibility of cross-trial comparisons Methods The Action for Health in Diabetes (Look AHEAD) and The Action to Control Cardiovascular Risk in Diabetes (ACCORD) trials enrolled 5,145 and 10,251 adults with type 2 diabetes, respectively. Look AHEAD assesses the efficacy of an intensive lifestyle intervention designed to produce weight loss; ACCORD tests pharmacological therapies for control of glycemia, hyperlipidemia, and hypertension. Incidence of major cardiovascular disease events is the primary outcome for both trials. A sample was constructed to include participants from each trial who appeared to meet eligibility criteria and be appropriate candidates for the other trial’s interventions. Demographic characteristics, health status, and outcomes of members and non-members of this constructed sample were compared. Results Nearly 80% of Look AHEAD participants were projected to be ineligible for ACCORD; ineligibility was primarily due to better glycemic control or no early history of cardiovascular disease. Approximately 30% of ACCORD participants were projected to be ineligible for Look AHEAD, often for reasons linked to poorer health. The characteristics of participants projected to be jointly eligible for both trials continued to reflect differences between trials according to factors likely linked to retention, adherence, and study outcomes. Limitations Accurate ascertainment of cross-trial eligibility was hampered by differences between protocols. Conclusions Despite several similarities, the Look AHEAD and ACCORD cohorts represent distinct populations. Even within the subsets of participants who appear to be eligible and appropriate candidates for trials of both modes of intervention, differences remained. Direct comparisons of results from separate trials of lifestyle and pharmacologic interventions are compromised by marked differences in enrolled cohorts.

In the SPRINT (Systolic Blood Pressure Intervention Trial), the number of strokes did not differ significantly by treatment group. However, stroke subtypes have heterogeneous causes that could respond differently to intensive blood pressure control. SPRINT participants (N=9361) were randomized to target systolic blood pressures of <120 mm Hg (intensive treatment) compared with <140 mm Hg (standard treatment). We compared incident hemorrhage, cardiac embolism, large- and small-vessel infarctions across treatment arms. Participants randomized to the intensive arm had mean systolic blood pressures of 121.4 mm Hg in the intensive arm (N=4678) and 136.2 mm Hg in the standard arm (N=4683) at one year. Sixty-nine strokes occurred in the intensive arm and 78 in the standard arm when SPRINT was stopped. The breakdown of stroke subtypes across treatment arms included hemorrhagic (intensive treatment, n=6, standard treatment, n=7) and ischemic stroke subtypes (large artery atherosclerosis: intensive treatment n=11, standard treatment, n=13; cardiac embolism: intensive treatment n=11, standard treatment n=15; small artery occlusion: intensive treatment n=8, standard treatment n=8; other ischemic stroke: intensive treatment n=3, standard treatment n=1). Fewer strokes occurred among participants without prior cardiovascular disease in the intensive (n=43) than the standard arm (n=61), but the difference did not reach predefined statistical significance level of 0.05 (P=0.09). The interaction between baseline cardiovascular risk factor status and treatment arm on stroke risk did not reach significance (P=0.05). Similar numbers of stroke subtypes occurred in the intensive BP control and standard control arms of SPRINT.

The SPRINT (Systolic Blood Pressure Intervention Trial) demonstrated reduced cardiovascular outcomes. We evaluated diabetes mellitus incidence in this randomized trial that compared intensive blood pressure strategy (systolic blood pressure <120 mm Hg) versus standard strategy (<140 mm Hg). Participants were ≥50 years of age, with systolic 130 to 180 mm Hg and increased cardiovascular risk. Participants were excluded if they had diabetes mellitus, polycystic kidney disease, proteinuria >1 g/d, heart failure, dementia, or stroke. Postrandomization exclusions included participants missing blood glucose or ≥126 mg/dL (6.99 mmol/L) or on hypoglycemics. The outcome was incident diabetes mellitus: fasting blood glucose ≥126 mg/dL (6.99 mmol/L), diabetes mellitus self-report, or new use of hypoglycemics. The secondary outcome was impaired fasting glucose (100-125 mg/dL [5.55-6.94 mmol/L]) among those with normoglycemia (<100 mg/dL [5.55 mmol/L]). There were 9361 participants randomized and 981 excluded, yielding 4187 and 4193 participants assigned to intensive and standard strategies. There were 299 incident diabetes mellitus events (2.3% per year) for intensive and 251 events (1.9% per year) for standard, rates of 22.6 (20.2-25.3) versus 19.0 (16.8-21.5) events per 1000 person-years of treatment, respectively (adjusted hazard ratio, 1.19 [95% CI, 0.95-1.49]). Impaired fasting glucose rates were 26.4 (24.9-28.0) and 22.5 (21.1-24.1) per 100 person-years for intensive and standard strategies (adjusted hazard ratio, 1.17 [1.06-1.30]). Intensive treatment strategy was not associated with increased diabetes mellitus but was associated with more impaired fasting glucose. The risks and benefits of intensive blood pressure targets should be factored into individualized patient treatment goals. Clinical Trial Registration - URL: http://www.clinicaltrials.gov. Unique identifier: NCT01206062.