Statistical analysis
REGRESSION
This study was designed with 90% power (α=0·05) to detect a common odds ratio (OR) of 0·8 for worse functional outcome at 6 months using ordinal logistic regression. This design required a sample size of 8360 patients from 110 sites, on the assumption that the distribution in the scores on the mRS in the usual care group would be similar to the control group who received standard less-intensive blood pressure lowering treatment in the INTERACT2 study,All analyses were undertaken at the patient level with adjustment for clustering. The main analyses were performed on a modified intention-to-treat basis by including all participants who provided written consent and had primary outcome data available, regardless of protocol adherence. The primary analysis was to be done using ordinal logistic regression with a random effect for cluster (hospital site), a fixed categorical effect of time (four periods), and a fixed effect indicating the group assignment of each cluster at each period. However, upon unmasking the data, we recognised that the trial did not conform to a standard stepped wedge design in which all clusters contemporaneously switch from one period to the next,We undertook a series of preplanned sensitivity analyses with various approaches to the imputation of missing values,We found the proportional-odds assumption was violated but the analyses proceeded on the understanding that the treatment effect was not constant across categories of the mRS. The result was complemented by a graphical assessment of shifts across categories using bar plots as well as binary analyses. As prespecified, the six subgroups for analysis were age, sex, country, NIHSS score (<15 Although two interim analyses were undertaken during the study period, given the use of a conservative Haybittle–Peto stopping rule