12 months before and after switching from NPH to glargine (A), mean change in HbA
after switch (B), use of bolus insulin before and after switch (C) and total daily insulin dose before and after switch (D) (unadjusted data). The last measurement for NPH is at -3 months (indicated by vertical dotted line). During period -12 m to -3 m patients are taking NPH only. During 3 month switch time point (0 months) patients may be prescribed NPH or glargine. During period +3 m to +12 m patients are only prescribed glargine. Linearly interpolated data were used to graphically depict the change in each parameter. Linearly interpolated data affords a clearer graphical interpretation but may bias estimates of variance; as such error bars (95% confidence intervals for the means) are not reported. Total daily insulin dose was calculated according to the number of units prescribed divided by the number of days covered by the prescription.