In August 2010, data were collected from 100 of the 101 practices in Tower Hamlets and Newham. One practice declined participation. Over the 3 years of the study, a total of 28 041 people in the study age range were identified as having type 2 diabetes in 2007 and 17 670 (63%) had an HbA1c recording in 2007. Of these 17 670 people, 8864 (50%) had uncontrolled diabetes (HbA1c>7.5%) of whom 42% were white, 50% were black African/Caribbean and 53% were south Asian. Among the 8864 uncontrolled patients, 6464 (73%) also had HbA1c values in 2008 and 2009. Of those excluded because of missing HbA1c records, 30% were white, 25% south Asian and 27% black African/Caribbean people; 27–28% were in each social deprivation group. Finally 207 (3%) people were excluded because they had missing treatment information in one or more years and 153 (2%) did not fit into any of the cohort treatment categories described in the methods.
The final sample therefore consisted of 6104 (68.9%) of the 8864 people with uncontrolled diabetes HbA1c >7.5%. Of these, 6017 (99%) had ethnicity recorded, 6087 (>99%) people had Townsend score recorded. Age and sex was recorded in everyone and serum cholesterol in 95% and BMI in 94%. In total there were 1101 (18%) white, 3785 (63%) south Asian, 993 (16%) black African/Caribbean and 160 (3%) other ethnic groups in the sample. Only 2% of people fell in the two least deprived quintiles, so the least three quintiles were combined and categorised as ‘Least’ deprived (N=1204, 20%), ‘High’ deprivation if they were in the most deprived quintile (N=1858, 31%) and ‘Medium’’ (N=3025, 50%) otherwise.
describes the variable mean or percentage in each category for each demographic group. describes the HbA1c mean and proportion of HbA1c control for each demographic group. Baseline HbA1c and the diabetes duration distribution were similar between ethnic groups. After 1 and 2 years mean HbA1c decreased in each ethnic group but the mean reduction in HbA1c from baseline was less in south Asian patients than other ethnic groups and these patients had the least chance of achieving HbA1c controlled to 7.5% or less. A similar proportion of each ethnic group fell into each deprivation category.
Altogether, 7% of patients remained on ‘Metformin Only’ for the whole study, 46% on ‘Combined Oral’ and 33% on ‘Insulin’. Treatment intensity increased in 15% of patients during the study. Despite similar baseline HbA1c, treatment categories between ethnic groups differed significantly (p<0.001); there was a greater proportion of south Asian people on ‘Combined Oral treatment’ 50% than white 35% or black African Caribbean 44% and a greater proportion of south Asian 80% and black African/Caribbean people 79% started and remained on more intensive treatment (either Combined oral or insulin) than white 75%.
Fewer south Asian people, 36% started or changed to insulin compared to black African/Caribbean 42% and white people 49%. A subanalysis indicated white people were significantly more likely to increase their treatment intensity 30%, than south Asian 19% and black people 22% (p<0.001).
describe the statistical models to estimate CfB HbA1c and HbA1c control. Person, practice and PCT were all significant (p<0.001) and were included in the final models. Baseline HbA1c, age, serum cholesterol, ethnicity, sex and cohort treatment had a significant effect on CfB HbA1c and HbA1c control. Townsend category and BMI were not significant but were retained in the models as variables of interest. The ethnicity×treatment and ethnicity×year interactions were not significant and were not included in either model.
Statistical model parameter estimates
In people with uncontrolled HbA1c at baseline, after 1 and 2 years on treatment; south Asian people had 0.15% less reduction in mean HbA1c than white people (p=0.005) and white people were 1.6 times (p<0.001) as likely to achieve HbA1c control relative to south Asian people. White and black African/Caribbean people had no significant difference in CfB HbA1c (p=0.705) or HbA1c control achievement (p=0.460). There was no evidence that social deprivation affected HbA1c reduction or HbA1c control achievement.
The ethnicity×treatment interaction was not significant, indicating that in each of the different treatment groups, south Asian people had the smallest reduction in HbA1c and the lowest probability of achieving HbA1c control after 1 and 2 years. This also indicates white and black African/Caribbean people have a similar response to each treatment. The ethnicity×diabetes duration interaction was not significant, indicating that south Asian people have the smallest reduction in HbA1c and probability of achieving HbA1c control when their duration of diabetes is between 0 and 2 years and more than 2 years.
illustrates that for an individual with HbA1c 9% at baseline on ‘Metformin Only’ and ‘Insulin’ treatments, that south Asian people had the least reduction in HbA1c for each treatment.
Expected HbA1c for each ethnic group on ‘Metformin Only’ and ‘Insulin’ treatment.
There was little variation in the distribution of subcategories in the ‘Combined Oral’ treatment between ethnic groups (). Most noticeably, white people were the most likely to intensify 20%, followed by black African/Caribbean people 18% and south Asian people 17%.
Combined oral treatment subcategories