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Trends in the management of risk of diabetes complications
Hosnah Agban, C. Raina Elley, Tim Kenealy, Elizabeth Robinson
School of Population Health, University of Auckland, New Zealand
Aims: To assess changes over two years in the health status and management of a cohort of people with Type 2 diabetes from different ethnic groups within a primary care diabetes annual review programme in New Zealand.
Methods: The study evaluated changes in clinical measures and proportions achieving guideline targets for 7782 people who had data recorded at baseline in 2002–2003 and at follow-up two years later within the diabetes programme.
Results: A large proportion of Maori (47%) and Pacific (69%) patients had poor glycaemic control at baseline and only small improvements were made over the two years. Significant improvements were made in all the ethnic groups in blood pressure and lipid management at two-year follow-up. By the two-year follow-up, over 75% of Maori and Pacific patients received appropriate treatment with anti-hypertensive and lipid lowering medication and many of the ethnic disparities in risk factors for complications were reduced.
Conclusions: Participation in the annual reviewprogrammemay have contributed to improvements in clinical management and reduced disparities in a cohort with Type 2 diabetes.
However, the removal of restrictions on statin use in 2002, and introduction of diabetes management guidelines in 2003 may also have improved management standards.
© 2008 Primary Care Diabetes Europe. Published by Elsevier Ltd. All rights reserved.
There is a global epidemic of Type 2 diabetes and cardiovascular disease, and Type 2 diabetes is a major cause of preventable morbidity and mortality worldwide. [1]. Limiting the complications of diabetes is a national health priority in New Zealand [2]. as is reducing ethnic disparities in health outcomes across a wide range of diseases [3].
New Zealand has a diverse mix of ethnic groups. In the 2006 census, Europeans comprised 67.6% of the population. Maori,the indigenous people of New Zealand, made up 14.6%, Pacific peoples (mostly of Samoan, Tongan, Niuean and Cook Islands origin) made up 6.9% and Asians made up 9.2% (Chinese and Indians are the largest subgroups within the ‘Asian’ category) [4]. The 2002–2003 New Zealand Health Survey of people over fifteen years of age estimated that the self-identified prevalence of diagnosed diabetes within each ethnicity was as follows: Maori 8.0%, Pacific 10.1%, Asian 8.4% and European (including ‘Other’) 2.9%, so disparities in prevalence exist [5].Ethnic disparities have also existed in the management and complications of diabetes in New Zealand [6].
Type 2 diabetes is largely managed in primary health care in New Zealand [7]. Patients in NewZealand have traditionally
paid all or part of the cost for primary health care services. In the years since 2000 there have been several potentially important changes in diabetes care delivery in primary care. First, between 2000 and 2003, the government rolled out a nationwide diabetes annual review programme that was open to all people with diabetes and was fully subsidised, i.e. free to the patient [8]. It was presumed that systematic data collection at an annual review would lead to improved patient care.
The data would also be collated regionally and nationally to aid with monitoring and planning diabetes services. Second, new guidelines on management of cardiovascular risk and guidelines on the management of Type 2 diabetes were released
in December 2003 in New Zealand [9]. Third, in April 2002 the national pharmaceutical funding regulatory body (PHARMAC)
made HMG-CoA reductase inhibitors (statins) much more available on prescription by general practitioners [10].
We aimed to assess whether management of risk of diabetes complications improved in a cohort of patients who attended the primary care annual reviews over a two-year period between 2002 and 2005, within the wider context of improved access to statins and new diabetes guidelines. We were also interested to see if ethnic disparities reduced.
1. Methods
The study used data that were collected in structured annual reviews in routine primary health care and collated within 15
primary care organisations or diabetes trusts in New Zealand. Each individual in the dataset had a unique but anonymous
identifier. The study was approved by the New Zealand Multi-Regional Ethics Committee in 2004, no.: WGT/04/09/077.
1.1. Study participants
Eligible patients were identified from the primary care annual review data. Inclusion criteria were diagnosis of Type 2 diabetes,had undertaken an annual review in 2002 or 2003, and had a follow-up review two years later. A review qualified as
a two year follow up if it occurred between 21 months and 27 months after the baseline visit.
1.2. Outcome measures
Demographic variables collected included ethnicity, socioeconomic status deprivation score (NZDep2001) [11], gender,
age, and duration of diabetes. Outcome measures included current smoking status (yes/no), body mass index, systolic
and diastolic blood pressure, serum glycated haemoglobin (HbA1c), fasting total cholesterol, high-density lipoprotein
(HDL) and current treatment with blood pressure and lipid lowering medications.
Ethnicity codes were recorded in primary care, based on patient self-identity and were classified and grouped for analysis
according to standards set by Statistics New Zealand [12]. Ethnic categories in this study were European, Maori,
Pacific, Asian, Indian (of South Asian origin) and ‘Other’ (which included Middle Eastern, Latin American/Hispanic and
African).
In New Zealand, the New Zealand Deprivation Index (NZDep01) is commonly used as ameasure of deprivation and socioeconomic status. Data from the New Zealand 2001 census are used to create a composite measure of deprivation for each small area in New Zealand, based on income, employment status, home ownership, transport, communication, education, and living space [11]. There are ten NZDep2001 categories (deciles). For this study, NZDep2001 deciles were aggregated into quintiles 1–5, with quintile 1 being the least-deprived and quintile 5 being the most-deprived.
1.3. Guidelines targets
Clinical targets were set in the New Zealand 2003 guidelines to guide primary care physicians in the management of their
patients with Type 2 diabetes [9]. These targets included HbA1c of 7% or less; blood pressure 130/80mmHg or less; and fasting serum total cholesterol:HDL ratio of less than 4.5. According to the guidelines, obesity is defined as a bodymass index of 32 or greater for Maori and Pacific people and 30 or greater for all other ethnic groups [13]. The previous New Zealand guidelines recommended an HbA1c target of 7% but did not specify blood pressure or cholesterol targets [14].
1.4. Analyses
A two-tailed paired t-test was used to compare means, and a McNemar Chi-Square was used to compare paired proportions. All analyses were performed using STATA version 9.2 [15]. Analyses included only available data and missing values were not imputed.
2. Results
During 2002 and 2003, 42,321 patients with Type 2 diabetes had one or more annual review. Of these, 31,542 (75%) had at least one further annual review over the following three years. Of these, 8387 had a review approximately two years later. Four were missing gender data and a further 601 had missing or inconsistent data on ethnicity, leaving 7782 patients (18.4% of 42,321) who formed the cohort for this study. We compared data at the baseline visit between the 7782 in this cohort and the 34,539 patients who did not have a review two years later.
There was no significant difference by gender (p = 0.16) or in proportions in each ethnic group (p = 0.22). Mean age of the
study cohort was 64.3 (S.D. 12.1) compared with 62.5 (S.D. 13.3) for the others (p < 0.001). Mean HbA1c of the study cohort was 7.54% (S.D. 1.6) compared with 7.45% (S.D. 1.7) for the others (p < 0.001).
Table 1 – Baseline characteristics of patients with Type 2 diabetes at annual review in 2002 or 2003 by ethnicity n = 7782)
Variables European Maori Pacific Asian Indian Other
Number n (%) 5260 (67.6) 842 (10.8) 1,192 (15.3) 199 (2.6) 190 (2.4) 99 (1.3)
Female n (%) 2568 (48.8) 466 (55.3) 661 (55.5) 95 (47.7) 81 (42.6) 42 (42.4)
Age, years mean (S.D.) 67.5 (11.2) 57.8 (11.4) 57.0 (10.6) 59.6 (11.2) 56.0 (10.4) 60.7 (12.0)
Most deprived quintile n (%) 1127 (21.5) 488 (58.1) 956 (80.5) 36 (18.2) 60 (32.1) 31 (31.3)
Years known diabetes mean (S.D.) 6.8 (6.9) 7.1 (7.2) 6.9 (6.6) 5.7 (5.4) 5.8 (6.4) 7.4 (7.3)
Table 1 shows the characteristics of the study population by ethnic group. Table 2 shows changes between baseline and
follow up two years later. Overall, there was a small decrease in the proportions of patients achieving the target glycaemic
level specified in the guidelines (HbA1c of 7% or less) at the two-year follow up (n = 3716, 47.9%) compared with baseline
(n = 3984, 51.7%) (p < 0.001). Even so, there were improvements in mean HbA1c in most ethnic groups and significantly fewer with very poorly controlled diabetes (HbA1c > 8%) in Pacific and Indian patients (Table 2; Fig. 1). Proportions smoking decreased in all groups and obesity rates decreased for all except Asians; although not all changes were statistically significant (Table 2).
By the two-year follow-up, there was a decrease in the mean systolic and diastolic blood pressure in all ethnic groups (Table 2) and an increase in the proportion of patients with blood pressure at or below the recommended target
(130/80mmHg or less). Similarly, in all groups the mean total cholesterol declined and the mean HDL increased. For both
blood pressure and cholesterol measures, Table 2 indicates which changes were statistically significant.
Over the two years, there was an increase in the proportion of patients using anti-hypertensive and lipid lowering medications across all ethnic groups (Table 3). The proportions of patients on lipid lowering therapy in the Maori and ‘Other’
groups nearly doubled from baseline to the two-year follow up, while it tripled for Pacific patients.
3. Discussion
This study compared cross-sectional and individual twoyear
follow-up data in a cohort of people with Type 2 diabetes receiving structured annual diabetes reviews. All ethnic groups showed a decrease over the time period in the number of people with HbA1c greater than 8 mmol/L. There were also improvements in mean blood pressure and cholesterol measures, proportion of smokers, and proportion on anti-hypertensive or statins when their blood pressure or lipids, respectively, were outside guideline targets. In most instances the ethnic groups with the worst initial figures showed most improvement. There was also a trend towards reduced ethnic disparities in cardiovascular risk parameters and management, in particular. These changes occurred in the context of a primary care annual diabetes review program and after the release of new diabetes management guidelines and improved access to prescribing statins. It is not possible to determine how much each of these initiatives contributed to the improvements, if at all. However, these are encouraging findings.
Earlier research has shown that, compared with Europeans, Maori and Pacific people with Type 2 diabetes are younger at
diagnosis, more likely to be obese and more likely to smoke and have poorer glycaemic control [16,17]. Similarly, the Translating Research into Diabetes Study in the United Stated found that Asian/Pacific Island people and Latinos had poor glycaemic control compared with Whites (mean HbA1c 8.1% vs. 7.7%, p < 0.001) [18]. The difficulty in achieving glycaemic control over the two years in the current study may have been partly due to the tendency for HbA1c to deteriorate over time
with progression of the disease. Similar findings were reported in the three year cohort of the patients of South Island,
New Zealand where the percentage of well-controlled patients went from 56.1% to 50.2% between 2001 and 2005 [17], and in the six year cohort of the National Health and Nutrition Examination Survey (NHANES), USA (44.5% to 35.8% from 1988 to 1994) [19]. However, improvements can be achieved as shown by the Swedish Diabetes register, which reported a significant increase in the proportion of patients with good glycaemic control over time (65.6% to 70.9% from 1996 to 1999) [20].
In the current study, there were increases in the proportion receiving preventive cardiovascular treatment of anti-hypertensive and lipid-lowering therapy, and these were greatest among Pacific and Maori patients. The high rates
of blood pressure and lipid lowering medication rates have been found in other recent studies of diabetes management
in New Zealand primary health care [17,21]. The changes in medication use in the current study were accompanied
by improvements in blood pressure, particularly in Pacific, Maori and European patients, and in total cholesterol and
HDL cholesterol levels for all ethnic groups. Large increases in the proportion receiving lipid-lowering therapy in particular
were seen over the two years. These changes may be related to the full funding of statins and removal of prescribing
requirements by the New Zealand Pharmaceutical Management Company (PHARMAC) in 2002 [10]. PHARMAC’s
2003 annual review reported a 65% increase in statin prescribing from 2002 [10]. The United Kingdom Prospective Diabetes Study also reported an improvement in lipid parameters for all the ethnic groups studied over the nine-year cohort but deemed the changes not related to lipid lowering therapy [22].
A strength of this study was the inclusion of relatively large numbers of ethnic minority groups, including Maori,
Pacific, Asian and ‘Other’ people when compared with previous studies in the United Kingdom [22] and New Zealand.
[17]. In addition, there are fewstudies examiningmanagement trends of patients with Type 2 diabetes in primary health care.
VISIT WEBSITE OF AUTHOR OF THIS PAPER TO VIEW TABLE 2
However, therewere some variables missing and there may have been some recording error as the data were routinely collected and could not be validated at practice level as data were anonymysed before being collected for analysis. This study examined what has happened within one particular cohort of those that were both enrolled in the diabetes programme
and also attended two years later. The trends identified may not be generalisable to others in the programme or to other
settings. It is possible, perhaps likely, that those who enrolled and remained with the programme are not typical of all those
with diabetes in New Zealand. Nevertheless, it remains true that overall results were better for this group after two years,
in a condition that has a natural history of deterioration.
The study does provide some indication of trends with most parameters improving over time. In some instances, these trends were starting to address some of the ethnic disparities in risk factors and standards of care. Positive improvement in controlling risk factors is associated with a decrease in the progression to long-term diabetes complications [23,24]. However, there are ethnic variations in the rates of participation in the annual review programme throughout New Zealand [25]. The Ministry of Health estimates that 63% of Europeans, 27% of Maori, and 92% of Pacific people with diabetes had a free annual check in 2004 [25,26]. Therefore, disparities in access to the programme still exist.
The results of this study suggest that regular participation in a systematic and fully funded Diabetes programme in primary
health care may be associated with improving rates of good management in people with Type 2 diabetes and some
reduction in ethnic disparities. However, the study design was observational andwe cannot infer causality. Furthermore, it is
impossible to determine how much was associated with the programme and how much was associated with the release
of the management of Type 2 diabetes guidelines and the improved access to statins, or to other initiatives in the community at the time. There is also still room for improvement, particularly in glycaemic control and a representative study of trends over time is needed.
Conflict of interest
The individual authors of the study declare that they have no conflict of interest.
Acknowledgment
The authors would like to acknowledge the support of New Zealand Health Research Council (HRC) in funding the data
collection.
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Article history:
Received 6 November 2007
Received in revised form
27 March 2008
Accepted 7 August 2008
Published on line 30 September 2008
Published on this website on Thu, 04 Nov 2010