Risk factors for complications of type 1 diabetes: A nationwide comparison

Including a comparison with the general population Eleanor J Hothersall1 on behalf of the Scottish Diabetes

Research Network Epidemiology Group*

1 University of Dundee

AcknowledgementsThis work was supported by the Wellcome Trust through the Scottish Health Informatics Programme (SHIP) Grant (Ref WT086113). SHIP is a collaboration between the Universities of Aberdeen, Dundee, Edinburgh, Glasgow and St Andrews and the Information Services Division of NHS Scotland

*The Scottish Diabetes Research Network Epidemiology Group Members involved in this study were Helen M. Colhoun, Shona Livingstone, Eleanor Hothersall, Helen Looker, Sarah Wild, Robert Lindsay, John Chalmers, Stephen Cleland, Graham Leese, John McKnight, Andrew Morris, Donald Pearson, Norman Peden, John Petrie, Sam Phillip, Naveed Sattar and Frank Sullivan. Poster produced with assistance from Shona Livingstone and Professor Helen Colhoun

References1. . Orchard TJ et al. (2006) Type 1 Diabetes and Coronary Artery Disease. Diabetes Care 29: 2528-2538.2. Soedamah-Muthu SS, et al. (2006)High Risk of Cardiovascular Disease in Patients With Type 1 Diabetes in the U.K.: A cohort study using the General Practice Research Database Diabetes Care 29 (4) p. 798-804.3. Wannamethee S, et al. (2011) Do women exhibit greater differences in established and novel risk factors between diabetes and non-diabetes than men? The British Regional Heart Study and British Women's Heart Health Study. Diabetologia DOI 10.100.4. Colhoun HM, et al. (1999) The scope for cardiovascular disease risk factor intervention among people with diabetes mellitus in England: a population-based analysis from the Health Surveys for England 1991-94 Diabetic Medicine 16 (1) p. 35-40.5. Scottish Intercollegiate Guidelines Network (2010) SIGN 116: Management of Diabetes. A national clinical guideline http://www.sign.ac.uk/pdf/sign116.pdf Accessed:14th April 2012.6. The Scottish Government (2009) The Scottish Health Survey 2008 Edinburgh, The Scottish Government.7. The Diabetes Control and Complications Trial Research Group (1993) The Effect of Intensive Treatment of Diabetes on the Development and Progression of Long-Term Complications in Insulin-Dependent Diabetes Mellitus. New England Journal of Medicine 329: 977-986.8. Nathan DM, Cleary PA, Backlund J-YC, Genuth SM, Lachin JM, et al. (2005) Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes. New England Journal of Medicine 353: 2643-2653.9. American Diabetes Association (2011) Standards of Medical Care in Diabetes—2011. Diabetes Care 34: S11-S61.

BackgroundType 1 diabetes (T1DM) is associated with an elevation in the risk of cardiovascular disease (CVD) and all-cause mortality1, with higher relative risks of cardiac events in women than men with diabetes2. Explanations for this are unclear, but one hypothesis is that rates of risk factors are higher in women than men. Few studies exist comparing rates of risk factors in T1DM with the general population3,4.

We compared risk factor prevalence (smoking, obesity, hypertension, raised cholesterol and poor glycaemic control) and attainment of risk factor target levels5 in the T1DM population with published data from the Scottish Health Survey6

(SHS), an annual representative survey of the general population of Scotland.

Table 1. Risk factors in population age 16+ with T1DM (age standardised) and general population6.     T1DM (95% CI) General

population(95% CI)

Current smoker (%)

Men 27.5 (26.7, 28.3) 27.0 (25,28.6)

Women 22.3 (21.4, 23.1) 25.0 (23.5, 26.5)*BMI ≥30 (%) Men 22.4 (21.6, 23.1) 26.0 (24.3, 27.7)*

Women 27.3 (26.4, 28.3) 27.5 (25.9, 29.20)

BP >140/90mmHg, or on BP Drugs (%)

Men 58.0 (57.1, 58.9) 34.6 (31.7, 37.5)*

Women 55.2 (54.1, 56.2) 30.4 (27.7, 33.1)*(%) of these on treatment

Men 77.5 (77.8, 79.8) 41.9 (42.5, 52.9)*

Women 80.3 (84.8, 84.8) 53.0 (47.7, 58.3)*(%) BP controlled

Men 44.1 (42.6, 45.1) 24.0 (19.6, 28.4)*

Women 45.4 (45.4, 45.4) 27.0 (22.3, 31.7)*Cholesterol ≥5mmol/l (%) ( 16-64 years)

Men 29.4 (28.5, 30.3) 53.6 (49.8, 57.4)*

  Women 37∙2 (36.1, 38.3) 57.4 (53.7, 61.1)*HbA1c ≥6.5% (%) Men 93.1 (92.6, 93.6)

Women 94.0 (93.6, 94.6)* p<0.001 for difference between T1DM and general population

ObesityObesity, as defined by a BMI≥30, varies when examined by age group. Obesity rates are slightly higher in those with than without T1DM< 55 years of age and are then lower thereafter. Overall, obesity is less common in the men with T1DM than women, and less common in the population with T1DM than the general population; a relationship which is clearer with age standardisation for men (22.4% vs. 26.9%, p<0.001), but non-significant in women (27.3% vs. 27.6%, p=0.889).

Blood pressureBlood pressure control changes markedly across age ranges (Figure 1). Hypertension is more frequent in T1DM than the general population in every age group. In T1DM, but not in the general population, significantly more men than women have hypertension. Age standardised rates for hypertension show that treatment rates of hypertension are higher in T1DM than the general population (77.5% vs. 41.9% of those with BP >140/90mmHg or on antihypertensive medication; 80.3% vs. 53.0% in women, p<0.001).

Successful treatment, defined by a blood pressure <140/90mmHg, is nearly equal across the sexes in T1DM (44.1% for men, 45.4% for women), which is not the case for the general population (24.0% for men, 27.0% for women, p<0.001 for both sexes).

CholesterolCrude cholesterol levels are lower in T1DM than the general population (30.5% men ≥5mmol/l vs. 53.6% in the general population; 37.8% vs. 57.4% for women). Adjusted rates remain significantly different, at 29.4% for men and 37.2% for women (p<0.001 for both sexes). The difference between men and women with T1DM is also significant, indicating lower treatment rates in women.

MethodsThe Scottish Care Information–Diabetes Collaboration (SCI-DC) database was used to identify 21,290 people with T1DM aged ≥16 years who were alive any time from 1st Jan 2005 to 31st May 2008 with available risk factor data. We extracted risk factors (non-fasting lipids, blood pressure, current smoking, body mass index) and medication history. Comparable risk factor data was extracted from the SHS (n=7,531).

ConclusionsNearly twenty years ago, the Diabetes Care and Complications Trial (DCCT) demonstrated the preventability of many diabetic complications with tight glycaemic control7 and longer term follow up of the participants showed a reduction in CVD8. Since then guidelines have emphasised tighter glycaemic control, smoking cessation, blood pressure control, and above 40 years of age, statins are recommended for most patients9,10. To an extent these guidelines are having an effect: cholesterol levels are now substantially lower in type 1 diabetes patients than in the background population. This reflects the targeted use of cholesterol-lowering medication in this group. HbA1c levels however remain very high in those with diabetes. Hypertension and prevailing blood pressures remain higher despite more intensive intervention.

There remains substantial scope for much greater prevention of diabetic complications including an assertive attempt at preventing smoking uptake in those with T1DM. The gender

Glycaemic controlGlycaemic control, measured by HbA1c is broadly similar across age groups, as indicated by the fact that age standardisation has little effect (93.5% crude rate, 93.1% age standardised in men; 94.1% crude rate in women, 94.0% age standardised in women, p<0.001 for both sexes).

Figure 1. Blood pressure control in T1DM and general population, by age group

ResultsRates for the general population and age-standardised rates for the population with T1DM are shown by gender in Table 1.

SmokingCrude estimates of smoking prevalence show higher rates of smoking among men than women, and higher rates in men with T1DM than men the general population (29.1% vs. 26.0%), but this is non-significant after age standardisation, reduced to 27.5% (p=0.581). In contrast, women with T1DM have a lower smoking prevalence than the generalpopulation (23.9% vs. 25.0%), which is even lower after age standardisation (22.3%, p<0.001).

imbalance seen in some risk factors also merits urgent attention. In particular, the higher prevalence of smoking and hypertension in men, and the lower treatment rates for cholesterol in women. This latter may go some way to explaining the increased CVD risk seen in women with T1DM.

Comparisons were made within age bands and by sex. Prevalences and means in the T1DM population have been standardised against the age/sex distribution of the general population using the weighted denominators in the Scottish Health Survey6.