IJCRR

IJCRR - 5(6), March, 2013

Pages: 104-113

Date of Publication: 30-Mar-2013

EFFECT OF GENDER, AGE AND DURATION ON DYSLIPIDEMIA IN TYPE 2 DIABETES MELLITUS

Author: Shabana S., Sasisekhar T.V.D.

Category: Healthcare

Abstract:Introduction: The burden of dyslipidemia is high in patients with diabetes. Although there is considerable evidence that abnormalities in serum lipids and lipid metabolism are important risk factors for increased incidence of coronary artery disease in type 2 diabetes, controversy exists regarding the association of dyslipidemia with the gender, age and duration of diabetes. Objective: To study the prevalence and association of lipid disorders with gender, age, and duration of type 2 diabetes mellitus. Materials and methods: This is a cross-sectional prospective study of 270 diabetic patients at a tertiary care teaching hospital. The subjects were grouped based on the gender, age and duration of diabetes and into subgroups by a five year scale based on the age and duration of diabetes. Fasting venous blood samples were analyzed for serum total cholesterol (TC), triglycerides (TG), low-density lipoprotein LDL-C and high-density lipoprotein cholesterol (HDL-C). Results: Prevalence of dyslipidemia was more in female than in male diabetics. There was a gender preference of some lipid parameters. By age and by duration of diabetes, certain subgroups showed higher prevalence of dyslipidemia in both sexes. The degree of dyslipidemia by age showed an increasing trend and then reached a plateau, while it increased with increased duration of diabetes in both male and female diabetics. Although the distribution of lipid abnormalities increased with duration of diabetes, by age it showed no particular pattern of predominance in both sexes p>0.05. Conclusion: The predominance of dyslipidemia at an older age, the increased prevalence and higher lipid abnormalities in the female diabetics indicate that female diabetics are at a higher risk of atherosclerosis and subsequently coronary artery disease compared to male diabetics.

Keywords: Dyslipidemia, type 2 diabetes mellitus, atherosclerosis, coronary artery disease

Full Text:

INTRODUCTION

Diabetes is metabolically heterogeneous and dyslipidemia is commonly seen in diabetic patients. Lipid abnormalities in patients with diabetes play an important role in the development of atherogenesis. Together with hypertension and smoking, dyslipidaemia is an established risk factor for coronary artery disease (CAD), both in diabetic and non-diabetic patients. Patients with type 2 diabetes commonly have a number of risk factors for atherosclerosis, among which dyslipidaemia plays a major role in the excess CAD mortality associated with the condition [1]. Mortality from CAD is approximately three times higher in diabetic patients than in the general population [2]. The burden of dyslipidemia is high in patients with diabetes. These lipid disorders include not only quantitative but also qualitative abnormalities of lipoproteins which are potentially atherogenic [3]. Type 2 DM is associated with a cluster of interrelated plasma lipid and lipoprotein (LP) abnormalities that are all recognized as predictors for coronary heart disease [4]. Hypertriglyceridemia combined with a reduced HDL cholesterol is the most common dyslipidemia in patients with noninsulindependent diabetes mellitus, but essentially any pattern of dyslipidemia may be present [5]. Although there is considerable evidence that abnormalities in serum lipids and lipid metabolism are important risk factors for this increased incidence of CAD in type 2 diabetes, controversy exists regarding the association of dyslipidemia with the gender, age and duration of diabetes and reports of prevalence and distribution of dyslipidemia are varied. In view of the predisposition for the development of atherosclerotic vascular disease in the diabetics, attention has been focused on lipid and lipoprotein metabolism in diabetes. We aimed to investigate the prevalence and pattern of lipid disorders among type 2 diabetic patients. In particular, we investigated the prevalence and association of lipid disorders with gender, age, and duration of type 2 diabetes.

MATERIALS AND METHODS

This is a cross-sectional prospective study. A total of 270 patients of both sexes were randomly selected from the outpatient department of medicine, in Dr Pinnamaneni Siddhartha Institute of Medical Sciences and Research Foundation, a tertiary care teaching hospital. The study was approved by the institutions ethical committee and informed consent was obtained from all the subjects enrolled in the study. Subjects of both sexes, in the age group of 35-70 yrs who gave a history of diabetes and were under treatment with either oral antidiabetic drugs or insulin were included in the study. The subjects who gave a history of any cardiovascular, renal or thyroid disorders and whose duration of diabetes was less than 1 year or more than 15 years were excluded from the study. Patients on drugs known to affect lipids i.e., lipid lowering drugs, contraceptive pills, hormone replacement therapy, β-blockers, and thiazide diuretics were excluded from the study. The subjects were grouped based on the gender, age and duration of diabetes and into subgroups by a five year scale based on the age and duration of diabetes. Venous blood samples from all the subjects were collected after at least 8h fasting and analyzed for serum total cholesterol (TC), triglycerides (TG) and high-density lipoprotein cholesterol (HDL-C) on Randox (Daytona) autoanalyzer. Serum total cholesterol and triglycerides assay were done using enzymatic methods and HDL cholesterol by precipitation technique. The level of lowdensity lipoprotein cholesterol (LDL-C) was determined using the Friedwalds formula: LDL= Total Cholesterol – (TG/5 + HDL) when the values of TG were less than 400 mg%. For serum lipid reference level, National Cholesterol Education Programme (NCEP) Adult Treatment Panel III (ATP III) guideline was referred [6]. According to NCEP-ATPIII guideline, hypercholesterolemia is defined as TC >200 mg/dl, high LDL-C when value is >100 mg/dl, hypertriglyceridemia as TG >150 mg/dl and low HDL-C when value is <40 mg/dl. Dyslipidemia was defined by presence of one or more than one abnormal serum lipid concentration. Statistical analysis was carried out using Graph Pad Prism 6.0 version. Data were described as mean with S.D. for continuous variables and proportions for categorical variables. Anova test was used to assess statistical significance of the difference between continuous variables. Chi square test was used to assess statistical significance of the difference between categorical variables. A p value <0.05 was considered statistically significant. Bar diagrams were used to show the prevalence of dyslipidemia.

RESULTS

The study includes 130 male and 140 female subjects. The mean age in years of the male diabetics 54.53±10.23 was slightly lower than the mean age 55.27±9 of the female diabetics, and the duration of diabetes longer in the female than male diabetic subjects, 5.9±3.67 and 5.35±3.34 respectively. Serum total cholesterol and LDL cholesterol were slightly elevated in female diabetics and triglycerides in male diabetics but there was no statistical difference between the two groups. HDL cholesterol did not vary between the two genders [Table I]. Lipid variables were categorized by a 5 year age scale in the male and female diabetics. Among the various subgroups the mean serum total cholesterol, triglycerides and LDL cholesterol levels were higher and HDL cholesterol levels lower in the age group of 46-50yrs in the male diabetics but statistical significance was noted only with serum triglycerides. Female diabetics in the age groups of 46-50yrs and 51-55yrs showed higher levels of mean serum total cholesterol, triglycerides and LDL cholesterol and lower levels of HDL cholesterol compared to other subgroups but no statistical difference was noted among the various subgroups [Table II]. The duration of diabetes categorized on a 5 year scale in both male and female diabetics is shown in [Table III]. Although a statistical significance was observed for elevation of mean serum total cholesterol in male diabetic subjects and a significant rise in mean serum total cholesterol and LDL cholesterol in female diabetics were noted, a linear increase in the levels of mean serum total cholesterol, triglycerides and LDL cholesterol levels and decrease in the levels of HDL cholesterol was seen with increased duration of diabetes in both sexes. Prevalence of dyslipidemia was calculated based on the presence of one or more than one abnormal serum lipid concentration according to NCEP ATPIII guidelines. Overall prevalence of dyslipidemia in type 2 diabetics was 74% (199 cases) and higher in female diabetics 78% (109 cases) against 69% (90 cases) in male diabetics [Fig 1]. Prevalence of dyslipidemia by age was found to be higher in the sub groups between 41- 50yrs in male and 46-55yrs in female diabetics, in comparison with other subgroups [Fig 2]. Prevalence of dyslipidemia by duration has shown that incidence is slightly higher in the subgroup with 5-10yrs duration of diabetes in both the genders [Fig 3]. Data was categorized by proportions based on the distribution of the type of lipid abnormality according to gender, age, and duration of diabetes. Genderwise the proportions of lipid abnormalities were higher in the female than male diabetics. The most frequent type of dyslipidemia found was hypertriglyceridemia 48% and 54% with decreased HDL-C 48% and 51% in male and female diabetics respectively [Table IV] but there was no statistical significance. Among the diabetics categorized by age there appeared to be no particular pattern of distribution of lipid abnormalities and no statistical significance were noted in the lipid parameters among various subgroups both in male and female diabetics [Table V]. Although not statistically significant an increase in the distribution of all the lipid abnormalities with an increase in duration of diabetes was noted in both genders [Table VI].

DISCUSSION

Diabetes in adults is associated with a high risk of vascular disease, two to six times greater in people with type 2 diabetes than those without diabetes and is the leading cause of morbidity and mortality in type 2 diabetes [7,8,11]. The life expectancy of people with diabetes is reduced by nearly eight years due to increased mortality. The Chennai Urban Population Study, a populationbased study in Chennai, in South India, showed a prevalence of CAD of 11%, which is 10 times more than what it was in 1970. In the same study, the prevalence of CAD among diabetic subjects was 21.4%, 25.3% in known diabetes and 13.1% in newly diagnosed diabetes [9,10]. The relative risk for cardiovascular disease due to type 2 diabetes mellitus was twice in men and three times in women compared to non-diabetic men and women [11]. More recent data have confirmed the significant correlation between CAD mortality and increasing plasma triglyceride concentrations [2]. Hypertriglyceridaemia can lead to the development of atherosclerosis by a number of mechanisms. One of these involves a change in HDL metabolism. Several studies which have shown an inverse relationship between HDL concentrations and the risk of coronary events have also shown an inverse relationship between triglyceride and HDL concentrations [1,3,12]. In a study by Ogbera et al [13] the prevalence of dyslipidemia was found to be more in female than in male diabetics. Our study showed similar findings with varying degrees of lipid abnormalities. Serum total cholesterol and LDL cholesterol were slightly elevated in female diabetics and triglycerides in male diabetics. This gender preference in lipid parameters was also noted in other studies [14]. In the gender distribution of lipid abnormalities by proportion the percentages of elevated TC , TG, LDL-C and reduced HDL-C, were higher in the female than male diabetics 62% vs 48%, 76% vs 64%, 51% vs 48% and 46% vs 42% respectively with the most prevalent dyslipidemia being high serum triglycerides with low HDL cholesterol in both genders as was also observed by another study [15]. An earlier study has shown a significant decrease in various lipid components including total cholesterol, triglycerides and LDL with advancing age. But this was shown in a 10 year age scale, with highest parameters being in the group <50yrs [14]. In our study the prevalence of dyslipidemia by age appeared to be higher in the subgroups between 41-50years in male and in between 46- 55yrs in female diabetics. In both male and female subjects, there was a trend to higher levels of all lipids except HDL-C with increasing age, which reached a plateau after the age of 50yrs in male and 55yrs in female diabetics as noted by another study [16]. The distribution of the all types of lipid abnormalities by age showed no particular pattern of predominance. This data was in agreement with other studies although the cut off levels differed slightly [13]. In relation to duration of diabetes in our study the prevalence of dyslipidemia was found to highest in the subgroup with 5-10yrs duration of diabetes in both genders. A national cross-sectional chart audit study [17] of 2473 Canadian patients with type 2 diabetes revealed that 55% of patients with a diagnosis of diabetes of 2 years had dyslipidemia. This proportion rose to 66% in patients with diabetes for 15 years. A linear increase in mean serum total cholesterol, triglycerides and LDL cholesterol and a decrease in HDL cholesterol with increase in duration of diabetes was noted in both the genders in our study, in contrast to another study by Otamere et al [18] which did not show any association of lipid levels with duration of diabetes. The distribution of all the types of lipid abnormalities increased with an increase in the duration of diabetes in our study and this increasing trend was also observed by another study [19]. In an analysis of diabetes duration and risk of major cardiovascular disease events and total mortality by Wannamethee et al [20], only those with diabetes for more than eight years had an increased risk of cardiovascular disease and death, compared with those who had diabetes less than two years. CAD risk in patients with diabetes escalates significantly with disease duration and approaches CAD risk equivalence only when disease duration is beyond eight years. The abnormalities in serum lipids in our study were greater in diabetic women than men. In one study female subjects with type 2 diabetes had relatively greater elevation of serum triglyceride and reduction in HDL-C than men compared with controls [21]. These findings were confirmed in the much larger baseline studies from UKPDS [16] in which the simultaneous presence of low HDL-C and high triglyceride was associated with a four-fold risk of CAD and a two-fold risk of all CAD events. If these two parameters were combined with high total cholesterol, there was a four-fold risk of CHD death and three-fold risk of all CAD events. The incidence of coronary artery disease is significantly higher in men than in women until menopause, after which the incidence of coronary disease is similar in both sexes. Most commonly, these gender differences have been explained by the hormonal milieu and, most specifically, by the actions of sex steroids on the lipid profile [22].

CONCLUSION

From the present study we conclude that female diabetics are prone to dyslipidemia at an higher age than male diabetics. The increased prevalence and higher abnormalities of lipids in the female diabetics indicate a higher risk of atherosclerosis and subsequently CAD compared to male diabetics. Therefore there is an urgent need for screening and therapeutic intervention for dyslipidemia in the diabetics which may help to decrease the morbidity and mortality from CAD. Conflict of Interest: Nil

ACKNOWLEDGEMENTS

Authors acknowledge the great help received from the scholars whose articles cited and included in references of this manuscript. The authors are also grateful to authors / editors / publishers of all those articles, journals and books from where the literature for this article has been reviewed and discussed. Authors are grateful to IJCRR editorial board members and IJCRR team of reviewers who have helped to bring quality to this manuscript.

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