Prevalence and pattern of dyslipidemia in patients with type 2 diabetes mellitus in Zaria, Northwestern Nigeria

Introduction Dyslipidemia confers excess atherosclerotic cardiovascular risk in type 2 diabetes mellitus (DM) patients, and this requires prompt identification and management to reduce morbidity and mortality. This study assessed the prevalence and pattern of dyslipidemia in type 2 DM patients in Zaria, Northwestern Nigeria. Methods This was a cross-sectional study of newly diagnosed type 2 DM patients at Ahmadu Bello University Teaching Hospital (ABUTH), Zaria. Demographic, clinical and laboratory data were extracted from the case notes of eligible patients and analyzed using STATA version 14. Continuous variables were presented as mean ± standard deviation (SD), or median and interquartile range (IQR) while categorical variables were as frequencies and percentages. Student t and chi-square tests were used to test for association at p < 0.05. Results A total of 322 subjects (161 male, 161 female) with a mean age of 53.5 ± 10.8 years partook in the study. The prevalence of dyslipidemia was 69.3%. Mixed dyslipidemia of high triglyceride (TG) and high low-density lipoprotein cholesterol (LDL-C) was present in 41.0%; high TG and low high-density lipoprotein cholesterol (HDL-C) in 2.8%; and high LDL and low HDL in 2.5%. Atherogenic dyslipidemia, isolated hypercholesterolemia and isolated low HDL-cholesterol were present in 3.4%, 2.5% and 23.6% respectively. Dyslipidemia status was not associated with age, sex, duration of DM or hypertension, obesity, and mean fasting blood sugar (FBS) and 2-hour postprandial glucose. Conclusion The prevalence of dyslipidemia is high in the newly diagnosed type 2 DM patients and therefore, initial management should incorporate measures to control dyslipidemia.


Introduction
Atherosclerotic cardiovascular diseases (ASCVD) defined as coronary heart disease, cerebrovascular disease, or peripheral arterial disease presumed to be of atherosclerotic origin represents the largest proportion of cardiovascular diseases (CVD), and is a leading cause of premature mortality and disability-adjusted life years (DALYs) globally [1][2][3]. In 2015, cardiovascular diseases were responsible for 31% (17.92 million) of the global annual deaths; out of which coronary heart disease (CHD) and cerebrovascular disease (stroke) claimed 7.4 million and 6.7 million lives respectively; and more than 75% of these occur in low-and middle-income countries [4,5]. Of the several risk factors attributed to the rising prevalence of atherosclerotic cardiovascular diseases, diabetes mellitus (DM) and dyslipidemia stand out as the most preventable and modifiable [6][7][8].
Nevertheless, rapid urbanization accompanied with changing lifestyle and demographics have led to a surge in the global prevalence of these twin diseases. In 2017, DM affected 425 million people aged 20-79 years globally, and this is projected to reach 629 million by 2045; 90% of this will be type 2 DM, and 79% will be from low-and middle-income countries [9]. Also, in 2008, raised cholesterol level ≥ 5.0 mmol/L occurred in 39% of the global adult population, 22.6% of this occurs in the African sub-region [10]. DM and dyslipidemia are intricately related and their co-existence helps to perpetuate ASCVD.
DM confers at least two to threefold excess risk, independent of other risk factors for ASCVD [11][12][13]; and patients with DM have poorer prognosis after cardiovascular events compared to non-diabetic patients [14]. On the other hand, the risk of CVD is greater at any level of serum cholesterol in patients with diabetes [15], and several studies have shown that cholesterol lowering therapies reduce the incidence of cardiovascular diseases in both diabetic and non-diabetic patients [16][17][18]

Results
A total of 322 patients (161 male and 161 female) with type 2 DM fulfilled the eligibility criteria and were included in the study. Their mean age was 53.5 ± 10.8 years while their mean body mass index and mean waist circumference were 27.8 ± 6.4 kg/m 2 and 92.8 ± 13.1 cm respectively. The mean fasting blood sugar and mean 2-hour postprandial sugar were 7.9 ± 3.1 mmol/L and 10.7 ± 3.5 mmol/L respectively, and 227 (70.5%) of them were hypertensive. Other clinical characteristic such as mean fasting blood sugar, mean 2h postprandial blood sugar, median duration of diabetic mellitus, median duration of hypertension, and mean serum lipid levels of the patients are as shown in Table 1. The prevalence of dyslipidemia in the patients was 69.3%. There was no significant difference in the prevalence of dyslipidemia between the female and male sexes, 68.3% vs. 70.2%, p = 0.717 (difference in proportion = -0.02, 95% CI = -0.12 to -0.08). The prevalence of atherogenic dyslipidemia, isolated hypercholesterolemia, isolated low HDL-cholesterol were 3.4%, 2.5%, and 23.6% respectively. Isolated hypertriglyceridemia and isolated high LDL cholesterol were not seen in these patients.
The prevalence of mixed dyslipidemias were: high TG and low HDL (2.8%), high TG and high LDL (41.0%) and high LDL and low HDL (2.5%). There were no statistically significant differences in the prevalence of the various dyslipidemia between the sex groups ( Table   2). Table 3 shows dyslipidemia status by demographic and clinical characteristics of the subjects. There were no statistically significant differences in the trend of dyslipidemia across age groups, duration of DM, duration of hypertension and grade of obesity. There were also no statistically significant differences in the proportion of males, hypertensives, truncal obesity, target mean FBS and target mean 2h postprandial sugar between subjects who had dyslipidemia and those with normolipemia.

Discussion
Diabetic dyslipidemia confers at least two-to-threefold excess risk for and patients with co-occurrence of high TG and low HDL are at increased risk of major coronary events [50,51]. The prevalence and pattern of dyslipidemia in the patients were not affected by sex, age, duration of diabetes, hypertensive state, duration of hypertension, body mass index, truncal obesity and mean FBS and 2hPP glucose.
Though these findings are in agreement with findings from Omotoye et al. [40] and Sang et al. [37]; findings from the UKPDS [30], Goel et al. [52], and Pokharel et al. [38] show varying association of dyslipidemia with some sociodemographic and clinical parameters of type 2 DM patients.

Conclusion
The study highlights the high prevalence of dyslipidemia in patients with type 2 diabetes mellitus attending clinic at ABUTH, Zaria, Nigeria

Competing interests
The authors declare no competing interests.

Authors' contributions
Beatrice  Tables   Table 1: demographic and clinical characteristics of patients studied