Atherosclerosis and its clinical complication, cardiovascular disease (CVD), is one of the most important causes of death in developed and industrialized countries. Different parameters have been identified as risk factors for CVD, plasma lipid abnormalities being one of them.

The causal relationship between elevated plasma low density lipoproteins-cholesterol (LDL-C) levels and the risk of CVD is well established in diabetic and non-diabetic subjects.1 In the UK Prospective Diabetes Study (UKPDS23) the LDL-C concentration was the best predictor of myocardial infarction in diabetic subjects.2 The dyslipidemia of type 2 diabetes is characterized by low levels of high density lipoproteins-cholesterol (HDL-C), moderately raised triglycerides (TG) and the accumulation of cholesterol enriched remnant lipoprotein particles, while total and LDL-C concentrations generally reflect those of the background population.3,4 This type of dyslipidemia is a significant contributor to the elevated CVD risk observed in type 2 diabetes mellitus. Intervention studies with lipid-lowering agents have shown significant reductions in CVD morbidity and mortality in primary and secondary prevention in diabetic subjects.5 Thus, detection and control of dyslipidemia is of particular interest for preventive cardiovascular measures.6

The aim of this study was to assess the prevalence of dyslipidemia and its association with glucose metabolism in a representative sample of the adult population in Spain. In addition, we have evaluated what percentage of them was at guideline-recommended LDL-C goals.

Table 1 shows the characteristics of the 4776 subjects (42.7% men) studied. There were no significant differences for age or diabetes prevalence between genders. Dyslipidemia was diagnosed in 56.8% of subjects; 13.2% of subjects (n=638) were treated with lipid lowering drugs, mostly statins, and have been analyzed separately from the 4138 individuals untreated with lipid-lowering agents.

Lipid values in untreated subjects, according to age and gender, are shown in Table 2. Mean total plasma cholesterol, LDL-C, TG and non-HDL-C levels increased with age through middle age, reaching a peak at ages 50–59 years, and then decreasing in both genders. Men presented higher total cholesterol levels than women for ages 30–49 years but these levels were lower after age 50. A similar trend was found for LDL-C, TG, and non-HDL-C. On the contrary, at all ages men had lower levels of HDL-C compared to women, the values staying stable at all ages. The percentiles of lipid levels in untreated subjects, according to age and gender are shown online in Table 1.

We have evaluated the relationship between glucose metabolism status and lipid values in untreated subjects (Table 3), separating them in three groups: normal glucose tolerance (NGT), prediabetes and diabetes. The prevalence of glucose impairment increased with age, and TG and non-HDL-C levels rose according to IGR, while HDL-C values decreased. Pre-diabetic and diabetic individuals had significantly higher levels of TC, LDL-C, TG and non-HDL compared to non-diabetic subjects. Moreover, diabetics had significantly higher levels of TG than pre-diabetics, and significantly lower levels of HDL-C. The prevalence of dyslipidemia increased progressively with rising glucose levels.

Table 4 shows the prevalence of dyslipidemia in the total group (treated and untreated subjects), the awareness of dyslipidemia and the percentage of subjects treated with lipid-lowering drugs. Lipid abnormalities were found in 56.8% of Spanish adults: 23.3% with high LDL-C; 21.5% high TG; 35.8% high non-HDL-C, and 17.2% had low HDL-C. The prevalence of dyslipidemia showed a tendency to rise with age, as well as the awareness and the percentage of subjects treated with lipid-lowering drugs. However, most of the subjects were unaware of the presence of dyslipidemia, and only a small proportion of those with known dyslipidemia were treated.

Fig. 1 shows the percentage of subjects in the total group reaching LDL-C goals according to their cardiovascular risk. Most of the NGT subjects achieved an LDL-C goal ≤3.36mmol/l. Prediabetics presented a similar proportion when considering a goal of 3.36mmol/l, but only 35% of them reached an LDL-C goal ≤2.6mmol/l. Finally, 45.3% of diabetics achieved an LDL-C ≤2.6mmol/l, but only 11.3% of them achieved an LDL-C goal ≤1.8mmol/l.

Figure 1.

Percentage of subjects in the total group (n=4776) reaching LDL-C goals according to their cardiovascular risk. Footnote: NGT n=3273; pre-diabetics n=1094; diabetics n=409.

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In a previous study, using a representative sample of the whole national population, the prevalence of diabetes mellitus in Spain was established at 13.8%, with 6.8% having undiagnosed diabetes that was discovered during the study.7 Diabetes is characterized by a clustering of cardiovascular risk factors. Of these, diabetic dyslipidaemia (increased levels of plasma triglycerides, low plasma levels of HDL-C, and elevated plasma levels of small dense LDL particles) is recognized as the most important modifiable risk factor for CVD in patients with diabetes.3,4 However, because of its asymptomatic nature the majority of individuals are unaware of it. Thus, early diagnosis and treatment of dyslipidemia is an important public health problem, particularly relevant in diabetic persons.

In the present study we have investigated the prevalence of lipid metabolism abnormalities detected in a sample representative of the adult population in Spain. Dyslipidemia was observed in 56.8% of the entire cohort, being more prevalent (66.6%) among men than in women (49.6%). Although both genders showed similar total cholesterol levels, men had higher LDL-C and TG levels, while women showed higher HDL-C. In both genders, total cholesterol and LDL-C levels increased with age, reaching a peak at ages 50–59 years. Men presented higher LDL-C levels than women up to 50 years, but their levels became lower than in women after 60 years of age. This finding could be ascribed, among other causes, to lower lipid levels in pre-menopausal females.10 Similar results were found for TG. On the contrary, HDL-C levels were higher in women at all ages. Our results are similar to that previously found by others in Spanish population.11 Moreover, although plasma lipid levels may vary in different cultures, our results are consistent with those found in other populations.10,12–14

Hyperglycemia and dyslipidemia are two of the most important risk factors for cardiovascular disease. Our study, in accordance with others15 showed that when untreated subjects were separated according to their glucose metabolism status, those with NGT showed the lowest prevalence (48.8%) of dyslipidemia, compared with the 69.5% found in prediabetes and the 87.3% found in diabetes. As expected, our study confirms the strong association of diabetes with elevated triglyceride levels, 49.1% of diabetic subjects had plasma TG levels ≥1.7mmol/L compared with 25.7% and 14.7% in the prediabetics and NGT groups, respectively. Moreover, the lipid profile in prediabetics included more abnormalities than in NGT subjects, as has been shown by other authors.15

Concerning LDL-C concentrations, the mean value in diabetic and prediabetic subjects was 2.8 and 2.9mmol/L, respectively, significantly higher than the 2.7mmol/L observed in NGT subjects. Although plasma LDL-C levels in IGR subjects are either normal or only modestly elevated, the LDL particle is smaller, carries less cholesterol and is denser. This profile of lipid abnormalities is referred to as diabetic dyslipidemia and contributes to the increased risk of atherosclerotic cardiovascular disease characteristic of type 2 diabetes.3,5 Our results are in accordance with those reported by Vinagre et al.16 in type 2 diabetes patients in Catalonia (Spain), with a mean LDL-C value of 2.9mmol/L, and the results of the DECODE Study15 which included subjects from 8 European communities.

With respect to HDL-C levels, plasma values are lower when glucose rises. Moreover, the prevalence of low-HDL-C was significantly higher in diabetics than prediabetics and NGT groups. However, there were no differences between the last two groups. A similar pattern was found in the DECODE study.15

We also evaluated the LDL-C goal attainment and the use of lipid-lowering drugs. Although epidemiological and interventional studies have shown a robust association between lipids and CVD, only 13.2% of subjects in our study were receiving treatment and only 33% of subjects were aware that they had dyslipidemia. These findings are similar to those reported in the 1999 to 2000 NHANES.17 Among treated subjects, statins were the lipid-lowering drugs most widely used (81.8%), with a therapeutic focus limited to LDL-C lowering. Lipid-lowering drugs prescriptions increased with age.

The percentage of subjects achieving LDL-C goals according to their cardiovascular risk varied according to the study groups. Most of the subjects with NGT, at low CVD risk, achieved an LDL-C goal ≤3.36mmol/l. However, in the two IGR groups, with higher CVD risk, the percentage of subjects who reached the LDL-C goal was lower. Although 73.7% of prediabetics attained an LDL-C goal ≤3.36mmol/l, only 35% of them achieved an LDL-C ≤2.6mmol/l. In spite of the elevated prevalence of dyslipidemia found in the diabetic group (87.3%) and the known high CVD risk in diabetics, only 32% of them were being treated with lipid-lowering agents. Consequently, the treatment targets were not reached in the majority of them. While 45.3% of diabetics reached an LDL-C ≤2.6mmol/l, only 11.3% were at the recommended ≤1.8mmol/l LDL-C goal. The degree of LDL-C goal achievement in diabetics was also low in other studies in Spanish population. In the DYSIS study, including individuals treated with statins at different doses, only 40.8% of diabetics achieved an LDL-C ≤2.6mmol/l.18 In the CODIMET study, diabetic individuals did not reach the recommended LDL-C target either. Only 37.6% presented an LDL-C ≤2.6mmol/l, and 13% achieved the LDL-C goal ≤1.8mmol/l.19

Although the di@bet.es study is a national, population-based survey, there are some limitations inherent to the design. It is a cross-sectional study and therefore it is not possible to evaluate factors affecting the prevalence and management of dyslipidemia. Moreover, the proportion of participants using lipid-lowering drugs could have been underestimated if participants failed to report their use. The proportion of subjects in secondary prevention was unknown. Thus the percentage of subjects achieving LDL-goals could be different. Finally, only the 55.8% attended examination.

Dyslipidemia is the most modifiable risk factor for atherosclerosis. Although diverse studies have shown that the prevalence of dyslipidemia has decreased in the last decades,12 our study demonstrates a high prevalence of dyslipidemia in the adult Spanish population, with a low use of lipid-lowering drugs. Moreover, the number of subjects achieving their corresponding LDL-C goal is small, particularly in subjects at high cardiovascular risk such as diabetics. Important efforts are necessary to implement control dyslipidemia and prevent CVD in our population.

The authors declare no conflict of interest.