Improvement of serum lipids concentration in a general population historical cohort. Why?

BACKGROUND: Knowledge about the harmful effects of high levels of low-density lipoprotein cholesterol (cLDL) in adults increased after the publication of various guidelines, leading to closer control and more treatment. We hypothesized that these health care changes would result in an overall improvement in the lipid profile of the population.

OBJECTIVE: To determine the evolution of the lipid profile in the population of Spain from the Diet and Risk of Cardiovascular Disease in Spain cohort.

METHODS: A comparison was made between the baseline population-based probabilistically sampled DRECE cohort (DRECE 1 study, 1992-1994, n=4787) and its 13 years later revisit (DRECE 3 study, 2005-2007). A cross-sectional comparison was made of the overall population of DRECE1 and DRECE3, including only individuals aged 20 to 60 years (inter-individual variations). For subjects participating in both DRECE1 and DRECE3 (n=1039), individual variations over time (intra-individual analyses) were examined.

RESULTS: In the overall population, the prevalence of lipid-lowering therapy increased from 3.8% in DRECE1 to 10.7% in DRECE3. Comparing the lipid profile of the population aged 20-60 years in DRECE1 with the same age group in DRECE3, an overall decrease is observed in total cholesterol from a mean of 203.31mg/dl (SD 43.51) in 1992-1994 to 196.31mg/dl (SD 38.53) in 2005-2007, and in cLDL from a mean of 125.78mg/dl (SD 38.53) to 121.37mg/dl (SD 34.22). The proportion of the population with total cholesterol >200mg/dl decreased from 51% in DRECE1 to 47% in DRECE3, although this difference did not reach statistical significance (p=0.077). As regards the intra-individual analyses, total cholesterol increased from DRECE1 to DRECE3 in men and women younger than 40 years at baseline, but decreased in those who were older. Index of individuality for total cholesterol, cLDL, cHDL and triglycerides ranged from 0.53 to 0.87.

CONCLUSIONS: The lipid profile of the Spanish population improved between 1992-1994 and 2005-2007. Within individuals, lipid concentrations, especially total cholesterol and cLDL have increased, although the trend is favorable in the middle-age group (40-59 years). These changes seem to be due to several causes, impacted by dietary and lifestyle factors, and also by a greater emphasis in lipid-lowering therapy in middle-aged people. Lipid parameters had a low index of individuality, which limits their usefulness as population reference values.