Fasting Time and Lipid Levels in a Community-Based Population
Some studies suggest that nonfasting lipid profiles change minimally in response to food intake, and may be superior to fasting levels in predicting adverse cardiovascular outcomes. What is the association between fasting times and lipid levels in the current study?
Cross-sectional examination of laboratory data, including fasting duration (in hours) and lipid results, was performed over a 6-month period in 2011 in a large community-based cohort in Calgary, Alberta, Canada, in which laboratory services (source population, 1.4 million persons) were provided by a common laboratory. The main outcome measures were mean levels of high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), total cholesterol, and triglycerides for fasting intervals from 1 hour to more than 16 hours. After differences in individual ages were controlled for, linear regression models were used to estimate the mean levels of cholesterol subclasses at different fasting times.
A total of 209,180 individuals (111,048 females and 98,132 males) with mean age 52.8 years, total cholesterol 183 mg/dl, HDL-C 55 mg/dl, triglycerides 128 mg/dl, and calculated LDL-C of 103 mg/dl were included in the study. The mean levels of total cholesterol and HDL-C differed little (about 2%) among individuals with various fasting times. The mean calculated LDL-C levels showed slightly greater variations of up to 10% among groups of patients with different fasting intervals, and the mean triglyceride levels showed variations of up to 20%.
Fasting times showed little association with lipid subclass levels in a community-based population, which suggests that fasting for routine lipid levels is largely unnecessary.
There are many reasons for obtaining lipids in the nonfasting state than the obvious patient convenience. In both healthy and coronary disease populations as well as on treatment studies, nonfasting non–HDL-C (total cholesterol – HDL-C) is a better predictor of risk and outcome than any of the individual lipids and the ratio of total to HDL-C. What about the use of the LDL-C for deciding who to treat and the target, as based on the guidelines? Again, the non–HDL-C is a better alternative, with the cut point being 30 mg higher than the LDL-C (e.g., if target LDL-C is <70 mg/dl, target non–HDL-C is <100 mg/dl). Fasting lipids may be preferable for the initial assessment in diabetics, when the metabolic syndrome is suspected, and when monitoring the effects of diet or drug intervention on triglycerides.
Keywords: Cholesterol, Lipids, Canada, Lipoproteins, Triglycerides, Fasting
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