This prospective observational study investigated the clinical significance of fasting and non-fasting lipid profiles in Chinese CHD patients. All the participants had luminal stenosis > 40% in the main branches of coronary arteries and most of them had received statins for at least three months before enrollment. We found that CHD patients with either intermediate (40%-70%) or severe stenosis (> 70%) had an apparent change from the fasting state to four hours after normal food intake in the levels of lipoproteins and apolipoproteins. Although the level of lipids altered in response to daily diet, both fasting and non-fasting levels of lipoproteins and apolipoproteins had similar predictive value for MACE in Chinese CHD patients, regardless of the severity of coronary artery stenosis, age, male, smoking or diabetes. LDL-C and Apo B in either fasting or non-fasting state had strong association with increased MACE risk in CHD (fasting: HR 1.592 and 6.538, non-fasting: HR 1.657 and 5.350; both p < 0.001). On the contrary, fasting and non-fasting levels of HDL-C and Apo A1 were negatively association with MACE risk (fasting: HR 0.248 and 0.199, non-fasting: HR 0.130 and 0.128; both p < 0.001). Even though fasting lipid measurement is currently recommended by the guidelines in China, our findings have suggested the feasibility of using non-fasting lipids for CHD management in routine clinical practice.
For many years, most societies, guidelines, and statements has recommended to measure lipid profiles in the fasting state for cardiovascular risk assessment. This may be due to the dynamic changes observed in some lipid components, especially triglyceride during a postprandial (high-fat tolerance) test. In fact, people eat much less fat in a normal daily life and they are also mostly in a non-fasting state within 24 hours a day. Thereafter, several large-scale, population-based studies including children, women, men, and diabetic patients compared the fasting and non-fasting levels of lipids in response to daily food intake [3–7]. They found a slight elevation in non-fasting TG (0.1-0.3mmol/L or 10–21% increase from fasting state) [3–7] and minor decline in non-fasting TC (0.1-0.3mmol/L or 1–8% reduction from fasting state) and LDL-C (0.1–0.3 mmol/L or 4–9% reduction from fasting state) [3, 4, 6, 7]. However, the alteration between fasting and non-fasting HDL-C levels remained inconsistent. Based on the Copenhagen General Population Study, the maximal mean change at 1–6 h after habitual meals was − 0.1mmol/L for HDL-C [3]. Some studies showed that non-fasting HDL-C level remained unchanged in children aged 12 years or older, or in the large community-based cohort [6, 7]. Taken together, these studies suggested that lipids and lipoproteins changed slightly in response to normal food intake in both men, women, and children.
The effect of daily food intake on plasma lipids has been fully evaluated in western-population based studies. However, the characteristics of non-fasting lipids in Chinese CHD population after traditional Chinese food intake has rarely been investigated. Previous studies showed that compared with fasting levels, overall levels of TC and LDL-C gradually decreased from 1 to 4 hours following normal food intake and TG level increased up to 6 hours after the last meal [3, 15]. Hence, the non-fasting blood samples for lipid measurement were collected 4 hours after a daily breakfast in the present. We found that CHD patients with either intermediate or severe stenosis had a significant reduction from fasting state in the levels of non-fasting TC, LDL-C, and non-HDL-C. An obvious increase in non-fasting levels of TG and RC was present only in CHD patients with intermediate stenosis whereas a significant reduction in non-fasting HDL-C was obtained in severe stenosis group but not in intermediate stenosis group. Overall, the pattern of difference between fasting and non-fasting lipoproteins in the present study are in line with previous large-scale cohort studies in Western populations [3–7]. The alterations of lipoproteins after food intake is possibly attributed to overproduction and decreased catabolism of triglyceride-rich lipoproteins and their remnants, especially in patients with hypertriglyceridemia, metabolism syndrome or diabetes [16, 17]. Transfer of triglycerides from triglyceride-rich lipoproteins to HDL and LDL particles in exchange for cholesteryl esters leads to reduced levels of HDL-C and LDL-C in non-fasting state [18].
Notably, the present study found significant changes in the levels of apolipoproteins from fasting to non-fasting state were observed in CHD patients with either intermediate or severe stenosis. However, the Danish general population study, the Copenhagen General Population Study and the Copenhagen City Heart Study have showed that Apo B, and Apo A1 do not change in response to normal food intake [3]. The discrepancy may be due to different study population and different dietary habit.
In order to explore the clinical significance of non-fasting lipid profiles in response to daily diet in Chinese CHD patients, the association of fasting or non-fasting lipid profiles with the stenosis severity of coronary artery was evaluated. In the univariable logistic regression model, both fasting and non-fasting TC, LDL-C, HDL-C and Apo A1 were significantly correlated the severity of coronary artery stenosis. By multivariate logistic regression analysis, fasting or non-fasting HDL-C and Apo A1 remained to be associated with the stenosis severity, in addition to the classical risk factors, including age, male, diabetes mellitus and prior CHD history.
Furthermore, the present study evaluated the significance of non-fasting lipoproteins and apolipoproteins in long-term MACE risk assessment in CHD patients. Both the fasting and non-fasting levels of lipoproteins (LDL-C and HDL-C) and apolipoproteins (Apo A1 and Apo B) were identified as independent predictors of 5-year MACE risk by multivariate Cox proportional hazards analysis, besides the conventional risk factors (age, male, diabetes and smoking) and the severity of coronary artery stenosis. Our findings are consistent with numerous large-scale, prospective studies with long-term follow-up. These previous studies have demonstrated that non-fasting lipid levels are equally solid as risk predictors for cardiovascular disease and mortality compared with fasting lipid profiles [3, 4, 8–10]. A meta-analysis from the Emerging Risk Factors Collaboration enrolled 68 long-term prospective studies, more than 300000 individuals, mostly in Europe and North America and analyzed the association of major lipids and apolipoproteins with the risk of vascular disease [11]. They found that the strength of the association between lipoproteins and CHD risk was not attenuated in the 20 studies using non-fasting lipid measurements. HR for vascular disease risk with lipid levels were at least as strong in non-fasting state as in fasting state [11].
In 2009, the Danish Society of Clinical Biochemistry firstly made an official recommendation on measuring lipids in the non-fasting state for cardiovascular risk prediction [12]. Subsequently, the American Heart Association (AHA) [19], National Institute for Health and Care Excellence (NICE) [13], the European Atherosclerosis Society and the European Federation of Clinical Chemistry [20], the Canadian Cardiovascular Society [21, 22] as well as other societies [23] have updated their guidelines or statement and recommended non-fasting lipid profiles for cardiovascular risk prediction. Additionally, some major statin trials, such as Heart Protection Study [24], Anglo-Scandinavian Cardiac Outcomes Trial [25], Study of the Effectiveness of Additional Reductions in Cholesterol and Homocysteine [26], used non-fasting blood sampling for lipid assessment. Although prospective studies have suggested the advantages and clinical significance of non-fasting lipids for cardiovascular risk prediction, there are lack of cost-effectiveness studies [27–29]. Driver et al. pointed that clinicians should take careful considerations of clinical scenarios (initial cardiovascular risk assessment, residual risk of CHD, diagnosis of familial hyperlipidemia or metabolic syndrome etc.) when choosing between fasting and non-fasting lipids [30].
In current China, the levels of lipids in fasting state are still routinely used in the cardiovascular risk assessment. Our study has provided preliminary evidence on the value of non-fasting lipoproteins and apolipoproteins in cardiovascular risk assessment in Chinese CHD patients. Meanwhile, Lin et al. suggested that the non-fasting LDL-C level could replace the fasting value to guide treatment in Chinese CHD patients when the fasting LDL-C level was < 1.4 mmol/L [15]. Taken together, more research in large-scale Chinese population is indispensable to evaluate the association between non-fasting lipid profiles and cardiovascular risk. If non-fasting lipid profiles are accepted to assess cardiovascular risk throughout the world, it would greatly simplify clinical care for both medical practitioner and patients.
This study has some limitations that should be acknowledged. Firstly, we investigated CHD patients with intermediate or severe stenosis, most of whom received statins therapy. Our findings cannot be applied to the newly diagnosed CHD population who have not received standard treatment. Secondly, the lipid profiles were not regularly monitored and the proportion of patients reaching the target LDL-C levels (< 1.4 mmol/L) was not carefully evaluated during the follow up. Thirdly, non-fasting lipid profiles are affected by food habit, but we did not examine the patients’ dietary intake, alcohol use or use of supplements in the study.