The relative importance of particle count, type, and size of ApoB-containing lipoproteins in risk of myocardial infarction

Background

An accumulating body of evidence suggests that the number of apolipoprotein B-containing particles (ApoB-P) is more predictive of cardiovascular risk than their lipid content. However, it is unclear if this association is consistent across different lipoprotein types and sizes.

Purpose

We aimed to evaluate if particle type and size are associated with incident myocardial infarction (MI) beyond ApoB-P count. Moreover, we aimed to determine if the risk associated with lipoprotein(a) is additive to that of ApoB-P.

Methods

This prospective cohort study included 96,126 participants without prior history of stroke, coronary or peripheral artery disease or use of lipid-lowering medication from the UK Biobank. Count and size of VLDL, IDL, LDL, and HDL, as well as ApoB level and total ApoB-P count were measured in non-fasting plasma samples by nuclear magnetic resonance platform. Lipoprotein(a) was measured by immunoturbidimetric assay. We explored associations between these lipoprotein markers and incident MI using Cox proportional hazard models adjusted sequentially for clinical covariates, HDL count and size, and ApoB-P.

Results

Over a median follow-up of 12.1 years, 1702 participants had incident MI. In unadjusted models, 1-SD increases in ApoB-P count, ratio of VLDL to (LDL+IDL) particle counts, VLDL size and lipoprotein(a) were associated with a higher risk of MI, while LDL size was associated with a lower risk of MI (Table 1). When adjusting for clinical covariates and lipid parameters, only ApoB-P and lipoprotein(a) remained significantly associated with a higher risk of MI (HR: 1.40 [1.32; 1.48] and 1.20 [1.14; 1.27], respectively). Adjusted restricted cubic splines confirmed findings from linear trend Cox models (Figure 1). ApoB-P count was highly correlated with ApoB level (r=0.99), and replication of analyses replacing one for another revealed no change in results.

Conclusion

The risk of MI is independently associated with the total particle count of all ApoB-P, and not the size or type of these lipoproteins. ApoB level can be used as a very accurate surrogate of ApoB-P count in the clinical setting. Lipoprotein(a) is associated with MI risk independently of total particle count, and therefore, the combination of ApoB and lipoprotein(a) may provide the optimal clinical evaluation of lipid-mediated MI risk.

Funding Acknowledgement

Type of funding sources: None.

Associations between saturated fatty acids from different dietary sources and cardiovascular disease risk in 114,285 UK Biobank study participants

Background

Previous studies suggest that different foods rich in saturated fatty acids (SFA), particularly meat and dairy, have diverging directions of association with risks of total cardiovascular disease (CVD) and CVD subtypes.(1,2)

Purpose

To investigate the associations between SFA from different dietary sources and risks of total CVD, ischaemic heart disease (IHD), and stroke.

Methods

We analysed data on 114,285 UK Biobank participants who had completed ≥2 24-h dietary assessments and were free of CVD at the date of the latest 24-h dietary assessment. Risks of incident (non-fatal and fatal) total CVD, IHD and stroke by intakes of SFA from different sources were estimated using multivariable Cox regressions. Additional models assessed the role of body mass index (BMI) and low-density lipoprotein cholesterol (LDL-C) as potential mediators. We also estimated the associations between modelled isoenergetic substitution of 5% energy from SFA from meat with SFA from dairy, polyunsaturated fatty acids, monounsaturated fatty acids, carbohydrates from whole grains and carbohydrates from fruit and vegetables, and risk of CVD outcomes. A false discovery rate controlling procedure was used to account for multiple testing.

Results

Over a median 8.5 years of follow-up, there were 4,365, 3,394, and 1,041 cases of total CVD, IHD and stroke, respectively. There were no significant associations between total SFA intake and CVD outcomes. SFA from meat was positively associated with total CVD (hazard ratio for each 5% of energy, 1.19; 95% CI, 1.05–1.35) and IHD (1.21; 1.05–1.39) risk independently of lifestyle and cardiovascular risk factors. However, the estimates were attenuated and non-significant for both total CVD (1.11; 0.98–1.26) and IHD (1.12; 0.97–1.29) after adjustment for BMI. SFA from dairy was inversely associated with IHD risk (0.89; 0.82–0.96) in the multivariable model, however this finding was also attenuated after adjustment for BMI and did not pass correction for multiple testing (0.91; 0.84 to 0.98). Modelled replacement of 5% of energy from SFA from meat with carbohydrates from whole grains or carbohydrates from fruit and vegetables were associated with lower risk of stroke in the multivariable model (0.86; 0.78–0.94 & 0.86; 0.78–0.95, respectively) and the model adjusted for BMI and LDL-C (0.87; 0.79–0.96 & 0.86; 0.78–0.95, respectively).

Conclusion(s)

SFA from meat was associated with a higher risk of total CVD and IHD, while SFA from dairy was associated with lower risk of IHD, although BMI seemed to account for a large proportion of these associations. It is possible that diverging associations of SFA from different sources with CVD risk may explain the overall null association with total SFA observed in this study and some previous observational studies. Randomised controlled trials are needed to confirm whether replacing SFA from meat by carbohydrate from wholegrains or fruit and vegetables may be beneficial in reducing stroke risk.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Clarendon Fund and Jesus College Clarendon Old Members' AwardJesus College Graduate Scholarship

Sex-specific relevance of diabetes to occlusive vascular and other mortality: a collaborative meta-analysis of individual data from 980 793 adults from 68 prospective studies

BACKGROUND

Several studies have shown that diabetes confers a higher relative risk of vascular mortality among women than among men, but whether this increased relative risk in women exists across age groups and within defined levels of other risk factors is uncertain. We aimed to determine whether differences in established risk factors, such as blood pressure, BMI, smoking, and cholesterol, explain the higher relative risks of vascular mortality among women than among men.

METHODS

In our meta-analysis, we obtained individual participant-level data from studies included in the Prospective Studies Collaboration and the Asia Pacific Cohort Studies Collaboration that had obtained baseline information on age, sex, diabetes, total cholesterol, blood pressure, tobacco use, height, and weight. Data on causes of death were obtained from medical death certificates. We used Cox regression models to assess the relevance of diabetes (any type) to occlusive vascular mortality (ischaemic heart disease, ischaemic stroke, or other atherosclerotic deaths) by age, sex, and other major vascular risk factors, and to assess whether the associations of blood pressure, total cholesterol, and body-mass index (BMI) to occlusive vascular mortality are modified by diabetes.

RESULTS

Individual participant-level data were analysed from 980 793 adults. During 9·8 million person-years of follow-up, among participants aged between 35 and 89 years, 19 686 (25·6%) of 76 965 deaths were attributed to occlusive vascular disease. After controlling for major vascular risk factors, diabetes roughly doubled occlusive vascular mortality risk among men (death rate ratio [RR] 2·10, 95% CI 1·97-2·24) and tripled risk among women (3·00, 2·71-3·33; χ2 test for heterogeneity p<0·0001). For both sexes combined, the occlusive vascular death RRs were higher in younger individuals (aged 35-59 years: 2·60, 2·30-2·94) than in older individuals (aged 70-89 years: 2·01, 1·85-2·19; p=0·0001 for trend across age groups), and, across age groups, the death RRs were higher among women than among men. Therefore, women aged 35-59 years had the highest death RR across all age and sex groups (5·55, 4·15-7·44). However, since underlying confounder-adjusted occlusive vascular mortality rates at any age were higher in men than in women, the adjusted absolute excess occlusive vascular mortality associated with diabetes was similar for men and women. At ages 35-59 years, the excess absolute risk was 0·05% (95% CI 0·03-0·07) per year in women compared with 0·08% (0·05-0·10) per year in men; the corresponding excess at ages 70-89 years was 1·08% (0·84-1·32) per year in women and 0·91% (0·77-1·05) per year in men. Total cholesterol, blood pressure, and BMI each showed continuous log-linear associations with occlusive vascular mortality that were similar among individuals with and without diabetes across both sexes.

INTERPRETATION

Independent of other major vascular risk factors, diabetes substantially increased vascular risk in both men and women. Lifestyle changes to reduce smoking and obesity and use of cost-effective drugs that target major vascular risks (eg, statins and antihypertensive drugs) are important in both men and women with diabetes, but might not reduce the relative excess risk of occlusive vascular disease in women with diabetes, which remains unexplained.

FUNDING

UK Medical Research Council, British Heart Foundation, Cancer Research UK, European Union BIOMED programme, and National Institute on Aging (US National Institutes of Health).