more_vert
GPs have an important role to play in raising awareness about the lifetime cumulative effect of lipid-carrying lipoproteins on the risk of cardiovascular disease, and helping patients redefine a “normal” diet as one that is heart-healthy.
Over the past decade, we have seen a shift in focus of lipid management from the “break-fix” model to a “predict-prevent” model. The predict-prevent approach focuses on the causal effect of low-density lipoprotein (LDL) and apolipoprotein B (apoB) on the risk of cardiovascular disease, determined by both the magnitude and the cumulative duration of exposure to these lipoproteins.
Cardiovascular disease risk increases with an individual’s cumulative exposure to LDLs, specifically LDL-cholesterol (LDL-C) and apoB, and earlier exposure can lead to an increased risk of developing clinical cardiovascular events later in life.
Key to maintaining optimal lipid levels throughout life is to keep the concentration of circulating LDL and other apoB-containing lipoproteins low. This helps to minimise the number of particles that become retained in the arterial wall, which reduces the rate of atherosclerotic plaques progression.
The potential clinical effectiveness of this strategy is supported by the observation that isolated populations that maintain lifetime exposure to low plasma levels of LDL have low lifetime risk of cardiovascular disease. For example, members of the Tsimane, a Bolivian population living a subsistence lifestyle, have a low mean LDL-C level of 2.35 mmol/L and a very low prevalence of coronary atherosclerosis as measured by coronary artery calcium (CAC) scoring, compared with populations with higher mean LDL-C levels (here and here).
Tsimane CAC scores are low, even at age 75 years and above. Studies demonstrated that 65% have no CAC and only 8.3% have a score over 100. Based on CAC scores and biomarkers, the arterial age of Tsimane is 28 years younger than matched industrial populations. The hunting and foraging diet of the Tsimane people shares many similarities with the popular Mediterranean diet – predominantly plant-based, with meat and fish in moderation – coupled with around 6 hours of daily exercise and minimal smoking.
Another level of evidence in support of lifelong lower LDL-C levels comes from recent intravascular studies of lipid-lowering therapies suggesting that the progression of atherosclerosis stops when plasma LDL-C is reduced to less than approximately 1.8 mmol/L.
Besides low LDL-C levels, other factors contributing to avoiding atherosclerosis during one’s lifetime include low blood pressure, normal fasting blood glucose, normal body mass index, a lifetime of no smoking, and plenty of physical activity.
One of the significant contributors to the build-up of atherosclerosis is poor dietary choices. The Primary Prevention of Cardiovascular Disease Mediterranean Diet trial evaluated the role of diet among persons at high cardiovascular risk. In both the original and republished study, the incidence of cardiovascular disease in the Mediterranean diet groups was lowered by approximately 30% when compared with the control diet. The incidence of major cardiovascular events was lower among those assigned to a Mediterranean diet supplemented with extra-virgin olive oil or nuts than those assigned to a reduced-fat diet.
Clinical data support the adoption of a heart-healthy diet, specifically the Mediterranean diet supplemented with olive oil, in reducing the burden of coronary artery disease. The Mediterranean diet has been shown to increase high density lipoprotein (HDL), decrease triglycerides, lower blood pressure, and reduce blood glucose levels.
Key components of the Mediterranean diet include high monounsaturated to saturated fat ratio (unrestricted use of olive oil as an ingredient in cooking and at the table) and/or consumption of traditional foods high in monounsaturated fats (tree nuts), high intake of plant-based foods (fruits, vegetables, legumes), low to moderate red wine consumption, high consumption of whole grains and cereals, low consumption of meat and meat products, increased consumption of fish, and moderate consumption of milk and dairy products.
The OmniHeart study showed a diet that partially replaced carbohydrate with protein, primarily from plant sources or with unsaturated, predominantly monounsaturated fat, had beneficial effects on blood lipids, reducing LDL-C and triglycerides and lowering blood pressure.
Dean Ornish, in his Lifestyle Heart trial, demonstrated that a whole food vegetarian diet, with aerobic exercise training and group psychosocial support, was associated with reduced atherosclerosis progression.
Lifestyle patterns begin from a young age, allowing redefining the new normal. With a focus on the “predict-prevent” model, we can start thinking about primordial prevention (preventing the development of risk factors) between the ages of 0 and 20 years, and an ongoing focus on primary prevention between the ages of 20 and 60 years.
There are emerging data regarding the detection of low CAC burden in younger adults and CAC scoring should be considered in younger patients with multiple risk factors. The detection of CAC at an earlier age offers further decades to prevent clinically significant atherosclerosis. For men, this may mean considering testing in the fourth decade.
Findings from the ongoing CARDIA study (Coronary Artery Risk Development in Young Adults) have shown that the higher availability of convenience and fast food outlets have led to the earlier development of CAC in young adults living in these areas.
As clinicians, we can assist our patients down the early prevention path, through awareness and education about the impact of lipids on plaque build-up, and the importance of heart-healthy dietary patterns.
In younger patients, the use of lifetime risk calculators are often more clinically useful and effective in motivating behavioural change compared with the majority of risk score calculators.
GPs have a critical role in managing the burden of heart disease in Australia, in both the management of current patients and in the prevention of future patients through an early heart-health intervention. It is never too early for patients to consider making these heart healthy lifestyle choices, but it is also never too late.
Dr Jason Kaplan is a GenesisCare cardiologist with a special clinical interest in cardiac imaging, cardio-oncology, preventive cardiology, sports cardiology, lifestyle, and dietary management of cardiovascular disease. Dr Kaplan is currently a senior clinical lecturer in Medicine in the Faculty of Medicine and Health Sciences at Macquarie University.
The statements or opinions expressed in this article reflect the views of the authors and do not represent the official policy of the AMA, the MJA or InSight+ unless so stated.