Mednotes

L6 Public Health Heart health for New Zealanders

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aliasesL6 Public Health Heart health for New Zealanders

15 min read

Overview

This lecture covers population-level and lifestyle approaches to preventing cardiovascular disease (CVD) in New Zealand: the role of the Heart Foundation, the cardiovascular risk assessment framework used to guide treatment decisions, dietary patterns and their trial evidence (heart-healthy diet, DASH, Mediterranean diet, saturated fat reduction), WHO global NCD targets, the salt/sodium-blood pressure-CVD pathway and policy responses to it, and the evidence around alcohol and CVD risk. The parts fit together as a “population approach” to prevention: national guidelines and food/salt policy operate alongside individual dietary and lifestyle advice, with risk assessment used to decide when drug therapy is added.

Prevention approaches to CVD

  • Three approaches to ‘prevention’ of CVD: Population Approach, High Risk Approach, and Treatment.

The Heart Foundation

  • Founded 1968, a charitable organisation supported by the Ministry of Health and donations.
  • Provides guidance on prevention, treatment, rehabilitation and research.
  • Stated purpose: to stop all people in New Zealand dying prematurely from heart disease and to enable people with heart disease to live full lives.
  • Key statistics: 175,000 people living with heart disease in NZ; almost 1 in 3 deaths in NZ are caused by cardiovascular disease; every 90 minutes a New Zealander dies from heart disease, many premature and preventable; $90m invested into research since 1968.
  • Works with health professionals to share evidence-based guidelines, materials and resources, and runs professional development courses; publishes position and policy statements.
  • Runs public campaigns linking pulse-checking to identity/whakapapa (“Know Your Pulse. Know Your Whakapapa”).

Cardiovascular risk assessment and shared treatment decisions

Recommended interventions, goals and follow-up by CVD risk category (Table 5):

  • Established CVD: lifestyle advice (diet, weight management, physical activity, smoking cessation) for all categories. Strong evidence supports pharmacotherapy for modifiable risk factors and antiplatelet therapy for secondary prevention. Review annually.

  • 15% CVD risk: strong evidence supports statins and blood pressure lowering to prevent CVD events and death. Review annually; repeat risk assessment annually.

  • 5-15% CVD risk: discuss the magnitude of benefit of statins and blood pressure lowering with the patient (higher risk means more likely to benefit). Repeat risk assessment at 5 years for 5-9% risk, at 2 years for 10-14% risk.
  • <5% CVD risk: medication management has limited benefit. Repeat risk assessment at 10 years for <3% risk, at 5 years for 3-5% risk.
  • People with diabetes: recommend annual review regardless of risk category.
  • Lifestyle advice is emphasised as applying across every risk category.

Diet and cardiovascular health

  • Diet is a major contributor to CVD mortality globally: diets high in sodium and low in whole grains show the highest attributable mortality rates, and cardiovascular disease is the dominant cause of death across nearly all dietary risk categories (GBD 2017 Diet Collaborators).

Heart Foundation’s nine steps to eating for a healthy heart:

  1. Enjoy three meals a day, selecting dishes that encourage plant foods and fish, with little or no dairy fat, meat fat or deep-fried foods.
  2. Choose fruits and/or vegetables at every meal and for most snacks.
  3. Select whole grains, whole-grain breads or high-fibre breakfast cereals in place of white bread and low-fibre varieties.
  4. Include fish, dried peas/beans/soy products, or a small serving of lean meat or skinned poultry, at one or two meals daily.
  5. Choose low-fat milk, low-fat milk products, soy or legume products every day.
  6. Use nuts, seeds, avocado, oils or margarine instead of animal and coconut fats.
  7. Drink plenty of fluids, particularly water; limit sugar-sweetened drinks and alcohol.
  8. Use only small amounts of sugar or salt when cooking; choose ready-prepared foods low in saturated fat, sugar and sodium.
  9. Mostly avoid or rarely include butter, deep-fried and fatty foods, and sweet bakery products/pastries.

2021 AHA scientific statement — evidence-based dietary guidance for cardiovascular health (food-based rather than nutrient-based, consistent with a range of dietary patterns/traditional diets/cultural practices):

  1. Adjust energy intake and expenditure to achieve and maintain a healthy body weight.
  2. Eat plenty of fruits and vegetables, a wide variety.
  3. Choose foods made mostly with whole grains rather than refined grains.
  4. Choose healthy protein sources: mostly plant protein (legumes, nuts); fish and seafood; low-fat/fat-free dairy instead of full-fat; lean cuts if meat/poultry is desired, avoid processed forms.
  5. Use liquid plant oils rather than tropical oils, animal fats, or partially hydrogenated fats.
  6. Choose minimally processed foods instead of ultra-processed foods.
  7. Minimise beverages and foods with added sugars.
  8. Choose and prepare foods with little or no salt.
  9. If you do not drink alcohol, do not start; if you drink, limit intake.
  10. Adhere to this guidance regardless of where food is prepared or consumed.

DASH diet:

  • Benefits: lowers blood pressure and LDL “bad” cholesterol.
  • Eat: vegetables, fruits, whole grains, fat-free/low-fat dairy, fish, poultry, beans, nuts and seeds, vegetable oils.
  • Limit: fatty meats, full-fat dairy, sugar-sweetened beverages, sweets, sodium.
  • Trial evidence (Sacks et al 2001): reducing sodium and following the DASH diet each independently lower systolic blood pressure, and combining both produces the largest reduction (e.g. High(Control)→High(DASH) mean difference −5.9 mmHg, 95% CI −8.0 to −3.7).

Mediterranean diet — PREDIMED trial (2018): 7447 participants (55-80 years, 57% women) at high cardiovascular risk but without CVD at enrolment, assigned to Mediterranean diet + extra-virgin olive oil (EVOO), Mediterranean diet + mixed nuts, or a control diet (advice to reduce dietary fat).

  • Mediterranean diet recommendations: olive oil ≥4 tbsp/day; tree nuts/peanuts ≥3 servings/wk; fresh fruits ≥3 servings/day; vegetables ≥2 servings/day; fish/seafood ≥3 servings/wk; legumes ≥3 servings/wk; sofrito ≥2 servings/wk; white meat instead of red meat; wine with meals (optional, habitual drinkers only) ≥7 glasses/wk. Discouraged: soda <1/day; commercial bakery/sweets/pastries <2/wk; spread fats <1/day; red/processed meats <1/day.
  • Outcome: primary end point was a composite of acute MI, stroke, and CVD death. Both Mediterranean diet groups had lower cumulative incidence than control over 5 years. Hazard ratios vs control: Med diet + EVOO HR 0.69 (95% CI 0.53-0.91); Med diet + nuts HR 0.72 (95% CI 0.54-0.95) — roughly a 30% relative reduction in the composite CVD event/death outcome with either Mediterranean diet intervention.

Saturated fat (SFA) reduction — Cochrane review (Hooper et al 2020):

  • Lower SFA vs higher SFA diets, combined cardiovascular events across 12 trials: pooled Risk Ratio 0.83 (95% CI 0.70-0.98) — about a 17% reduction in combined cardiovascular events with lower saturated fat intake.
  • Exploration of saturated fat cut-offs: at lower SFA cut-offs (7-9% of energy) relative risk of most outcomes (CVD events, MI, stroke) is markedly lower; as the cut-off rises toward 10-13% energy, relative risk rises toward or above 1.0 — i.e. reducing saturated fat to a lower percentage of energy intake is associated with greater cardiovascular risk reduction.

WHO global NCD targets

WHO Global Action Plan for the Prevention and Control of Noncommunicable Diseases 2013-2020 — voluntary global targets:

  • 25% relative reduction in risk of premature mortality from cardiovascular disease, cancer, diabetes or chronic respiratory disease.
  • At least 10% relative reduction in harmful use of alcohol.
  • 10% relative reduction in prevalence of insufficient physical activity.
  • 30% relative reduction in mean population intake of salt/sodium (highlighted for emphasis).
  • 30% relative reduction in prevalence of current tobacco use in persons aged 15+.
  • 25% relative reduction in prevalence of raised blood pressure, or contain its prevalence, according to national circumstances.

Salt/sodium, blood pressure and cardiovascular disease

  • Pathway: salt/sodium intake raises blood pressure, which raises risk of CHD/stroke; salt/sodium intake also has a direct pathway to CHD/stroke independent of blood pressure.
  • Evidence linking sodium intake to elevated blood pressure is consistent across multiple study types: animal studies, epidemiological studies, migration studies, population intervention studies, treatment trials, and systematic reviews/meta-analyses.
  • Meta-analysis of outcome trials of salt reduction (combining hypertensive and normotensive individuals, follow-up 7 months to 11.5 years): reduction in risk of CVD events with decreased sodium, RR 0.80 (95% CI 0.64-0.99), p=0.04.
  • WHO recommendations (2012): adults should consume <2000mg sodium per day (5g salt, around 1 teaspoon). Globally people consume on average 3.6-5g sodium (9-12g salt) per day — around twice the recommended maximum.

Salt reduction strategies:

  • Consumer awareness and education.
  • Improvements in food labelling (e.g. Health Star Rating, traffic-light labelling of fat/saturates/sugar/salt).
  • Reformulation of processed foods according to specific targets, using a “sinking lid” approach.
  • Salt substitutes (e.g. reduced-sodium salt products with substantially less sodium than regular salt).
  • WHO “SHAKE the salt habit” technical package for salt reduction.
  • Example of front-of-pack warning labelling as a policy tool: Chile’s mandatory black octagonal warning labels (“high in calories,” “high in saturated fats,” “high in sodium,” “high in sugars”) were associated with a 23% cut in sugary drink sales.
  • Media coverage of nutrition science has at times presented conflicting messaging over time (e.g. reversals of “fat is the enemy” framing and disputes over the strength of evidence for salt reduction).

Alcohol and cardiovascular disease

  • The relationship between alcohol and CVD is often described as a J-shaped curve: some protective association at low intake, rising risk at higher intake.
  • Ecological data (e.g. IHD mortality vs national wine consumption, The Lancet 1979) showing countries with higher wine consumption (France, Switzerland, Italy) clustering toward lower IHD mortality, and countries with lower wine consumption (Finland, USA, Scotland, NZ, Australia) clustering toward higher IHD mortality, gave rise to the “French paradox” and questions about whether red wine itself is protective or whether the association reflects confounding.
  • Dose-response modelling (pooled analysis of 51 studies including 28 higher-quality cohort studies): relative risk of CHD falls below 1.0 at low alcohol intake, reaching a nadir around 20 g/day, then rises back above 1.0 by around 72 g/day and continues rising by around 89 g/day and beyond.
  • Gender effect: women’s dose-response curve rises back above relative risk 1.0 at a lower level of alcohol intake than men’s curve, so women reach harmful risk levels at a lower alcohol intake than men, though both sexes show the same general J-shaped (protective-then-harmful) pattern.
  • Arguments for a genuine protective effect (biological plausibility): lipid effects (raised HDL cholesterol), platelet effects (aspirin-like) and effects on fibrinolysis, and effects on glucose metabolism (reduced diabetes risk); consistency across large, well-conducted cohort studies.
  • Reasons for caution: no randomised controlled trials exist; patterns of alcohol use are associated with other health-related behaviours; the possibility of confounding remains.
  • Current Heart Foundation position: no amount of alcohol is good for your heart; the Heart Foundation does not recommend drinking alcohol to improve heart health. Alcohol increases the risk of high blood pressure — every 10g increase in pure alcohol per day (about 1 standard drink) raises the risk of high blood pressure by 6%. Alcohol also increases risk of atrial fibrillation and haemorrhagic stroke, and may increase risk of heart failure and ischaemic heart disease. There is no safe level of alcohol consumption: if you don’t currently drink, don’t start; if you do drink, it’s better to drink less.

Evidence-based public interventions to reduce harmful alcohol consumption:

  • Reduce availability (purchase age, hours and locations of sale).
  • Pricing and taxation.
  • Reducing marketing.
  • Drink driving legislation.
  • Treatment and early intervention.

Self-test

  1. List the three approaches to prevention of cardiovascular disease described in the lecture.
  2. Describe how recommended CVD interventions change across risk categories in the cardiovascular risk assessment table, from established CVD down to <5% risk.
  3. List the Heart Foundation’s nine steps to eating for a healthy heart.
  4. Explain how the DASH diet and sodium reduction each affect systolic blood pressure, and what happens when they are combined.
  5. Describe the PREDIMED trial’s design and its main finding regarding the Mediterranean diet and cardiovascular events.
  6. What did the Cochrane review of saturated fat reduction find for combined cardiovascular events, and how did risk change as the saturated fat cut-off used in studies varied?
  7. What WHO global target relates to population salt/sodium intake, and what is the WHO’s recommended maximum daily sodium intake for adults?
  8. Describe the pathway by which salt/sodium intake is thought to increase cardiovascular disease risk.
  9. List four strategies for reducing population salt intake described in the lecture.
  10. Describe the shape of the dose-response relationship between alcohol intake and coronary heart disease relative risk, including the approximate nadir and the points at which risk rises back above and beyond baseline.
  11. Distinguish the biological-plausibility arguments for a protective effect of alcohol from the reasons given for scepticism about that effect.
  12. What is the Heart Foundation’s current position on alcohol and heart health, including the quantified effect of alcohol on blood pressure risk?
  13. List the evidence-based public interventions described for reducing harmful alcohol consumption.
  14. Predict what would happen to a patient’s CVD risk-assessment follow-up interval if their calculated risk moved from 8% to 12%, based on the risk assessment table.

Answers

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