Investigate the causes and effects of named nutritional and environmental diseases, including diabetes (type 2), cardiovascular disease and mesothelioma

What this dot point is asking

NESA wants you to describe the causes, mechanisms and effects of named nutritional and environmental diseases. Type 2 diabetes, cardiovascular disease and mesothelioma cover the three main categories: metabolic-nutritional, lifestyle-related and toxic environmental exposure.

The answer

Type 2 diabetes mellitus

Burden. Approximately 1.3 million Australians have type 2 diabetes (T2DM); around 5 percent of adults. The number is rising with obesity rates.

Causes.

• Genetic. Family history doubles risk. Susceptibility variants in TCF7L2, KCNQ1 and others.
• Lifestyle. Obesity (BMI over 30), sedentary behaviour, energy-dense diets high in refined carbohydrates and saturated fats.
• Demographic. Age over 45, certain ancestries (Indigenous Australian, South Asian, Pacific Islander).
• Gestational diabetes. History increases lifetime risk.

Mechanism. Insulin normally binds receptors on muscle, liver and fat cells, triggering glucose uptake via GLUT4 transporters. In T2DM, intracellular fat metabolites and inflammatory signalling impair insulin receptor signalling, producing insulin resistance. Beta cells compensate by hypersecreting insulin; over years they exhaust, glucose rises, and diabetes appears.

Effects. Chronic hyperglycaemia non-enzymatically glycates proteins, damaging blood vessel walls.

• Microvascular. Retinopathy, nephropathy, peripheral neuropathy.
• Macrovascular. Heart attack, stroke, peripheral vascular disease.
• Other. Foot ulcers and amputation, recurrent infection, NAFLD, dementia risk.

Cardiovascular disease

Burden. Cardiovascular disease (CVD) is the leading cause of death in Australia, killing approximately 42 000 people each year. It includes coronary heart disease, stroke, heart failure and peripheral vascular disease.

Causes (risk factors).

• Modifiable. Smoking, hypertension, dyslipidaemia (high LDL, low HDL), diabetes, obesity, sedentary behaviour, poor diet, excess alcohol, chronic stress.
• Non-modifiable. Age, male sex, family history, certain ancestries.

Mechanism: atherosclerosis.

1. Endothelial injury. LDL cholesterol, hypertension, smoking and high glucose damage the arterial endothelium.
2. LDL infiltration. LDL enters the intima and is oxidised.
3. Foam cell formation. Macrophages engulf oxidised LDL, becoming foam cells.
4. Plaque growth. Smooth muscle cells migrate and proliferate. A fibrous cap forms over a lipid-rich necrotic core.
5. Stenosis or rupture. Plaques narrow the artery, reducing blood flow (angina). Rupture exposes the necrotic core to blood, triggering thrombosis. A coronary thrombus causes myocardial infarction (heart attack); a cerebral thrombus causes ischaemic stroke.

Effects.

• Angina pectoris. Chest pain on exertion due to coronary artery narrowing.
• Myocardial infarction. Death of cardiac muscle from sustained ischaemia.
• Heart failure. Loss of cardiac output capacity after infarction.
• Stroke. Loss of brain function from cerebral artery occlusion.

Management.

• Lifestyle. Smoking cessation, dietary change (Mediterranean, DASH), exercise, weight loss.
• Pharmaceutical. Statins (lower LDL), antihypertensives (ACE inhibitors, beta blockers), antiplatelets (aspirin, clopidogrel), anticoagulants in selected cases.
• Procedural. Coronary angioplasty with stenting, coronary artery bypass grafting (CABG), valve replacement.

Mesothelioma

Burden

Australia has one of the highest mesothelioma incidence rates in the world (around 700 to 800 cases per year), driven by extensive historical asbestos use in construction and at the Wittenoom blue asbestos mine in Western Australia (operational until 1966).

Cause

Inhalation or ingestion of asbestos fibres (chrysotile, crocidolite, amosite). Less common: erionite (a similar fibrous mineral) and high-dose radiation.

Mechanism

Detailed in the past-question answer above. Fibres lodge in the pleura, generate chronic inflammation and reactive oxygen species, and mutate tumour suppressor genes (BAP1, NF2, CDKN2A). Latency is 20 to 50 years.

Effects

Malignant pleural mesothelioma presents with chest pain, breathlessness from pleural effusion, weight loss and fatigue. The cancer is largely confined to the pleural cavity but is invasive, encasing the lung and resisting surgical removal. Peritoneal mesothelioma is less common and affects the abdominal cavity.

Management

Largely palliative. Pleurectomy and extrapleural pneumonectomy in selected patients. Chemotherapy with pemetrexed plus cisplatin. Immunotherapy (nivolumab plus ipilimumab) extends median survival modestly. Median survival from diagnosis remains under 12 months.

Prevention

Asbestos was progressively banned in Australia from 1989; total ban in 2003. Home renovators remain at risk; pre-1990 buildings should be tested before renovation.

Other nutritional and environmental diseases (worth knowing)

Iodine deficiency

Causes goitre and congenital cretinism. Reduced markedly in Australia by iodised salt and iodised baker's flour.

Folate deficiency

Causes neural tube defects in fetuses. Reduced by mandatory folate fortification of bread flour (Australia, 2009).

Vitamin D deficiency

Causes rickets in children and osteomalacia in adults. Reappearing in heavily veiled or housebound populations.

Lead poisoning

Causes neurological damage in children. Reduced by removal of lead from petrol (1986 to 2002) and house paint.

Air pollution

PM2.5 from traffic and bushfires causes COPD and ischaemic heart disease. Black Summer (2019 to 2020) bushfire smoke caused approximately 400 excess deaths in eastern Australia.

Examples in context

Example 1. Mesothelioma in James Hardie former employees and the asbestos register. James Hardie Industries manufactured asbestos cement products at sites including Camellia in Sydney's western suburbs from the 1930s to the 1980s. Former workers who inhaled crocidolite or chrysotile fibres typically developed mesothelioma 30 to 50 years later. Fibres less than 5 microns long penetrate alveoli and are translocated to the pleura, where they cannot be cleared and induce chronic inflammation and DNA damage in mesothelial cells. The Australian Mesothelioma Registry tracks roughly 700 new cases per year, with median survival under 12 months from diagnosis. The James Hardie compensation fund, established in 2007 after extensive litigation, provides ongoing support to affected workers and their families.

Example 2. Atherosclerosis in a 55-year-old Sydney commuter. A NSW Health typical cardiovascular case is a 55-year-old man with LDL cholesterol of 4.5 mmol/L, blood pressure 145/95, BMI 31 and a 30-pack-year smoking history. Over 30 years, oxidised LDL particles infiltrate the intimal layer of his coronary arteries, attract macrophages that engulf LDL to become "foam cells", and develop into atheromatous plaques. As plaques grow, they narrow the coronary lumen and the endothelium becomes vulnerable to rupture. A plaque rupture exposes thrombogenic material, a clot forms, blood flow to a section of myocardium ceases, and the patient has a myocardial infarction. Management uses statins, antihypertensives, and lifestyle change, addressing the multiple modifiable risk factors simultaneously.

Try this

Q1. Distinguish between type 1 and type 2 diabetes by cause and treatment. [3 marks]

• Cue. Type 1: autoimmune destruction of pancreatic beta cells, requires insulin. Type 2: insulin resistance from obesity and inactivity, treated with lifestyle change, metformin, sometimes insulin.

Q2. AIHW data show Australian cardiovascular disease mortality fell from 380 per 100 000 in 1980 to 70 per 100 000 in 2024. If the 1980 population was 14.7 million, calculate the absolute number of deaths in 1980 and identify three contributing factors to the decline. [3 marks]

• Cue. Deaths in 1980: 380 by 147 = ~55 860. Factors: tobacco reduction, statin therapy, blood pressure control, emergency revascularisation (stents, thrombolysis).

Q3. Evaluate the role of environmental versus lifestyle factors in non-infectious disease. (a) Identify one disease primarily environmental. (b) Identify one disease primarily lifestyle-driven. (c) Justify whether mesothelioma or type 2 diabetes is more amenable to public health intervention. [2+2+3 marks]

• Cue. (a) Mesothelioma (asbestos). (b) Type 2 diabetes (diet, activity). (c) Both preventable but type 2 diabetes requires sustained behaviour change; mesothelioma requires regulatory action (asbestos bans).