Health, disease and the development of medicines revision notes

Diet, Exercise, Obesity and Malnutrition

Unhealthy diets (high in saturated fat, sugar, salt) and insufficient physical activity are major contributors to obesity, a condition characterised by excessive body fat. Obesity is a risk factor for NCDs such as type 2 diabetes, heart disease, and some cancers. Malnutrition encompasses both undernutrition and overnutrition. Body Mass Index (BMI) is a common tool for assessing body weight relative to height, calculated as mass (kg) / height (m)^2. A healthy BMI typically ranges from 18.5 to 24.9 kg/m². Waist-to-hip ratio also indicates body fat distribution, with higher ratios linked to increased health risks.

Alcohol and Liver Diseases

Chronic excessive alcohol consumption significantly impacts liver health. The liver metabolises alcohol, and this process can generate toxic by-products that damage liver cells. This damage can accumulate over time, leading to various liver diseases, including fatty liver disease, alcoholic hepatitis, and cirrhosis. Cirrhosis is irreversible scarring of the liver, severely impairing its function and potentially leading to liver failure or liver cancer.

Smoking and Cardiovascular Diseases

Smoking is a major risk factor for cardiovascular diseases (CVDs), which affect the heart and blood vessels. Chemicals in cigarette smoke damage blood vessel walls, promote the buildup of plaque (atherosclerosis), and increase blood pressure and heart rate. These effects can lead to conditions such as coronary heart disease, stroke, and peripheral artery disease. Smoking also reduces the oxygen-carrying capacity of blood by increasing carbon monoxide levels.

Introduction to Non-Communicable Diseases (NCDs)

Non-communicable diseases (NCDs) are medical conditions or diseases that are not caused by infectious agents. They are chronic diseases that progress slowly and are of long duration. Examples include heart disease, cancer, diabetes, and chronic respiratory diseases. A key characteristic of many NCDs is that they often result from a complex interplay of various factors rather than a single cause.

Categories of Interacting Factors

The development of NCDs is typically influenced by four main categories of interacting factors: inherited factors (genetics), lifestyle choices (diet, exercise, smoking, alcohol), environmental factors (pollution, carcinogens), and social conditions (access to healthcare, education). These factors can combine in numerous ways, increasing or decreasing an individual's risk. For instance, an individual might have a genetic predisposition to a condition, but lifestyle choices could either trigger or mitigate its onset.

Cardiovascular Diseases (CVDs)

CVDs, including heart attacks and strokes, are primarily influenced by diet high in saturated fats, trans fats, and sodium; lack of physical activity; smoking; excessive alcohol consumption; and genetic factors. High blood pressure and high cholesterol are often a result of these interactions and contribute to CVD risk.

Cancers

Many cancers result from a combination of genetic mutations (inherited or acquired) and environmental triggers. Lifestyle factors such as smoking, alcohol, poor diet, obesity, and exposure to UV radiation or certain chemicals (environmental factors) significantly increase cancer risk.

Lung and Liver Diseases

Chronic lung diseases, like emphysema and chronic bronchitis, are strongly linked to smoking (lifestyle) and air pollution (environmental). Liver diseases, such as cirrhosis, can be caused by excessive alcohol consumption (lifestyle), viral infections (though this is less common for non-communicable context), or inherited conditions (genetics).

Diseases Influenced by Nutrition

Nutritional factors play a critical role in many NCDs. Obesity, a major risk factor for type 2 diabetes, CVDs, and some cancers, is largely driven by dietary choices and lack of physical activity. Type 2 diabetes itself arises from a combination of genetic predisposition, obesity, and sedentary lifestyle.

Modes of Pathogen Transmission

Pathogens spread through various routes. Cholera bacteria are waterborne, meaning they spread through contaminated water. Tuberculosis and Chalara ash dieback are airborne, transmitting via microscopic particles or spores in the air. Malaria protists use animal vectors, like mosquitoes, to transfer from one host to another. Helicobacter pylori causes stomach ulcers and often spreads through oral transmission. Ebola virus transmission occurs through direct contact with infected body fluids.

Strategies for Prevention and Control

Preventing pathogen spread requires specific measures tailored to the transmission method. Clean water and sanitation prevent waterborne diseases like cholera. Isolating infected individuals and vaccination help control airborne diseases like tuberculosis. Restricting movement of infected material and removing diseased plants reduce the spread of Chalara ash dieback. Mosquito control and antimalarial drugs are effective against vector-borne diseases like malaria. Good hygiene and sanitation are crucial for preventing orally transmitted illnesses like those caused by Helicobacter. Strict infection control and safe handling of body fluids are vital for containing diseases like Ebola.

Specific Pathogen Examples

Cholera (bacteria) spreads via contaminated water, prevented by clean water access. Tuberculosis (bacteria) is airborne, prevented by isolation and vaccination. Chalara ash dieback (fungi) is airborne, controlled by managing diseased trees. Malaria (protists) is spread by mosquito vectors, prevented by mosquito control. Helicobacter pylori (bacteria) transmission is oral, reduced by good hygiene. Ebola (virus) spreads via body fluids, contained by strict infection control.

Understanding Pathogens

Pathogens are harmful microorganisms that cause infectious disease in their hosts. They may infect animals, including humans, or plants by damaging cells or interfering with normal functions.

Four Main Groups of Pathogens

1. Viruses: Non-cellular; reproduce by entering and hijacking host cells.
2. Bacteria: Single-celled prokaryotes; can release toxins or invade tissues.
3. Fungi: May be single-celled or multicellular; invade tissues or secrete enzymes.
4. Protists: Single-celled eukaryotes; some are parasites damaging their host from the inside.