Non-communicable diseases (NCDs) are diseases that are not transmitted directly from one person to another. They are generally chronic in nature, develop over a long period, and result from a combination of genetic, physiological, environmental, behavioural and social factors. NCDs are a major public health concern because they cause prolonged illness, disability, premature death and substantial economic losses. In epidemiology, understanding the distribution, determinants and risk factors of these diseases is essential for planning effective prevention and control programmes. The major NCDs include cardiovascular diseases, cancers, chronic respiratory diseases and diabetes, while other important conditions include chronic kidney disease, neurological disorders and mental health disorders. Cardiovascular diseases (CVDs) are among the leading causes of death and disability worldwide. They include coronary heart disease, stroke, hypertension, heart failure and other disorders of the heart and blood vessels. Coronary heart disease occurs when the blood supply to the heart muscle is reduced, commonly because of atherosclerosis. Stroke occurs when blood supply to the brain is interrupted or when a blood vessel in the brain ruptures. Hypertension is an important cardiovascular condition and also a major risk factor for heart disease and stroke. The risk factors for cardiovascular diseases can be divided into modifiable and non-modifiable factors. Non-modifiable factors include increasing age, sex, family history and genetic predisposition. Modifiable factors include tobacco use, unhealthy diet, physical inactivity, obesity, high blood pressure, high blood glucose and abnormal blood lipid levels. Excessive consumption of salt, saturated fats, trans fats and processed foods can increase cardiovascular risk. Alcohol consumption, chronic stress and inadequate sleep may also contribute. Prevention therefore focuses on healthy diets, regular physical activity, tobacco cessation, maintenance of healthy body weight and early detection and treatment of hypertension, diabetes and high cholesterol. Cancer is another major group of NCDs characterized by uncontrolled growth and spread of abnormal cells. It can affect almost any organ of the body. Common cancers include cancers of the lung, breast, oral cavity, cervix, colon and rectum, prostate and stomach. Cancer develops through a complex interaction between genetic changes and environmental or behavioural exposures. Some cancers are preventable because their major risk factors are known. Important risk factors for cancer include tobacco use, alcohol consumption, unhealthy diet, obesity, physical inactivity, exposure to ultraviolet radiation, certain infections and environmental pollutants. Tobacco is particularly important because it is associated with cancers of the lung, oral cavity, throat and several other organs. Infections with human papillomavirus are associated with cervical and some other cancers, while hepatitis B and C infections increase the risk of liver cancer. Occupational exposure to carcinogenic substances and air pollution may also increase risk. Early detection through appropriate screening and prompt treatment can reduce mortality from several cancers. Primary prevention includes tobacco control, vaccination against cancer-causing infections, healthy lifestyles and reduction of harmful environmental exposures. Chronic respiratory diseases are long-term diseases affecting the airways and lungs. Chronic obstructive pulmonary disease (COPD) and asthma are major examples. COPD is characterized by persistent respiratory symptoms and limitation of airflow and is commonly associated with long-term exposure to tobacco smoke and other harmful particles or gases. Asthma involves recurrent episodes of wheezing, breathlessness, chest tightness and coughing caused by variable narrowing of the