0900L - NON-COMMUNICABLE DISEASE

Copyright by Professor Omar Hasan Kasule Sr.

MODULE OUTLINE

10.1 EPIDEMIOLOGICAL CHARACTERIZATION

10.1.1 Over-view

10.1.2 Incidence Trends

10.1.3 Causes

10.1.4 Disease Processes

10.1.5 Prevention & Control

10.2 RISK FACTORS

10.2.1 Nutrition:

10.2.2 Alcohol:

10.2.3 Tobacco 

10.2.4 Physical Inactivity:

10.2.5 Environmental Factors:

10.3 CANCER

10.3.1 Incidence and Mortality

10.3.2 Cancer Sites

10.3.3 Risk Factors

10.3.4 Cancer Prevention

10.4 DISEASES BY ORGAN SYSTEM

A. Cardio-Vascular and Respiratory Disorders

B. Psychiatric and Neurological Disorders

C. Gastro-intestinal and Genito-Urinary Disorders

D. Traumatic and Musculo-skeletal Disorders

E. Other Disorders

10.5 DISEASES BY AGE GROUP

A. Intra-uterine Disorders

B. Maternal Disorders

B. Infant and Child Disorders

C. Adolescent Disorders

D. Disorders of the Elderly

UNIT 10.1

EPIDEMIOLOGICAL CHARACTERIZATION OF NON-COMMUNICABLE DISEASES

Learning Objectives

·         Definition and characteristics of non-communicable disease

·         Incidence trends

·         Risk factors

·         Prevention and control

Key Words and Terms

• Disease, Chronic Diseases
• Disease, Non-Communicable Disease
• Disease, Degenerative Disease
• Multiple Causes
• Prolonged Course
• Spontaneous Resolution
• Rare Complete Cure
• Non Transmissibility
• Specific Cause-Disease Relation
• Long Latency
• Transition, Ecological
• Transition, Demographic
• Transition, Epidemiologic
• Disease Burden
• Life Expectancy
• Risk Indicators
• Risk Factors
• Preventative Intervention
• Final Common Path
• Genetic Causes
• Environmental Causes
• Lifestyle
• Primary Prevention
• Secondary Prevention
• Tertiary Prevention
• Human behavior and lifestyle
• Years Of Potential Life Lost
• Economic Cost Of Disease
• Control
• Intervention
• Community Norms
• Enhancing Knowledge & Skills
• Screening & Follow-Up

UNIT OUTLINE

10.1.1 DEFINITIONS

A. Characteristics of Non-Communicable Diseases

B. Communicable vs. Non-Communicable Disease

10.1.2 INCIDENCE TRENDS

A. Data Limitations

B. Changing Patterns

C. Disease Burden

10.1.3 CAUSES

A. Unknown Causes

B. Preventive Action Based on Incomplete Knowledge

C. Multiple Causes

D. Life Style

10.1.4 DISEASE PROCESSES

A. Neoplasm

B. Inflammation

C. Degeneration

D. Metabolic and endocrine

E. Others

10.1.5 PREVENTION & CONTROL

A. Definition and Types of Prevention

B. Human Behavior and Life Style

C. Setting Preventive Priorities

D. Control

E. Intervention

10.1.1 DEFINITIONS

A. CHARACTERISTICS OF NON-COMMUNICABLE DISEASES

Chronic diseases (non-communicable, degenerative disease) are defined by the following characteristics: multiple causes, a prolonged course, lack of spontaneous resolution, rare complete cure, and non transmissibility from the victim to the susceptible. The prolonged course of these diseases depletes community and personal resources. The distinction between communicable & non-communicable is becoming blurred because diseases thought before to be non-communicable have now been found to have an infective etiology. Viruses have been implicated in neoplastic and chronic neurological diseases. The H. pylori bacterium has been implicated in chronic peptic ulceration.

B. COMMUNICABLE vs. NON-COMMUNICABLE DISEASE

Communicable diseases have a single defined necessary cause specific for the disease. Non communicable diseases are multi-causal, the causes are not known definitively, and the cause-disease relation is seldom specific. Communicable diseases result from a single exposure and cause acute disease after a short incubation period. Non communicable diseases have a long latency and chronic disease follows repeated exposures to the agent. A communicable disease is followed by acquired immunity but non communicable diseases are not. Diagnosis of a communicable disease is based on an agent-specific test. Diagnosis of a non-communicable disease is based on non-specific symptoms and signs.

10.1.2 INCIDENCE TRENDS

A. DATA LIMITATIONS

Data on chronic diseases is limited, incomplete, and inaccurate. This is more marked in developing countries where diagnostic and treatment facilities are inadequate. Reporting systems are not complete. Observed incidence trends may be due to differences in disease ascertainment. Epidemiologists therefore have to labor under the constraints of insufficient data in their analysis of disease occurrence and planning of intervention strategies.

B. CHANGING PATTERNS

Changing patterns in the incidence of non-communicable diseases have been observed over the past century. These are explained by ecological, demographic, and epidemiologic transition. There is a general increase in incidence explained by the relative decrease of infectious diseases as competing causes of death, an ageing and older population, a more complex society causing stress and depression, environmental pollution due to increased industrialization and disturbance of the natural eco-system, better detection and diagnostic characterization. The overall increase in incidence of non-communicable diseases is not uniform. Economically developed countries are experiencing a more rapid increase. Even within the same country, there are different trends in different population sub-groups.

C. DISEASE BURDEN

Non-communicable diseases are responsible for much disease burden. Complete elimination of all cancer would result in a gain of 2.5 years in life expectancy. Complete elimination of all IHD would result in a gain of 6 years. Elimination of infectious disease would result in a gain of 10 years. The average number of years of life lost due to all cancers is 15.3 years being distributed as follows: prostate cancer 9.3, lung cancer 14.9 years, female breast cancer 19.4 years, testicular cancer 36.4, and lethal childhood malignancies 68.8 years.

10.1.3 CAUSES

A. UNKNOWN CAUSES

The causes of most non-communicable diseases are not known definitively. Epidemiologists have identified putative risk indicators and risk factors. More studies are needed before definitive conclusions.

B. PREVENTIVE ACTION BASED ON INCOMPLETE KNOWLEDGE

Preventive action in public health does not have to wait for complete understanding of the causative factors. Preventative intervention is based on eliminating or modifying the suspected risk factors. In most cases definitive conclusions about causality emerge from the results of successful intervention. With the growth of molecular epidemiology, more will be learned about the risk factors and more effective interventions will become possible.

C. MULTIPLE CAUSES

Virtually all non-communicable diseases have multiple causes. The disease is the final path of interactions among genetic and environmental factors. Economic and personal factors also play their roles.

D. LIFE STYLE

Non-communicable diseases are closely associated with life style. The following are termed diseases of civilization because they are associated with the modern life style: appendicitis, gall stones, diverticulosis, ischemic heart disease, cancer of the colon, hiatus hernia, and varicose veins.

10.1.4 DESCRIPTION OF THE DISEASE PROCESS

A. NEOPLASIA:

PATHOLOGY

Much progress has been achieved in cancer biology in the past decade. We know a lot about carcinogenesis but our knowledge is still incomplete. Rapid advances in cell biology hold a lot of promise for the future. There is good undetstanding of the processes of cell neoplasia, anaplasia, heterotopia, atypism, polymorphism, metastasis, and the carcinogenic process that concerts a stem cell into a malignant cell. Pre-cancerous lesions like dysplasia precede malignant neoplastic change. These may stop and regress or may develop into frank malignancy. Neoplasms can be divided into benign and malignant. Benign neoplasms retain many features of the original cells; ie they are well differentiated. Their growth is slow and they do not invade local tissues or spread to distant sites. Malignant tumors on the other hand are rapidly growing, poorly differentiated, and are invasive. Malignant tumors are at different degrees of differentiation; the most undifferentiated are the most malignant and the most difficult to treat. The degree of malignancy can be understood as the degree of moving away from the normal. The neoplastic cells may be monoclonal or polyclonal. Monoclonal cells arise from one single cell that becomes neoplastic and proliferates. Poly-clonal malignancies arise from several initial malignant cells. Monoclonal malignancies thus show more homogeneity that polyclonal ones. The difference between monoclonal and polyclonal malignancy is important in understanding causality and response to treatment. The neoplastic process is essentially loss of control of cell growth; it is biological anarchy. The neoplastic cell replicates faster that a normal cell. It loses the important characteristic of contact inhibition and therefore does not stop growing when it comes in contact with adjacent cells. The neoplastic cells may invade local tissues or may spread, metastasize, to other parts of the body. The primary site of a neoplasm is the tissue where malignant change first occurs. The secondary site is where the malignancy metastasizes. Malignant proliferation continues in the secondary sites. Malignant tumors are of three categories: carcinomas, sarcomas, leukemias and lymphomas. Carcinomas are neoplasms of epithelial tissues, the endodermal and the ectodermal. More than 85% of malignant neoplasms are carcinomas (ie epithelial origin). This explains why the term cancer is used for all malignancies although it strictly refers to epithelial neoplasms only. Sarcomas are from mesodermal tissues. Leukemias and lymphomas are from cells of the bone marrow and the immune system. Symptoms and signs due to malignancy may be due to local pressure effects or may be systematic effects. Systemic effects may be due to pressure effects, destruction of vital organs such as the bone marrow and endocrine glands, or overwhelming the circulatory and excretory systems with many malignant cells. Some neoplasms produce systemic effects by secreting chemicals such as enzymes or hormones.

STAGING

A systematic staging system for each neoplasm is agreed on internationally to enable communication. It is called the TNM system because it is based on the Tumor bulk, Nodal involvement and existence of Metastasis. TNM staging is used to determine the type of treatment and also to forecast prognosis. 

TUMOR MARKERS

Tumor markers are used in the diagnosis and assessment of prognosis for some malignancies. The commonest ones are oncofetal antigens, placental products, and isoenzymes. Alpha feto protein is an oncofetal antigen used in hepatocellular carcinoma. Placental alkaline phosphate is a placental product used in carcinoma of the ovary. Acid phosphatase is an isoenzymes used in carcinoma of the prostate.

ETIOLOGY

The etiology of cancer is multi-factorial and is poorly understood. There is a variable interaction between environmental and genetic factors. Some cancers are due to genetic factors independent of any environmental factors. Some cancers are due to a single autosomal dominant gene. Familial retinoblastoma is a good example. Some cancers are due to environmental factors with no involvement if any genetic factors for example lung cancer due to cigarette smoking, leukemia due to irradiation, and oral cancer due to alcohol consumption. A third group of cancers is due to the joint effect or interaction of genetic and environmental factors. These cancers are due to autosomal recessive genes. A fourth group of cancers is independent of both environmental and genetic factors and occurs by spontaneous mutation. The search for cancer determinants has involved both the epidemiological and experimental approaches. The following epidemiological observations give a clue to cancer causes: variation of cancer risk by socio-ethnic and geographical factors, change in cancer incidence in migrant groups, and change of incidence rate with time. The experimental approach involves testing putative carcinogens in animals and cultured cells. Epidemiological and laboratory studies suggest two established causes of cancer: irradiation and tobacco. Ultra-violet irradiation leads to basal cell carcinoma and melanoma. Exposure to ionizing radiation occurs medially, industrially, or in atomic bombing. Irradiation leads to malignancy by chromosomal damage. Irradiation is involved in the cancers of the breast, leukemia, and the thyroid. Tobacco in cigarettes leads to lung cancer. Studies suggest the following presumptive causes: chemicals, viruses, diet, alcohol, drugs, and genetic effects. Chemical carcinogens include polycyclic hydrocarbons e.g. in cigarettes, aromatic amines in aniline dyes, nitrosamines in food, toxins like aflatoxin, and alkylating agents used in cancer chemotherapy. RNA retroviruses are involved in HTLV and HIV related diseases. DNA viruses are involved in Burkitt's Lymhoma, Nasopharyngeal carcinoma, and hapato-cellular carcinoma. Evidence of dietary association with several cancers is strong but is not specific enough. Alcohol is involved in liver and esophageal cancers. Several cancers display a hereditary basis.

B. INFLAMMATION:

Inflammation may be infective or non-infective. Examples of infective inflammatory disease are: rheumatic heart disease due to delayed effects of the childhood beta hemolytic streptococcal throat infection; Chagga’s heart disease due to trypanosoma cruzi, and syphilitic heart disease.

Acute inflammation may turn into chronic inflammation. It is the chronic irritation of such inflammation that leads to several diseases. The common chronic inflammatory conditions are: chronic ulcers, chronic bronchitis, emphysema, and asthma. Chronic tropical ulcers turn into squamous cell carcinoma of the skin. Chronic bronchitis, emphysema, and asthma are chronic inflammatory conditions. There is no universally agreed definition of chronic bronchitis and emphysema. The two terms are used interchangeably. The natural history of emphysema/bronchitis starts with bronchial irritation or bronchial hypersensitivity due to occupational exposure to dusts (mineral and organic), chemicals, biological agents, and radiation. Smoking interacts synergistically with occupational exposure. Mucous hypersecretion and recurrent infection follow this. It ends as irreversible bronchial obstruction. Respiratory failure in bronchitis and emphysema is when the oxygen arterial pressure is low. There is no agreed definition of asthma. Child-hood onset asthma is outgrown by puberty. Little is known about adult-onset asthma.

C. DEGENERATION:

OVER VIEW

Degenerative changes occur as a function of time or longevity. The longer humans live the longer they are exposed to environmental insults that damage the body tissues. Some forms of damage are not due to external factors but arise spontaneously as metabolic or genetic disorders. Thus the statistical probability of cellular or tissue damage rises with age. At younger ages, any tissue damage can be repaired easily. With advancing age the reparative processes become impaired so that any damage once sustained is likely to turn into disease. The following are the commonest degenerative conditions: atherosclerosis leading to coronary heart disease (CHD), Alzheimer's disease, osteoporosis, and osteoarthritis.

ATHEROSCLEROSIS

Atherosclerosis occurs often with hypertension and their effects may be confounded. Atheroma affects arteries of medium or large size. It starts in childhood with fatty streaks that become localized fatty plaques in the 3^rd decade of life and start bulging into the lumen of the blood vessel. This is followed by obstruction and narrowing. There are episodes of fissuring, rupture, embolization, thrombus formation, thrombus organization, and scarring. Atherosclerosis affects the abdominal aorta, the arteries of the neck, and arteries of the base of the brain, and coronary arteries. Atherosclerosis of the abdominal aorta causes abdominal aneurisms. Athesclerosis of the base of the brain causes stroke. Athesclerosis of the iliac and leg arteries cause peripheral vascular disease. Athesclerosis of the coronary arteries causes coronary artery disease. Coronary arteries are end arteries with limited collateral circulation. The terms coronary artery disease (CHD), ischemic heart disease (IHD), and atheromatous heart disease (ASHD) are used interchangeably. CHD is not a new disease. It is an epidemic that started in the 1920s. CHD, a progressive disorder due to obstruction of the coronary arteries by cholesterol-rich fibro-fatty deposits, causes fibrillation, and thrombosis leading to infarction. Manifestations of CHD are angina pectoris, chronic heart failure, and sudden death due to myocardial infarction. Angina arises on effort and is ischemic chest pain that results on increased cardiac work and thus higher oxygen demand. It is treatable medically by trinitrin, beta  blockers, calcium blockers, long acting nitrates, and aspirin. It is treatable surgically by coronary artery bypass graft (CABG) and percutaneous coronary angioplasty (PTCA). Chronic ischemia may lead to impaired cardiac pump efficiency with limited exercise tolerance, which is known as chronic heart failure. An ischemic attack is preceded by prodromal symptoms of chest pain; dyspnea, tiredness, but they have low predictive value. It is treatable by defibrillation, aspirin, and anti-coagulants.

OSTEOPOROSIS

Osteoporosis is absolute decrease in the amount of skeletal bone. It is a personal health hazard especially in menopausal women because it leads to fractures. There is an ethnic variation. Whites are more affected than Asians. Blacks have an earlier peak bone density. Hormonal disturbances are usually involved: hyperthyroidism, hyper-parathyroidism, hyperactive corticolemia, and hypopituitarism. Low calcium intake, gastric or bowel resection, malabsorption, anorexia nervosa. Post-menopausal osteoporosis occurs 10-15 years after menopause. It is associated with crush fractures of the vertebrae, fracture of the lower fore arm, loosening of teeth. It is due to decreased calcium absorption because of hormonal imbalances. Senile osteoporosis causes widespread fractures due to the aging process.

D. METABOLIC AND ENDOCRINE

Many endocrine and metabolic disorders have been described in the past half-century. Diabetes mellitus is the most common and most important from the epidemiological perspective. DM was originally defined as the syndrome of polyuria, polyphagia, wasting, coma, and death. Later it was defined as chronic hyperglycemia. Two forms of this syndrome can be distinguished: insulin and non-insulin dependent diabetes mellitus. Insulin-dependent diabetes mellitus (IDDM) is the most severe form and occurs early in life. Non-insulin-dependent diabetes (NIDDM) occurs in obese and non-obese persons. Non-insulin dependent diabetes is mature-onset. Obesity plays a role in IDDM but may have no role in NIDDM. Among the complications of DM is diabetic retinopathy leading to blindness and cataracts. Renal complications. Arterial disease. Impaired glucose tolerance as measured by GTT and other types of hyperglycemia are found in non-diabetic disorders: malnutrition, pancreatic disease, hormonal influences, drug-induced, abnormal insulin receptors, gestational diabetes, and genetic syndromes. Metabolic disorders of carbohydrate, protein, and lipid metabolism are usually due to hereditary factors.

E. OTHERS

TRAUMA

Traumatic injury occurs in all human activities: at work, at home, and during recreation. The most serious traumatic injury is sustained in road traffic accidents (RTA). Injury of motor vehicle occupants is due to sudden deceleration. Industrial accidents are increasing. There are new forms of traumatic injury that are being described such as the injury to the hand tendons due to repetitive work.

PSYCHIATRIC DISORDERS

The organic basis of psychiatric disorders was suspected following the discovery of effective psychotropic medication. The organic mechanisms of many such disorders are becoming unraveled. There is however a core of psychiatric disorders for which an organic basis may not be found because they have to do with innate disturbances of the human psyche or nafs. DSM (diagnostic and statistical manual) of the American Psychiatric Association has specific but arbitrary criteria for classification of psychiatric disorders. It is backed up by a questionnaire that can be scored. Schizophrenia and depression are the commonest psychiatric disorders. Schizophrenia, besides being an economic burden and a source of family stress, leads to a marginalized life, poverty, homelessness, and higher risk of imprisonment. Depression has both somatic and psychological symptoms. It is an economic burden.

ORAL DISEASE

Oral diseases impair speech and eating in addition to causing disfigurement and pain. Dental caries are caused by acid-producing bacteria that lead to progressive decalcification of the dental enamel leaving a cavity called a dental cary. Most oral bacteria are cariogenic. Frequent ingestion of carbohydrates provides a substrate for the bacteria.

10.1.5 PREVENTION & CONTROL

A. DEFINITION AND TYPES OF PREVENTION

Prevention is defined as intervention before or early in disease. Primary prevention prevents occurrence. Secondary prevention shortens the duration of disease. Tertiary prevention prevents complications. Primary prevention is essentially is creating a pro-health anti-disease situation in the individual and the community. It includes general measures of adequate food supplies, education, employment, housing and other necessary community infrastructure and services. More specific measures include health promotion, health education, health care services, and protection from environmental hazards. At the individual level primary prevention includes proper nutrition, health knowledge, exercise, avoiding addictions to alcohol and drugs, and following all recommended safety measures such as seat belts. Secondary prevention at the community level consists of mass disease screening, case finding,  and early appropriate medical care. The individual can undertake personal screening such as BSE, testicular examination, hemoccult test, pap smear, glaucoma tests, BP checks, and regular dental check-up. Screening for early detection and treatment is effective for some diseases and not others. Pap smear screening of women can prevent cervical cancer. A screening program consisting of breast examination and mammography can prevent breast cancer. Environment action is directed against water pollution, soil, and air pollution.  Tertiary prevention consists of providing the necessary hospital facilities, medication compliance, exercise, and diet.

B. HUMAN BEHAVIOR and LIFE STYLE

Epidemiological knowledge available today is sufficient to make a major impact on many diseases. Persuasion of people to change their behavior is not enough. Consideration of using more coercive legislative measures violates the basic human rights of freedom of choice. The matter becomes more complicated when the rights of the individual have to be considered against the welfare of the general society. Most non-communicable diseases can be prevented by changes in human behavior or lifestyle. This is the Achilles' heel of epidemiology and public health because human behavior is very complex. It is difficult to fully understand what motivates humans to engage in some life-style activities and not others. It is even more difficult to understand how to change such behavior. In the US in 1987 73.5% of all disease due to the triad of tobacco, alcohol, & poor nutrition. The picture today in the US and other developed countries is not much different. The same scenario is developing fast in developing countries as communicable diseases get under control. The preventive possibilities lie in changing life style and behavior, early detection and treatment of disease, and environmental improvements. Changing of life-style and behavior is directed at smoking, diet, and physical inactivity.

C. SETTING PREVENTIVE PRIORITIES

Resources available for disease prevention are limited. Some criteria must therefore be adopted to prioritize which diseases to start with in control. Generally three criteria are used: number of deaths from the disease, years of potential life lost, and the economic cost of the disease. The biggest causes of death in industrialized countries are: cardio-vascular disease, cancer, COPD, and accidents. The years of potential life lost, YPLL, is calculated by subtracting the age at death from 65. Economic data is needed to compute the economic cost of a disease. This includes lost earnings and money spent caring for the patient.

D. CONTROL

Control is defined as measures taken later in course of disease to reinforce preventive measures. The goals of chronic disease control are: Reduce incidence rate, Alleviate severity, Delay onset, Improve quality of remaining life, Change public attitude from inevitability to preventability, adopting healthy life-style.

E. INTERVENTION

Intervention against disease can be at the level of the individual or the community. The public health approach is directed at the community. The approaches used in intervention are primary prevention, early detection, treatment, and management of complications. The basic principles of intervention are: changing community norms, community involvement, formulating clear objectives, targeting specified populations, using multiple interventions that are locally relevant, and undertaking on-going evaluation with preparedness to change course if no results are seen. The strategies of disease control are modifying community norms, enhancing knowledge & skills, and screening & follow-up. The channels used in control programs are health-care system, schools, work sites, NGOs, and the media. The steps in the control process are review of health, demographic, economic, social, environmental conditions, definition of problems, definition of the target population, selection of the channel, choice of the strategy, preparing and piloting a plan, and then generalizing. Outstanding problems: No complete data, Application of biomedical knowledge, and Human behavior.
<read more>