Unit 2 Epidemiology of Chronic Diseases

READING A

PREVIEW

Chronic diseases are defined broadly as conditions that last one year or more and require ongoing medical attention or limit activities of daily living or both. Chronic diseases such as cardiovascular disease，cancer，respiratory disease，and diabetes are the leading causes of death.Chronic diseases have major adverse effects on the quality of life of affected individuals，cause premature death，and create large adverse economic effects on families，communities and societies in general.Although common and costly，many chronic diseases are also preventable.Chronic diseases do not occur at random and usually have causal risk and preventive factors that can be found.Many chronic diseases are caused by a short list of risk behaviors including tobacco use，unhealthy diet，physical inactivity，and harmful use of alcohol.If these major risk factors were eliminated，about three-quarters of heart disease，strokes，type 2 diabetes and 40%of cancers could be prevented.

Questions for Discussion

Q1：What are the differences between non-communicable diseases and communicable diseases？

Q2：What are the main strategies and actions for preventing and controlling noncommunicable diseases？

Text A　Risk Factors and Prevention of Non-communicable Diseases

Noncommunicable diseases （NCDs），also known as chronic diseases，tend to be of long duration and are the result of a combination of genetic，physiological，environmental，and behavioral factors.The main types of NCDs are cardiovascular diseases （e.g.，heart attacks and stroke），cancers，chronic respiratory diseases （e.g.，chronic obstructive pulmonary disease and asthma），and diabetes.NCDs are usually characterized by insidious onset and long duration （more than three months from diagnosis）.Additionally，they often lack clear evidence of biological causes by infectious agents and are not transmitted from person to person.

NCDs are now the leading cause of death and disability worldwide.Most chronic illnesses are unable to heal and are generally difficult to be cured completely.Some can be immediately life-threatening，such as heart disease and stroke.Others linger over time and need intensive management，such as diabetes.The epidemic of NCDs has posed devastating health consequences for individuals，families，and communities，and has been threatening to overwhelm the health systems.Cardiovascular diseases，cancer，respiratory diseases，and diabetes are among the major ones that endanger human health，decrease people's life quality，and are collectively responsible for almost 70% of all deaths worldwide.Almost three-quarters of all NCD deaths，and 82% of the 16 million people who died prematurely，or before age 70，occur in low-and middle-income countries.In China，as estimated，the loss of all-cause disability-adjusted life years （DALYs） in 2010 was 320 million person-years，of which NCDs accounted for 77%.The top five were cardiovascular disease，cancer，musculoskeletal disorders，mental and behavioral disorders，and chronic respiratory diseases.

As mentioned previously，due to the prolonged duration of chronic diseases and their unknown etiology，NCDs lead to long-term medical costs，permanent economic stress for individuals，families，societies，and countries.Therefore，the socioeconomic costs associated with NCDs make the prevention and control of these diseases a major development imperative for the 21st century.

Distribution of NCDs

NCDs have their specific features of time，population，and regional distribution.For instance，due to their long duration，the prevalence of chronic diseases has surged over time and has not yet slowed down.Prevalence also varies by country and gender.For some reason，in high-income countries，lung cancer causes more deaths among men，while deaths from breast cancer are more common among women.In contrast，in Africa，cervical cancer is the leading cancer causing a high proportion of deaths among women.However，the prevalence of NCDs is increasing rapidly in both high-income and low-income countries.The explanation for this increase is not only the rise of risk factors but also a change in diagnostic criteria.

Main Risk Factors

Diseases and other health-related events do not occur at random and usually have causal risk and preventive factors that can be found.The rise of NCDs is driven by four main risk factors：tobacco use，physical inactivity，harmful use of alcohol，and unhealthy diet.

Tobacco Use

Tobacco has been demonstrated to contain at least 250 identified harmful substances and more than 50 carcinogens.About one-sixth of mortality from NCDs can be attributed to tobacco as an exposure factor.Almost six million people die from tobacco use each year，both from direct tobacco use and second-hand smoking.By 2020，this number increased to 7.5 million，accounting for 10% of all deaths.Smoking has been estimated to be responsible for about 71% of lung cancer，42% of chronic respiratory disease，and nearly 10% of cardiovascular disease.However，tobacco consumption continues to increase rapidly in low-income and middle-income countries.To promote health，WHO recommended the adoption of the MPOWER tobacco control strategy in 2008，which includes monitoring tobacco use，protecting people against tobacco harms，providing smoking cessation assistance，warning about the harms of tobacco，banning advertising，and raising taxes，etc.

Physical Inactivity

The lack of physical activity is associated with a 20% to 30% increased risk of all-cause mortality.Regular and moderate physical activity facilitates energy balance，controls weight，builds muscle，and promotes cardiorespiratory fitness.Previous studies have demonstrated that moderate exercise reduces the risk of cardiovascular disease，diabetes，cancer，and depression.On the contrary，a sedentary lifestyle has been demonstrated to be a risk of diabetes and rectal cancer.

Harmful Use of Alcohol

Alcohol abuse is a major risk factor for premature death and disability by increasing the risk of hypertension，stroke，and other diseases.Each year，excessive alcohol abuse causes 3.3 million deaths （5.9% of all deaths）worldwide.The problem is also serious among young people：about a quarter of deaths in the 20-39 age group are caused by alcohol abuse.

Unhealthy Diet

Adequate fruit and vegetable consumption reduces the risk of cardiovascular，diseases，stomach cancer，and colorectal cancer.While on the contrary，an unhealthy diet causes at least 14 million deaths each year.Most people consume far more salt than the level recommended by WHO for disease prevention （less than five grams of salt per person per day）.High salt consumption is an important cause of high blood pressure，posing a risk for cardiovascular disease.Similarly，high consumption of saturated fats and trans-fatty acids has been linked to heart disease.

Prevention

The most frequently employed prevention strategies are population strategies and high-risk strategies.

Population strategies represent prevention approaches that target the whole population or large population subgroups.Population strategies are used where there is a mass exposure to risk，even if that risk is at a low level.Therefore，the greatest benefit will be achieved by the community by shifting the whole distribution curve.The primary methods commonly used are health education，health promotion，and community interventions.Examples of these approaches are the iodization household salt，the compulsory use of car seat belts，and increasing taxes on tobacco products，etc.

In comparison，high-risk prevention strategies target individuals or groups that made the major contribution to the incidence rate，usually due to an exposure to the presence of modifiable risk factors known to have a causal effect on the disease.Once identified，interventions are targeted to these individuals or groups to modify their risk of disease or illness.

Both of the two intervention strategies have their priorities and specificities and，in reality，need to be combined in the prevention and control of NCDs.

Three Levels of Prevention

Primary Prevention

Primary prevention aims to prevent a disease or injury before it ever occurs.For NCDs，primary prevention is usually accomplished by preventing exposure to risk factors from hazards that cause disease or injury before they occur.It is one of the fundamental measures to prevent the occurrence of chronic diseases.Generally，it contains two types：health promotion and specific prevention.Example of primary prevention includes education about healthy habits （e.g.eating well，exercising regularly，not smoking）and safety consciousness.

Secondary Prevention

Secondary prevention aims to reduce the impact of a disease or injury that has already occurred.It typically contains early detection，early diagnosis，and early treatment，with the goal of stopping or slowing the progression of the disease once it has occurred.Common measures include regular examinations and screening tests，which enable the timely detection of people undergoing the early onset of the disease and improve prognosis and prolong survival time.The frequency of the screen can be determined by demographical characteristics of the disease such as age，gender，occupation，etc.

Tertiary Prevention

Tertiary prevention focuses on softening the impact of an ongoing illness or injury that has lasting effects.It is the prevention of disability and the promotion of physiological recovery to improve a patient's function capacity，quality of life，life expectancy，as well as reduce mortality.

Words and Expressions

cardiovascular 心血管的

Coronary heart disease （CHD）is the most cardiovascular disease which damaged people's health these days.

respiratory 呼吸的

Sales of respiratory masks，spurred by swine flu，demand boosted results.

diabetes 糖尿病

People with high blood pressure are especially vulnerable to diabetes.

preventive 预防的，防备的

The authors do not address preventive interventions that occur outside the doctor's office.

stroke 卒中

She has，in the past couple of years，suffered a stroke and had heart surgery.

genetic 基因的，遗传学的

The disease has a genetic element.

physiological 生理的，生理功能的

We can get hormone levels，physiological data，disease status.

infectious 传染的，传染性的

Flu is highly infectious.

insidious 阴险的；隐伏的

Narcotics addiction is insidious.

onset 开始，发作

Most of the passes have been closed with the onset of winter.

disability 残疾，缺陷

Disability is a physical limitation on people's life.

epidemic 流行病，传染病

Today，doctors are fearing a worldwide epidemic.

consequence 后果，结果；影响

The consequences could be serious.

etiology 病因学

The most common etiology is trauma.

socioeconomic 社会经济学的

There is a known socioeconomic skew in prevalence and outcomes of cardiovascular disease.

prevalence 流行

HIV's prevalence is dropping in southern India.

cervical 子宫颈的

The cervical smear test is a lifesaver.

carcinogen 致癌物质

A carcinogen that can irritate your throat，eyes，and nose.

mortality 死亡率

Premature birth is the main cause of perinatal mortality.

sedentary 久坐的；静坐的

Obesity and a sedentary lifestyle have been linked with an increased risk of heart disease.

premature 过早的，提早的

The baby was two weeks premature.

saturated fat 饱和脂肪

Saturated fat tends to raise LDL levels.

incidence 发生率

The incidence of breast cancer increases with age.

prioritiy 优先处理的事

It did not figure high on her list of priorities.

detection 察觉，发现

Early detection of cancers is vitally important.

screening 筛选；放映

The screening tests have so far been fraught with difficulties.

prognosis 预后；预知

The prognosis of PTSD differs from individual to individual.

tertiary 第三的，第三位的，第三级的

Jobs are mainly created by the tertiary industry.

Language Point

chronic respiratory disease 慢性呼吸道疾病

Chronic respiratory disease are chronic diseases of the airways and other structures of the lung.Some of the most common are asthma，chronic obstructive pulmonary disease，respiratory allergies，occupational lung diseases and pulmonary hypertension.

Among men，exposure to this neglected risk factor nearly doubles the risk of chronic respiratory disease.

trans-fatty acids 反式脂肪酸

Trans-fatty acids are manufactured fats created during a process called hydrogenation，which is aimed at stabilizing polyunsaturated oils to prevent them from becoming rancid and to keep them solid at room temperature.

Ordering a Diet Coke with that burger and fries might ease the guilt a little，but there are still all those trans-fatty acids to worry about.

disability-adjusted life years （DALYs）伤残调整生命年

The disability-adjusted life year （DALY）is a measure of overall disease burden，expressed as the number of years lost due to ill-health，disability，or early death.

Methods disability-adjusted life years （DALY） is used as the indicator.

survival time 生存时间

It is the percentage of people in a study or treatment group still alive for a given period after diagnosis.

The median survival time was 4.0 years （1.5-8.5 years）.

life expectancy 预期寿命

Life expectancy is a statistical measure of the average time an organism is expected to live，based on the year of its birth，its current age，and other demographic factors including sex.

Metal stent placement is only indicated for patients who are intolerant of operation，or whose life expectancy is less than two years.

EXERCISES

Task 1：Vocabulary Application

Fill in the blanks with the words given below.Change the form where necessary.

1.Is it possible to manage an HIV epidemic so that ___________ stay low for long periods？

2.Researchers then estimated ___________ intake based on overall meat consumption and doneness preferences.

3.Her cancer was discovered early and her ___________ is excellent.

4.The kind of fat you should avoid is ___________ .

5.He said that he would like to see data on ___________ for the drug.

6.Wadsworth obtained a noni （诺丽果）sample and tested its juice on a friend who had___________ .

7.On the contrary，___________ lifestyle has been demonstrated to be a risk of diabetes and rectal cancer.

8.Chronic diseases do not occur at random and usually have causal risk and ___________factors that can be found.

9.NCDs are the results of a combination of ___________，physiological，environmental，and behavioral factors and usually characterized by ___________ onset and long duration.

Task 2：Writing

One of the most important ways of reducing deaths from noncommunicable diseases （NCDs）is to control an unhealthy lifestyle.For this part，you are allowed to write a composition to express your views on how to perform interventions to support behavioral self-management.You should write at least 150 words but no more than 300 words.

Flexible and stretchable wearable sensors play an important role in endowing chronic disease care systems with the capability of long-term and real-time tracking of biomedical signals.For this part，you are allowed to write a composition to express your views on the applications of wearable sensors in chronic disease care.You should write at least 150 words but no more than 300 words.

Task 3：Oral Presentation

Lifestyle medicine presents a new and challenging approach to addressing the prevention and treatment of noncommunicable diseases.The Chronic Care Model is a reasonable system of delivery to consider for lifestyle medicine，which is composed of six components that are designed to affect functional and clinical outcomes associated with chronic disease management：healthcare organization，community resources，self-management support，delivery system design，decision support and clinical information systems.Please talk about your views on lifestyle medicine.