Strategic Approach to studying Non-Communicable Diseases (NCDs) for Community Medicine Theory Exam

Disclaimer: This article is primarily intended for my students, but is of a general nature and may be useful for others as well.

This article provides a strategic approach to studying major Non-Communicable Diseases (NCDs). The suggestions in this article are appropriate for the following conditions:

  • Cardiovascular diseases
  • Coronary heart disease
  • Hypertension
  • Stroke
  • Diabetes
  • Cancer
  • Obesity  

A strategic approach to studying NCDs listed above is possible because of the following facts:

  1. They share common risk factors
  2. Approaches to prevention are broadly similar
  3. They are covered under a single National Programme (NPCDCS)

In view of the above, one can simplify the study of NCDs as under:

Step 1: Identify common risk factors

Step 2: Classify risk factors

Step 3: Identify approaches to Primary and Secondary prevention

Step 4: Identify notable exceptions for individual conditions   

Let us consider each step in greater detail:

Step 1: Identify common risk factors

The NCDs listed above share several common risk factors. These include some factors that are non-modifiable, and others that are modifiable:

Age: In general, risk for developing NCDs increases with age.

Sex: Some conditions are more common in men, while some others are more common among women. For instance, men tend to have higher blood pressure values compared to women; and overweight/obesity is more common in women.

Ethnicity: Asians have a higher risk of developing type 2 diabetes than Caucasians, and persons of African origin are more likely to have hypertension. Ethnic variations may differ from condition to condition.

Family history: There is a genetic component to several NCDs. For instance, type 2 diabetes, and breast cancer tend to run in families.

Tobacco consumption: Perhaps the single biggest risk factor for developing NCDs, tobacco consumption in any form increases risk of developing disease and dying prematurely.

Insufficient Physical activity/Physical inactivity: While some sources mention this as physical inactivity, insufficient physical activity is more ‘accurate’. Both terms are used to describe less than 150 minutes of moderate intensity physical activity per week. However, use of the term physical inactivity is liable to be misunderstood as (complete) lack of physical activity.

Harmful use of alcohol: Although there is no safe level for alcohol consumption, harmful use of alcohol is specifically associated with development of NCDs. According to ICD-11, harmful use of alcohol refers to

‘A pattern of alcohol use that has caused damage to a person’s physical or mental health or has resulted in behaviour leading to harm to the health of others. The pattern of alcohol use is evident over a period of at least 12 months if substance use is episodic or at least one month if use is continuous.

Harm to health of the individual occurs due to one or more of the following:

  1. behaviour related to intoxication;
  2. direct or secondary toxic effects on body organs and systems; or
  3. a harmful route of administration.

Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour related to alcohol intoxication on the part of the person to whom the diagnosis of Harmful pattern of use of alcohol applies.’

Heavy episodic drinking (binge drinking, defined as 60 or more grams of pure alcohol on at least one occasion at least once per month) is also associated with increased risk for NCDs.

Unhealthy Diet: The WHO describes a healthy diet as one including the following:

  • Fruit, vegetables, legumes (e.g. lentils and beans), nuts and whole grains (e.g. unprocessed maize, millet, oats, wheat and brown rice).
  • At least 400 g (i.e. five portions) of fruit and vegetables per day, excluding potatoes, sweet potatoes, cassava and other starchy roots.
  • Less than 10% of total energy intake from free sugars, but ideally less than 5% of total energy intake for additional health benefits.
  • Less than 30% of total energy intake from fats. Unsaturated fats are preferable to saturated fats and trans-fats of all kinds. It is suggested that the intake of saturated fats be reduced to less than 10% of total energy intake and trans-fats to less than 1% of total energy intake. In particular, industrially-produced trans-fats are not part of a healthy diet and should be avoided.
  • Less than 5 g of salt (equivalent to about one teaspoon) per day Salt should be iodized.

Diets that do not conform to the above are considered unhealthy diets.

Raised blood pressure: Traditionally, a blood pressure reading of ≥140/90 mm of Hg was considered high blood pressure. The American Heart Association (AHA) now classifies systolic blood pressure >120 mm of Hg or a diastolic blood pressure of >80 mm of Hg as elevated. That is, normal blood pressure is <120/<80 mm of Hg.

Overweight and obesity: The WHO classifies body mass index (BMI) ≥25 as overweight, and ≥30 as obese. However, there are ethnic differences, and South Asians tend to develop NCDs at lower BMI values. National Institute for Care and Health Excellence (NICE) (UK) public health guidelines [ph38, and ph46] recommend BMI levels of 23 (overweight) and 27.5 (obese) for preventing type 2 diabetes mellitus in Asian populations.

Raised cholesterol: Not only is total cholesterol important, but sub-types of cholesterol are also important in determining risk for developing NCDs. Recommended levels are given below:

Itemmmol/Lmg/dL
Total (serum) cholesterol<5.0<193
Non-HDL cholesterol<4.0<155
LDL cholesterol<3.0<116
HDL cholesterolMen: >1.0
Women: >1.2
Men: >39
Women: >46
TC:HDL ratio>6 is high risk (the lower the better)>6 is high risk (the lower the better)
Table 1. Recommended levels for cholesterol

Step 2: Classify risk factors

As mentioned earlier, risk factors may be modifiable or non-modifiable. Similarly, they may be classified as agent factors, host factors, and environmental factors. The simplest approach is to classify risk factors as modifiable and non-modifiable.

It is important to note that some of the factors mentioned above are risk factors for other risk factors as well. For instance, raised blood pressure, lack of physical activity, and type 2 diabetes mellitus are risk factors for coronary heart disease.

Instead of mechanically listing risk factors, learners must highlight the most important risk factor for each disease. For instance, raised blood pressure is the single most important risk factor for development of coronary heart disease and stroke.

Step 3: Identify approaches to Primary and Secondary Prevention:

As the risk factors for most NCDs are common, approaches to prevent them are also similar. Often, approaches to reduce one risk factor tend to impact other risk factors also. For instance, approaches to reduce overweight/obesity will also impact hypertension, type 2 diabetes, cardiovascular diseases (including stroke), and some cancers. Most learners should be able to use their knowledge of common risk factors to describe appropriate preventive measures:

  • Increasing physical activity levels
  • Control of hypertension
  • Control of type 2 diabetes
  • Cessation of tobacco and alcohol use
  • Weight management/control
  • Following a healthy diet

These are appropriate for both primary and secondary prevention- when advocated before onset of disease, these form part of primary prevention; when advised after disease onset, these form part of secondary prevention. Of course, these alone are inadequate for secondary prevention- learners must be familiar with pharmacological and non-pharmacological measures as well.

One of the important aspects of secondary prevention is early diagnosis. This is ensured through screening. In most situations, high-risk screening is preferred over mass screening. Learners must be familiar with the various screening methods for specific conditions since these are disease specific.

Similarly, diagnostic criteria for individual conditions must be memorized. In conditions like hypertension and overweight/obesity, problem-solving questions may provide limited information based on which students must make a diagnosis and plan management. To answer such questions, students must be familiar with disease classification, so that they may correctly identify the severity of the condition. Neglecting to pay attention to this detail may result in incorrect diagnosis and case management.

Step 4: Identify notable exceptions for individual conditions:

While the above points and tips work well for most NCDs, students must beware of notable exceptions. For instance, cervical cancer is more common in women of lower socio-economic class, while breast cancer is commoner among those from higher socio-economic classes.

Similarly, while physical activity has an inverse relationship with occurrence of breast cancer (higher physical activity lowers risk of developing and surviving breast cancer), no such relationship has been established for cervical cancer. However, obesity is a risk factor for both breast cancer and cervical cancer.

Familiarity with exceptions will help avoid common pitfalls in the examination.

Note 1. Step 1 and Step 2 are interchangeable- the order does not matter.

Note 2. Those who are already familiar with Steps 1 and 2 may combine them.

Note 3. This approach is intended to help weak students write reasonable answers to most questions pertaining to Non-Communicable Diseases- it may be unsuitable for strong students as their knowledge level and expectations are likely to be higher.    

Useful Links:

Link to previous article on strategic approach to studying communicable diseases:

https://communitymedicine4all.com/2021/05/04/strategic-approach-to-studying-communicable-diseases-for-community-medicine-theory-exam/

Link to ICD-11 description of harmful pattern of use of alcohol:

https://icd.who.int/browse11/l-m/en#/http://id.who.int/icd/entity/714690795

Link to WHO Global Status Report on Alcohol and Health (2018):

https://apps.who.int/iris/bitstream/handle/10665/274603/9789241565639-eng.pdf?ua=1

Link to WHO fact sheet on healthy diet:

https://www.who.int/news-room/fact-sheets/detail/healthy-diet

Link to American Heart Association fact sheet on blood pressure:

https://www.heart.org/en/health-topics/high-blood-pressure/the-facts-about-high-blood-pressure

Link to NICE guidance on BMI:

https://www.nice.org.uk/guidance/ph46/chapter/1-recommendations#:~:text=In%202004%2C%20the%20World%20Health,were%20appropriate%20for%20Asian%20populations.

Link to Indian Heart Association page on Cholesterol levels for South Asians:

http://indianheartassociation.org/cholesterol-and-south-asians/

Link to American Heart Association page on Cholesterol levels:

https://www.heart.org/en/health-topics/cholesterol/about-cholesterol/what-your-cholesterol-levels-mean

Links to articles on relationship between physical activity and breast cancer:

https://pubmed.ncbi.nlm.nih.gov/30780085/

https://www.jstor.org/stable/20486329?seq=1

Links to articles on relationship between obesity and cervical cancer:

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