Epidemiology: time trends: practice question

A PSM question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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PSM · Epidemiology: time trends

Sample item

Before the introduction of measles vaccine, a city recorded large measles epidemics every 2 to 3 years, as susceptible children accumulated after each outbreak. This pattern is best described as a:

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Cyclic trend

Cyclic trends are regular rises and falls over periods of more than a year, as seen with measles before vaccination, because each epidemic exhausts the susceptibles and a new cohort of susceptibles then builds up. Secular trends are long-term changes over decades, and seasonal trends repeat within a year.

Option by option

  • A. Random fluctuation

    Random fluctuation lacks a regular, predictable interval.

  • B. Seasonal trend

    A seasonal trend recurs within each year, as with dengue in the post-monsoon months.

  • C. Cyclic trend (correct)

    Correct. Recurrent epidemics at intervals of a few years are a cyclic trend.

  • D. Secular trend

    A secular trend is a steady change over many years or decades, such as a long-term decline of a disease.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this PSM question

What is the answer to this PSM question?

The best answer is C, Cyclic trend. Cyclic trends are regular rises and falls over periods of more than a year, as seen with measles before vaccination, because each epidemic exhausts the susceptibles and a new cohort of susceptibles then builds up.

Why is "Random fluctuation" not the answer?

Random fluctuation lacks a regular, predictable interval.

Why is "Seasonal trend" not the answer?

A seasonal trend recurs within each year, as with dengue in the post-monsoon months.

Why is "Secular trend" not the answer?

A secular trend is a steady change over many years or decades, such as a long-term decline of a disease.

What concept does this question test?

It tests Epidemiology: time trends in PSM. Secular trends are long-term changes over decades, and seasonal trends repeat within a year.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Epidemiology: time trends?

Practise biostatistics with small calculations until sensitivity, predictive values and risk measures are automatic. Then use the flashcards and the other PSM questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.