Epidemiology, demography and vital statistics

40 M.Sc Nursing Entrance (AIIMS, LBS, PGIMER, JIPMER) practice questions on Epidemiology, demography and vital statistics, part of Community Health Nursing. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Medium

   In a case-control study of oral cancer, each case is paired with a control of the same age, sex and village. The main purpose of this matching is to:

   1. ARemove recall bias from the interviews
   2. BAllow the incidence rate to be measured
   3. CControl confounding by those factors
   4. DIncrease the number of cases studied

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   Answer: C · Control confounding by those factors

   Matching makes cases and controls alike for chosen variables that are known confounders, such as age and sex. Any remaining difference in exposure, for example tobacco chewing, is then less likely to be due to those variables. A matched factor can no longer be studied as a risk factor itself. Overmatching on a variable linked to the exposure can hide a real association.

   • A: Recall bias depends on how exposure is remembered, not on matching.
   • B: Case-control studies cannot measure incidence, matched or not.
   • D: Matching chooses controls; it does not add cases.

2. Question 2 · Hard

   A district starts mammography screening. Women whose cancer is found by screening survive a mean of 7 years after diagnosis, compared with 4 years for women diagnosed after symptoms. However, the mean age at death from breast cancer is the same in both groups. What best explains the longer survival?

   1. ALead-time bias
   2. BHigher test specificity
   3. CRecall bias
   4. DSelection of matched controls

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   Answer: A · Lead-time bias

   Screening detects disease earlier, so the clock of survival starts sooner even if the date of death does not change. The extra years are the lead time, not a true benefit, which is shown by the identical age at death. Judging a screening programme by survival from diagnosis therefore overstates its value. Mortality rates in randomised screened and unscreened populations are the proper measure.

   • B: Specificity affects false positives, not survival time after a true diagnosis.
   • C: Recall bias concerns memory of exposure in case-control studies.
   • D: Matching of controls is a case-control method and does not explain longer survival.

3. Question 3 · Medium

   A survey on one day measures both obesity and hypertension in 2,000 adults of a town. Which conclusion can this design support?

   1. AThe prevalence of each condition in the town
   2. BThe incidence of hypertension among obese adults
   3. CThe relative risk of hypertension due to obesity
   4. DThat obesity occurred before the hypertension

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   Answer: A · The prevalence of each condition in the town

   A cross-sectional survey measures exposure and outcome at the same point in time, so it gives prevalence. Because both are measured together, it cannot show which came first, so causal sequence and incidence cannot be established. It is quick, cheap and useful for planning health services. Associations it shows need cohort or experimental studies to confirm cause.

   • B: Incidence requires following disease-free people over time.
   • C: Relative risk needs incidence in exposed and unexposed groups from a cohort.
   • D: Simultaneous measurement cannot show which condition came first.

4. Question 4 · Medium

   A state records a crude birth rate of 20 and a crude death rate of 7 per 1,000 mid-year population, with negligible migration. What is its annual growth rate?

   1. A13 per cent
   2. B0.13 per cent
   3. C1.3 per cent
   4. D2.7 per cent

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   Answer: C · 1.3 per cent

   The natural growth rate is the crude birth rate minus the crude death rate: 20 - 7 = 13 per 1,000. Dividing by 10 converts a rate per 1,000 into a percentage, giving 1.3% a year. Without migration this is the whole annual growth rate. At 1.3% the population would double in roughly 70 / 1.3 = about 54 years.

   • A: 13 per cent forgets to convert from per 1,000 to per cent.
   • B: 0.13 per cent divides by 100 instead of 10 during the conversion.
   • D: 2.7 per cent adds the death rate to the birth rate instead of subtracting it.

5. Question 5 · Easy

   Sullivan's index, a composite health indicator, is calculated by subtracting from life expectancy the:

   1. AProportion of the population aged 65 years and above at the census
   2. BAverage number of days of hospital admission per person each year
   3. CNumber of years lost through deaths occurring before the age of 70
   4. DExpected duration of bed disability and inability to do major activities

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   Answer: D · Expected duration of bed disability and inability to do major activities

   Sullivan's index is the expectation of life free of disability. It is obtained by taking the probable duration of bed disability and of inability to perform major activities away from the life expectancy. It is one of the best composite indicators of health because it combines mortality and morbidity. The related DALY measures years of healthy life lost rather than healthy years expected.

   • A: The share of elderly people is a demographic indicator, not part of Sullivan's index.
   • B: Hospital days are a health-care use indicator, not a component of Sullivan's index.
   • C: Years lost through early death measure premature mortality (years of potential life lost).

6. Question 6 · Easy

   UNICEF uses which indicator as the single most important measure of the well-being of children in a country?

   1. AInfant mortality rate
   2. BLow birth weight rate
   3. CNeonatal mortality rate
   4. DUnder-five mortality rate

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7. Question 7 · Easy

   A steady decline in deaths from rheumatic heart disease in India over several decades is an example of a:

   1. ASeasonal trend
   2. BPoint-source epidemic
   3. CCyclic trend
   4. DSecular trend

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8. Question 8 · Hard

   In a stone-quarry workforce, 45 deaths occurred in a year. Applying the state's age-specific death rates to the workers' age groups gives 30 expected deaths. What is the standardised mortality ratio?

   1. A75
   2. B15
   3. C67
   4. D150

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9. Question 9 · Medium

   In a district, the incidence of a chronic skin disease is 5 per 1,000 population per year and the average duration of the illness is 4 years. If the disease is stable, its approximate prevalence is:

   1. A1.25 per 1,000
   2. B20 per 1,000
   3. C0.8 per 1,000
   4. D9 per 1,000

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10. Question 10 · Easy

    The Sample Registration System of India estimates birth and death rates by a:

    1. ATen-yearly house-to-house census of the whole population
    2. BDual record system of continuous enumeration and a half-yearly survey
    3. CCompulsory registration of every birth and death within 21 days
    4. DHospital-based record of births and deaths in government facilities

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11. Question 11 · Hard

    In a trial, 20% of patients on standard care and 15% of patients on a new drug have a stroke within two years. How many patients must be treated with the new drug to prevent one stroke?

    1. A20
    2. B5
    3. C4
    4. D7

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12. Question 12 · Easy

    Deaths of infants in the first 28 days of life, per 1,000 live births in the year, give the:

    1. AEarly neonatal mortality rate
    2. BPost-neonatal mortality rate
    3. CPerinatal mortality rate
    4. DNeonatal mortality rate

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13. Question 13 · Easy

    In the demographic cycle, India with a falling death rate and a birth rate that has begun to decline is placed in the:

    1. AHigh stationary stage
    2. BLate expanding stage
    3. CEarly expanding stage
    4. DLow stationary stage

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14. Question 14 · Medium

    To reach a net reproduction rate of 1 in India, the couple protection rate needs to be above about:

    1. A60 per cent
    2. B80 per cent
    3. C25 per cent
    4. D40 per cent

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15. Question 15 · Medium

    In a point-source (common-source, single exposure) epidemic, the epidemic curve typically shows:

    1. ASeveral peaks spaced about one incubation period apart
    2. BA single sharp peak, with all cases within one incubation period
    3. CA gradual rise over many months followed by a plateau
    4. DA low, steady number of cases throughout the whole year

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16. Question 16 · Hard

    After a hostel festival meal, 48 students develop diarrhoea. Onsets range from 10 pm to 4 am the next morning, with the median case at 1 am, and no later cases occur. The suspected agent has a median incubation period of about 12 hours. Which meal was the most likely source?

    1. ADinner at 8 pm on the festival day
    2. BLunch at 1 pm on the festival day
    3. CBreakfast at 7 am on the festival day
    4. DEvening snacks at 5 pm on the festival day

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17. Question 17 · Medium

    In a cohort study, the relative risk of lung disease from asbestos exposure is 5, and the attributable risk is 40 per 1,000 exposed workers. What does the attributable risk tell the planner?

    1. AHow many years of life each exposed worker is expected to lose
    2. BWhat proportion of the whole population is exposed to asbestos
    3. CHow much disease among the exposed would be prevented by removing exposure
    4. DHow strongly asbestos exposure is associated with the disease

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18. Question 18 · Medium

    In a case-control study of a birth defect, mothers of affected babies recall medicines taken in pregnancy far more fully than mothers of healthy babies. The resulting error is:

    1. AHawthorne effect
    2. BLead-time bias
    3. CRecall bias
    4. DBerkson's bias

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19. Question 19 · Hard

    District A has a crude death rate of 11 per 1,000 and District B of 7 per 1,000. Their age-specific death rates are almost identical, but 14% of A's population is over 60 years, compared with 6% of B's. What is the correct conclusion?

    1. ADistrict B is under-reporting deaths, because its crude death rate is lower
    2. BThe difference reflects age structure, and age-standardised rates should be compared
    3. CDistrict A has poorer health services, because its crude death rate is higher
    4. DThe two districts cannot be compared at all, because their populations differ

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20. Question 20 · Medium

    The odds ratio from a case-control study is a good estimate of the relative risk when:

    1. AThe exposure is rare in the controls
    2. BThe disease is rare in the population
    3. CThe cases outnumber the controls
    4. DThe study is done in a single hospital

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21. Question 21 · Hard

    A case-control study of 100 women with cervical cancer and 100 controls finds early marriage in 60 cases and 30 controls. What is the odds ratio for early marriage?

    1. A0.29
    2. B1.5
    3. C2.0
    4. D3.5

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22. Question 22 · Hard

    A researcher selects cases of peptic ulcer and controls with other illnesses from the wards of one tertiary hospital. Patients who have both peptic ulcer and arthritis are more likely to be admitted than those with either disease alone. The study then shows a strong link between NSAID use for arthritis and ulcer. Which bias most threatens this finding?

    1. ABerkson's bias
    2. BInterviewer bias
    3. CRecall bias
    4. DLead-time bias

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23. Question 23 · Hard

    Two screening tests for oral cancer have sensitivities of 80% and 70%, and they detect cases independently. If they are used in parallel (positive on either test counts as positive), what is the combined sensitivity?

    1. A94 per cent
    2. B56 per cent
    3. C80 per cent
    4. D75 per cent

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24. Question 24 · Medium

    In a double-blind trial of an antihypertensive drug, neither the patients nor the nurses measuring blood pressure know who is receiving the drug. This mainly prevents:

    1. ALoss of participants during the follow-up period
    2. BErrors in the calibration of the sphygmomanometers
    3. CBias from participants' and observers' expectations
    4. DUnequal distribution of confounders between groups

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25. Question 25 · Hard

    A screening test with 90% sensitivity and 95% specificity is used on 10,000 adults in a community where the disease prevalence is 2%. What is the positive predictive value?

    1. AAbout 95 per cent
    2. BAbout 27 per cent
    3. CAbout 99.8 per cent
    4. DAbout 90 per cent

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