A two-year study beginning in 1977 found that, among 85-year-old people, those whose immune systems were weakest were twice as...

GMAT Critical Reasoning : (CR) Questions

Source: Official Guide

Critical Reasoning

Paradox

MEDIUM

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A two-year study beginning in 1977 found that, among 85-year-old people, those whose immune systems were weakest were twice as likely to die within two years as others in the study. The cause of their deaths, however, was more often heart disease, against which the immune system does not protect, than cancer or infections, which are attacked by the immune system.

Which of the following, if true, would offer the best prospects for explaining deaths in which weakness of the immune system, though present, played no causal role?

There were twice as many infections among those in the study with the weakest immune systems as among those with the strongest immune systems.

The majority of those in the study with the strongest immune systems died from infection or cancer by 1987.

Some of the drugs that had been used to treat the symptoms of heart disease had a side effect of weakening the immune system.

Most of those in the study who survived beyond the two-year period had recovered from a serious infection sometime prior to 1978.

Those in the study who survived into the 1980s had, in 1976, strengthened their immune systems through drug therapy.

Solution

Passage Analysis:

Text from Passage	Analysis
A two-year study beginning in 1977 found that, among 85-year-old people, those whose immune systems were weakest were twice as likely to die within two years as others in the study.	What it says: Study found elderly people with weak immune systems died twice as often within two years What it does: Sets up the main finding that connects weak immunity to higher death rates What it is: Study finding Visualization: Out of 100 elderly people: Weak immunity group = 40 deaths, Strong immunity group = 20 deaths
The cause of their deaths, however, was more often heart disease, against which the immune system does not protect, than cancer or infections, which are attacked by the immune system.	What it says: These people mostly died from heart disease (which immunity doesn't fight) rather than cancer/infections (which immunity does fight) What it does: Creates a puzzle by showing the deaths weren't from things the immune system actually protects against What it is: Study finding that complicates the initial correlation Visualization: Deaths in weak immunity group: Heart disease = 25 people, Cancer/infections = 15 people

Argument Flow:

The passage presents a study finding and then immediately introduces a puzzling contradiction. We start with a clear correlation between weak immunity and higher death rates, but then learn that these deaths were mostly from heart disease - something the immune system doesn't even protect against.

Main Conclusion:

There's no explicit conclusion in this passage - it simply presents a medical puzzle where weak immune systems correlate with higher death rates, but the deaths aren't from causes that immunity would prevent.

Logical Structure:

This isn't a traditional argument with premises supporting a conclusion. Instead, it's a descriptive passage that sets up a paradox: if people with weak immune systems are dying more often, but not from things their immune system would protect against anyway, then what's really causing the higher death rate? The passage leaves this question unanswered, which is why we need to find an explanation in the answer choices.

Prethinking:

Question type:

Paradox - We need to explain how weak immune systems can be associated with higher death rates even when the deaths aren't from diseases that the immune system actually fights against

Precision of Claims

The claims are quantitative (twice as likely to die) and qualitative (heart disease was MORE OFTEN the cause than cancer/infections). We must respect that weak immunity group had 2x death rate but mostly died from heart disease, not immune-related diseases

Strategy

We need to find scenarios that explain why people with weak immune systems would die more often from heart disease specifically, even though immune systems don't protect against heart disease. We're looking for a common underlying factor that both weakens immunity AND increases heart disease risk simultaneously

Answer Choices Explained

There were twice as many infections among those in the study with the weakest immune systems as among those with the strongest immune systems.

This doesn't help explain the paradox at all. If anything, this makes the puzzle worse because it confirms that weak immune systems do lead to more infections, yet the passage tells us people died more from heart disease than infections. This choice actually supports what we'd expect (weak immunity → more infections) but doesn't explain why heart disease was the bigger killer.

The majority of those in the study with the strongest immune systems died from infection or cancer by 1987.

This is talking about deaths that happened after the two-year study period and focuses on people with strong immune systems. We need to explain why people with weak immune systems died more often from heart disease during the study period, so this choice is completely off-topic.

Some of the drugs that had been used to treat the symptoms of heart disease had a side effect of weakening the immune system.

This is our answer! This beautifully explains the paradox. If people were taking heart disease medications that weakened their immune systems, then those with weak immunity would likely be people who already had heart disease. Since they already had heart disease, they'd naturally be more likely to die from heart disease progression rather than from infections or cancer. The weak immune system is present but isn't the cause of death - it's just a side effect of treating the real underlying problem (heart disease).

Most of those in the study who survived beyond the two-year period had recovered from a serious infection sometime prior to 1978.

This talks about survivors and past infections, but doesn't explain why people with weak immune systems died more often from heart disease during the study. It's focused on the wrong group (survivors) and the wrong timeframe (before the study).

Those in the study who survived into the 1980s had, in 1976, strengthened their immune systems through drug therapy.

Again, this focuses on survivors and events before the study period. We need to explain deaths during the study period, not survival after it. This choice doesn't address our paradox at all.

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