A cross-sectional study conducted in a community finds a higher prevalence of diabetes among those with low physical activity compared with those who exercise regularly. The major threat to causal inference in this study design is:

• A Confounding
• B Information bias
• C Inability to establish temporal sequence ✓
• D Selection bias due to non-response

Explanation

In a cross-sectional study, exposure and outcome are measured simultaneously, so it is impossible to determine whether low physical activity preceded diabetes or whether diabetes caused reduced physical activity (reverse causality). This inability to establish temporal sequence is the fundamental causal inference limitation of cross-sectional studies. Confounding can be present but is not the major distinguishing limitation of this design. Temporal ambiguity specifically defines why cross-sectional studies can demonstrate association but not causation.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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