What is the effect of smoking on BP readings taken before measurement?

• A. Smoking acutely elevates BP; wait at least 30 minutes after smoking before measurement.
• B. Smoking has no effect on BP readings.
• C. Smoking causes a persistent high BP.
• D. Smoking only affects BP if caffeine is also consumed.

Answer: (A)

Smoking causes a transient rise in blood pressure because nicotine triggers the sympathetic nervous system, releasing adrenaline and noradrenaline. This leads to vasoconstriction and a faster heart rate, so a BP reading taken soon after smoking can be higher than the person's usual resting level.

To avoid this measurement error, it’s recommended to wait about 30 minutes after smoking before taking a BP reading, so the acute effects wear off and the result reflects a resting BP.

This is not a permanent increase in baseline blood pressure, and while caffeine can also affect BP temporarily, the important point here is the immediate, short-lived rise caused by smoking itself.