Complex sentence: Drinking four or more cups of coffee per day does not affect the risk of hypertension compared to drinking little or no coffee; however, drinking 1--3 cups per day may be at a slightly increased risk.
Split into simpler sentences: Drinking four or more cups of coffee per day does not affect the risk of hypertension compared to drinking little or no coffee. However those who drink 1--3 cups per day may be at a slightly increased risk.