Which of the following is an effect of caffeine on sleep?

Caffeine is a well-known stimulant that can significantly impact the quality of sleep. When consumed, caffeine blocks the actions of adenosine, a neurotransmitter that promotes sleep and relaxation. As a result, its intake, particularly later in the day, can lead to difficulties in falling asleep, maintaining sleep, and ultimately reduces overall sleep quality. Individuals may experience more awakenings during the night, lighter sleep stages, and a decreased proportion of deep sleep, all indicative of compromised sleep quality.

In contrast, the other options suggest positive effects on sleep, which are not aligned with the well-documented effects of caffeine. For instance, caffeine does not increase total sleep time; instead, it often leads to a significant reduction in sleep duration. It also does not make it easier to fall asleep, as caffeine's stimulating properties can prolong the time taken to do so. Lastly, while one might wish for uninterrupted sleep to be promoted by caffeine, the reality is that its consumption typically disrupts sleep continuity and increases wakefulness during the night. Thus, the impact of caffeine is clearly negative in the context of sleep quality, making the correct choice C.