Which symptom is commonly associated with hypoxia?

Drowsiness is a symptom commonly associated with hypoxia, which is the condition resulting from insufficient oxygen reaching the tissues. When the body or brain does not receive enough oxygen, several physiological responses occur. One of the most evident effects on the central nervous system is altered consciousness, which can manifest as drowsiness or lethargy. This is a direct response to the brain's decreased oxygen supply, leading to impaired cognitive functions and responsiveness.

In contrast, while increased heart rate, vision changes, and nausea can occur under conditions related to hypoxia, they are not as directly linked to the state of oxygen deprivation. Increased heart rate may result from the body's effort to compensate for lower oxygen levels by pumping blood faster, but it does not reflect the mental state impairment that hypoxia induces. Vision changes can occur due to various factors but are not definitive indicators of hypoxia. Nausea can also arise due to several reasons, including anxiety or other physiological reactions, yet it does not specifically correlate to the primary effects of hypoxia on the nervous system. Thus, drowsiness serves as a more specific and commonly recognized symptom related to a lack of oxygen in the body.