What factor can decrease night visual acuity due to the sensitivity of rods?

Cabin altitude can significantly decrease night visual acuity because it affects the amount of available oxygen in the environment, which in turn impacts the function of rods in the retina. Rods are the photoreceptor cells responsible for vision in low-light conditions; they are highly sensitive to light but require a high oxygen level to function optimally.

When flying at high altitudes, the reduced atmospheric pressure leads to lower partial pressures of oxygen, commonly resulting in hypoxia, or a deficiency in the amount of oxygen reaching the body's tissues. This can impair the ability of the rods to perform effectively, leading to decreased sensitivity and poorer night vision. Additionally, under such conditions, adaptation to low light can be hindered, making it more challenging to detect objects or movements in low-light situations.

The other choices—cabin humidity, external sunlight, and ambient noise—do not have a direct effect on the sensitivity of the rods in the same way. While they could influence overall comfort or environmental conditions, they do not impact the fundamental biological processes related to how visual acuity is maintained in low-light conditions.