The phrase "are less alert to" is correct and usable in written English.
It can be used to describe a state of reduced awareness or attentiveness to something.
Example: "In a noisy environment, people are less alert to subtle sounds that might indicate danger."
Alternatives: "are less aware of" or "are not as attentive to".
The chief rabbi of the Bukharans, Itzhak Yehoshua, said that back home, amid a creaky Soviet legal system and traditional Muslim neighbors, Bukharan society was "less alert" to women's rights.
In their study of stress in working women, Haque & Haleem indicated that working women had higher stress levels and lower serotonin levels [ 16], and because serotonin is linked to sustained attention [ 17], working mothers with low levels of serotonin could be less alert to fetal movements.
Results show that fatigued drivers faced greater attention demand, were less alert, and tended to overestimate the distance to roadside traffic signs.
This conforms to the findings of Hansen [ 21]; in a study of 60 high school seniors, students in early morning classes reported being wearier, being less alert and having to expend greater effort.
In between these hours the mind is less alert and more prone to distraction... keep reading.
The home side were less dynamic after the break, and tiring legs and minds turned out to be less alert.
This demotion manifests itself in Baker's language, which is less alert and less frisky than we've come to expect from him.
Likewise, if that same organism is less alert when the first stimulus occurs, it is likely to be much less responsive initially, but rapidly sensitizes, i.e., increases its responsiveness to the next stimulus, (hypothetically, in order to receive more information) and, if the stimulus is then assessed to be insignificant, habituation follows.
The next morning, they were less alert.
The creature is human, and on some days his mind is less alert than on others.
