"troubling increase" is a correct and usable phrase in written English.
You can use it to refer to a rise in something that is concerning. For example: "There has been a troubling increase in the number of people who are out of work."
That has real implications: There's a continuing and troubling increase in the spread of STDs, especially among younger people.
A troubling increase in prison suicides suggests that all of the problems have not been solved.
The N.S.A. programs represent a troubling increase in state power, even if — so far, and so far as we know — they have not occasioned a troubling increase in state wrongdoing.
The greater access to fairer jobs and pay for women but a troubling increase in inequality between less educated and more educated workers".
The blink response to this case is only the latest example of a troubling increase in the speed of our reactions.
That has led to a complacency that helps explain a troubling increase in new H.I.V. infections among young men who have sex with men.
While the sheer number of infections is troubling, increases in gonorrhea are particularly concerning, because we may soon be running out of antibiotics to treat this infection.
Problems arising from anesthesia are rare, but researchers at Duke University Medical Center have concluded that troubles increase significantly in operations that begin late in the afternoon.
As his troubles increase, Wasicsko's eyes become wells of need: he's diligent, canny, a good listener, but he's hooked on adoration.
All the while the housing market still hasn't managed to recover, mortgage troubles increase, and Americans are finding it more difficult to pay their loans.
But as his troubles increased, so did his fame and his album sales.
