The phrase “more ill than” is correct and usable in written English.
You can use it when comparing two levels of illness, as in the following example: “Her cold had become more ill than it was just a day before.”.
Five participants reported that they did not see themselves as mentally ill, or did not identify with others with mental illness and held the view that others with mental illness are more "ill" than they were.
Fourth, scores of severity of illness and laboratory values may suggest that patients with incomplete recall were more ill than those with complete recall.
The effect was more ill than good.
Now, I see that she must already have been feeling much more ill than anyone realised.
We hear lots of reports from A&E departments of older people particularly turning up more ill than they have in the past".
Hospital patients are often far more ill than those I saw only a decade ago, and they stay for shorter periods.
They both run a cash-rich sport that defies current economic problems, yet at times they imagine they can tackle more ills than the United Nations.
"Why cause more ill will than necessary?" More than a dozen friends responded to Mr. Thomas's message.
"Women are more likely than men to be disabled by chronic illnesses," Wendell writes, "and women (including women with other disabilities) suffer more ill health than men.
Women from rural and traditional backgrounds reported more ill health than middle class women.
Evidence from developing and developed countries suggests that women tend to report more ill health than men.
