The study appears in the Archives of Internal Medicine. The researchers included Kristen Knutson, PhD, of the University of Chicago's medicine department.
Knutson commented on the findings in a University of Chicago Medical Center News release.
"Although we can't be certain whether sleep loss makes diabetes worse or the diabetes interferes with sleep, it only makes sense for everyone, but especially patients with diabetes, to give themselves the opportunity to get enough sleep," Knutson says.
Sleep and Blood Sugar
Previous studies have shown that people without diabetes may be more likely to get diabetes or have problems controlling their blood sugar if they get insufficient or poor-quality sleep.
Participants answered questions about their weeknight sleep habits.
They reported how much sleep they got and how much sleep they thought they needed. They also rated the quality of their sleep.
Poor Sleep Common
Average weeknight sleep reported was six hours; that's on the skimpy side.
"Only 6% of patients reported obtaining at least eight hours of sleep on weeknights and only 22% obtained at least seven hours," the researchers write.
Sleep quality generally wasn't good, either. About seven in 10 participants were classified as having poor-quality sleep.
Hemoglobin A1c levels were worse in participants who said they got too little sleep and other participants who reported poor-quality sleep.
Those results held after screening out 39 people who said pain frequently disturbed their sleep.
Depression Depression, which can skew sleep habits, didn't affect the results, based on depression questionnaires that the patients completed.
Sleep Debt, Sleep Quality
The researchers split patients into those with and without diabetes complications.
Among those without diabetes complications, hemoglobin A1c levels were tied to "sleep debt," the shortfall between how much they slept and how much sleep they thought they needed.
But in patients with diabetes complications, sleep quality was more strongly tied to hemoglobin A1c levels than reported sleep debt.
The bottom line: The amount of sleep and the quality of sleep both mattered, with some differences in patients with and without diabetes complications.
Future studies should test whether improving sleep length and quality improves blood sugar control in people with type 2 diabetes, write Knutson and colleagues.
They note that sleep loss has become increasingly common in modern society "and it cannot be excluded that this behavior has contributed to the current epidemic of type 2 diabetes."