May 22 (HealthDay News) -- People who are obese and have type 2 diabetes often have undiagnosed sleep apnea as well, a new study has found.

In fact, of the 306 participants in the study, about 87 percent were found to have sleep apnea but had never been diagnosed with the disorder. The findings appear in the June issue of Diabetes Care.

People in the study, all obese and all with type 2 diabetes, had participated in a sleep study and answered questions about sleep apnea symptoms such as snoring and daytime sleepiness.

More than 30 percent of the study participants had 16 to 20 episodes per hour in which their breathing would stop during sleep, and 22 percent had more than 30 episodes an hour, which is considered severe sleep apnea, according to the researchers.

Most of those who were undiagnosed also had a larger waist circumference, which the researchers found to be significantly associated with sleep apnea, as is higher body-mass index (BMI).

"The high prevalence of undiagnosed and, therefore, untreated sleep apnea among obese patients with diabetes constitutes a serious public health problem," study author Gary D. Foster, director of the Center for Obesity Research and Education at Temple University, said in a school news release.

Sleep apnea increases the risk of heart disease and stroke, according to the release.

"Doctors who have obese patients with type 2 diabetes need to be aware of the possibility of sleep apnea, even if no symptoms are present, especially in cases where the patient has a high BMI or waist circumference," Foster said.

SOURCE: Temple University, news release, May 21, 2009