Complications from diabetes, which affects more than 2 million Californians, account for one-fifth of the cost of preventable hospitalizations.
And the obesity-related disease is on the rise, increasing by almost 15 percent from 2000 to 2004 and taking a greater toll on older people in Sonoma County and across the state, according to a report by California's Office of Statewide Health Planning and Development.
Amputation of a foot or leg due to diabetes costs $20,000, the single most expensive preventable condition, the state report said.
The cost of diabetes is a key part of the estimated $3.5 billion a year in California hospital expenses that experts say could be prevented or reduced if more people had health insurance and if they took better care of themselves.
Reducing preventable admissions by just 3 percent a year for the next 10 years could save more than $1 billion, according to the report. Improving access to regular medical care will help keep people out of hospitals, public health officials say. But individual responsibility plays a role, too.
"Patients have to do their part," said Suzanne Drake, wound care manager at Santa Rosa Memorial Hospital.
Diabetics need to quit smoking, stop drinking alcohol, modify their diet and lose weight, Drake said. For those who don't, medical care can only do so much.
"One of our biggest problems is getting compliance on the patient side," she said.
In Sonoma County, the rate of preventable hospital admissions for diabetes - including amputation of legs and feet - ranks slightly above the state average, the report said.
The difference is not significant, but the report is an assessment of "how well our health system is working," said Dr. Mary Maddux-Gonzalez, county public health officer.
"There are real disparities in access to primary care in our community and throughout the country," she said. "We have to diagnose people early so they can get the care they need."
The county's rate of preventable hospitalizations is below the state average for 12 of the 15 chronic conditions and acute illnesses covered by the state report.
Asthma, pneumonia, high blood pressure, congestive heart failure, lung disease and ruptured appendix are among the other causes of preventable hospitalizations, the report said.
Four of the chronic conditions relate to diabetes, with 1.6 million new cases diagnosed each year in young and old Americans. It is the nation's sixth-leading cause of death, and along with Alzheimer's disease, has the fastest-growing death rate.
Type 1 diabetes, which is diagnosed in children and young adults, accounts for 5 to 10 percent cases of the disease. It is treated with insulin therapy.
Type 2, previously known as adult-onset diabetes, typically requires diet and exercise adjustments to control blood sugar level.
Foot and leg amputations result from a minor wound that festers in a diabetic's foot numbed to pain by neurological damage from the disease.
In 2008, there were 120 lower-limb amputations due to diabetes in Sonoma County, the county Department of Health Services said.
The state report said Sonoma had 29.7 diabetes-related amputations per 100,000 persons in 2008, compared with a statewide rate of 27.6.
Improving access to regular medical care is the key to reducing many of the cases of preventable hospitalizations, said Michael Kassis, a research analyst with the health planning office.
"That's No. 1," he said. "You've got to have some way to access the health care system."
Overall, the report is "generally good news," with a drop in statewide hospitalization rates for 10 conditions between 1999 and 2008. The rate for three conditions has increased and for one it is unchanged.
But the rates for individual ZIP codes, which the state soon will report to county health officers, will pinpoint the real problems, Kassis said.
"Not everyone is getting the same level of preventive care," Kassis said, even in counties and regions where the hospitalization rates are dropping.
"Our goal should be zero hospitalizations for chronic conditions," Maddux-Gonzalez said.
Preventable hospitalizations have been dropping an average of 3 percent a year for the past 10 years, and Kassis said it is "reasonable" to expect a continued decline at that rate - with a potential $1 billion savings.
The $3.5 billion cost of preventable hospitalizations in 2008 accounted for 6 percent of total hospital costs, the state report said.
That doesn't count lost worker productivity, nor the hardships for patients and their families due to preventable hospital stays, Kassis said.
It adds up to an argument for the health care overhaul law, which aims to provide insurance for about 30 million more Americans - including an estimated 40,000 in Sonoma County - by 2014.
"You begin to understand why it's important to get people insured," he said. "You can't beat the facts."
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