People with Type 2 diabetes may be at increased risk for developing dementia as they age, several studies have suggested. Now researchers say the higher odds may be linked to life-threatening drops in blood sugar, or hypoglycemia, usually caused by excess insulin.

A long-term study of thousands of older patients with Type 2 diabetes in Northern California found that those who had experienced even one episode of hypoglycemia serious enough to send them to a hospital were at higher risk for developing dementia than diabetic patients who had not experienced such an episode. With each additional episode, the risk of developing dementia increased, the study found.

The findings, to be published on Wednesday in the Journal of the American Medical Association, are significant given the high rates of Type 2 diabetes around the world, and the expectation that dementia rates will increase as the population ages.

“We’ve known for some time that patients with Type 2 diabetes are at greater risk of dementia and cognitive problems,” said Rachel A. Whitmer of the Division of Research at Kaiser Permanente in Oakland, Calif., one of the authors. “This adds to the evidence that balance of glycemic control is important, and that trying to aim for a very low glycemic target might not be beneficial and might even be harmful.”

The study found that the risk of dementia among patients who had experienced a single episode of hypoglycemia that required hospitalization was 26 percent higher than the risk for patients who had never had an episode.

Patients who had experienced two episodes faced an increased risk of 80 percent, while those who had experienced three episodes or more had a 94 percent increase in risk, or almost double the odds of developing dementia.

“To see an effect after just one episode is remarkable,” said Dr. Alan M. Jacobson, a researcher at the Joslin Diabetes Center in Boston. An earlier study of Type 1 diabetes and dementia found no connection, Dr. Jacobson noted.

Researchers gathered their data from 16,667 Kaiser Permanente patients with Type 2 diabetes. They used hospital data to determine how many had experienced severe hypoglycemic episodes from 1980 to 2002 and how many had first received a diagnosis of dementia from 2003 to 2007, when their mean age was 74 to 78.

LONDON (Reuters) – Rigorous workouts lasting as little as three minutes may help prevent diabetes by helping control blood sugar, British researchers said on Wednesday.

The findings published in the journal BioMed Central Endocrine Disorders suggest that people unable to meet government guidelines calling for moderate to vigorous exercise several hours per week can still benefit from exercise.

“This is such a brief amount of exercise you can do it without breaking a sweat,” said James Timmons, an exercise biologist at Heriot-Watt University in Edinburgh, who led the study.

“You can make just as big as an effect doing this as you can by doing hours and hours of endurance training each week.”

Type 2 diabetes, which affects an estimated 246 million adults worldwide and accounts for 6 percent of all global deaths, is a condition in which the body gradually loses the ability to use insulin properly to convert food to energy.

Very strict diet and vigorous, regular and sustained exercise can reverse type 2 diabetes, but this can be difficult for many people. The condition is closely linked to inactivity.

Timmons and his team showed that just seven minutes of exercise each week helped a group of 16 men in their early twenties control their insulin.

The volunteers, who were relatively out of shape but otherwise healthy, rode an exercise bike four times daily in 30 second spurts two days a week.

After two weeks, the young men had a 23 percent improvement in how effectively their body used insulin to clear glucose, or blood sugar, from the blood stream, Timmons said.

The effect appears to last up to 10 days after the last round of exercise, he added in a telephone interview.

“The simple idea is if you are doing tense muscle contractions during sprints or exercise on a bike you really enhance insulin’s ability to clear glucose out of the bloodstream,” Timmons said.

The findings highlight a way for people who do not have time to work out a few hours each week as recommended to improve their health, he added.

His team did not look for other important benefits to health that come from exercise, such as lowered blood pressure or weight control, but said another study had shown similar benefits to heart function.

But Timmons said getting people to exercise even a little could translate into big savings for health systems that spend hundreds of million of dollars treating diabetes.