Older people with type 1 diabetes who have been to the hospital at some point for both low and high blood sugar levels may be at six times greater risk for developing dementia later, according to a new study from UC Davis Health.
The researchers also found that people with type 1 diabetes who visit the hospital for just one of the blood sugar extremes — either high or low — may also be at greater risk for developing dementia.
“People with type 1 diabetes are living longer than before, which may place them at risk of conditions such as dementia. If we can potentially decrease their risk of dementia by controlling their blood sugar levels, that could have beneficial effects for individuals and public health overall,” said study author Rachel A. Whitmer, professor and chief of the Division of Epidemiology in the Department of Public Health Sciences in the UC Davis School of Medicine.
The research is published in the June 2, 2021, online issue of Neurology.
Impact of severe glycemic events on brain health
Type 1 diabetes is a chronic condition in which the pancreas produces little or no insulin. Hypoglycemia is low blood glucose, or the main sugar in blood, that may result in loss of consciousness. Hyperglycemia results from insulin deficiency or extremely high blood sugar and dehydration. This study looked at severe glycemic events, which were defined as episodes of high or low blood sugar that resulted in an emergency room visit or hospital stay.
The study looked at 2,821 people with an average age of 56 who had type 1 diabetes. Of those, 398, or 14%, had a history of severe low blood sugar; 335, or 12%, had a history of severe high blood sugar and 87, or 3%, had both. Researchers followed up with the people for an average of seven years to determine who had been diagnosed with dementia.
— Rachel A Whitmer
Researchers found that 153 people, or about 5%, developed dementia. After adjusting for age, sex and ethnicity, the people with low blood sugar events had a 75% greater risk of developing dementia than those without one. People with high blood sugar events had more than twice the risk of developing dementia than those without one.
However, the people who experienced both types of events had more than six times the risk of developing dementia than people who had neither event.
“Our findings suggest that exposure to severe glycemic events may have long-term consequences on brain health and should be considered additional motivation for people with diabetes to avoid severe glycemic events throughout their lifetime,” Whitmer said.
A limitation of the study is that people had to be diagnosed with dementia by a health care provider to be counted as having dementia. Since many dementia cases go undiagnosed, this may have resulted in underreporting the number of cases. Whitmer noted that the study was not designed to determine whether high and low blood sugar events cause dementia. It only shows an association.
Researchers also looked at incidence rates. After adjusting for age, the incidence rate of dementia in people with low blood sugar events was 26.5 cases for every 1,000 person-years compared to 13.2 for people without. Person-years take into account the number of people in a study as well as the amount of time spent in the study. The incidence rate of dementia in people with high blood sugar events was 79.6 cases for every 1,000 person-years, compared to 13.4 for people without.
For people who had both high and low blood sugar events at various times, the incidence rate of dementia was 98.5 for every 1,000 person-years, compared to 12.8 for those who had neither.
A version of this press release was published by the American Academy of Neurology. Additional authors on this study are: Paola Gilsanz, Andrew J. Karter and Charles P. Quesenberry, Kaiser Permanente Division of Research; and Mary E. Lacy, Department of Epidemiology and Biostatistics, UC San Francisco.