- Researchers report that using intranasal insulin may improve cognitive functions in some people with dementia-related conditions.
- They said the insulin treatment appears to have the most benefits for people with Alzheimer’s disease and mild cognitive impairment.
- Other medical experts, however, said they felt the study was flawed and aren’t ready to recommend insulin as a treatment for these conditions.
Intranasal insulin could produce some positive cognitive benefits, especially for people with Alzheimer’s disease and mild cognitive impairment, according to a
Researchers completed a review and meta-analysis of 29 studies with 1,726 participants examining intranasal insulin and cognitive function. The studies were published between 2001 and 2021.
The median dose of insulin was 40IU. Ten studies examined the effects of a single dose. The others studied several doses over a longer time, with a median duration of eight weeks. The mean age of the participants was about 53 years.
The researchers divided the participants into four categories of disorders:
- Mental health disorders, such as schizophrenia, bipolar disorders, major depressive disorder
- Alzheimer’s disease and mild cognitive impairment
- Metabolic disorders, such as diabetes
- Other disorders
Healthy, cognitively unimpaired individuals were also pooled.
The researchers reported that they did not find a significant difference in cognitive function after doses of intranasal insulin in people with mental health disorders, metabolic disorders, and other disorders.
The scientists said they found significant improvement in participants with Alzheimer’s disease and mild cognitive impairment.
“Patients with Alzheimer’s could have impaired glucose processing in the hippocampus (an area of the brain involved in human learning and memory),” Dr. Gayatri Devi, a neurologist at Northwell Lenox Hill Hospital in New York who was not involved in the study, told Medical News Today. “Intranasal insulin may help with this and improve cognition.”
One theory on why insulin can help improve memory and cognition is that memory centers in the brain are either faulty or cannot process sugar.
“It could be possible that the number of insulin receptors in the memory centers in the brain becomes faulty or are somehow deficient to process sugar, said Dr. Shae Datta, the co-director of NYU Langone’s Concussion Center and director of cognitive neurology at NYU Langone Hospital-Long Island.
“Replacing insulin helps brain metabolism. Leading to the theory that brain insulin resistance can lead to cognitive deficits,” Datta, who was not involved in the study, told Medical News Today.
The side effects of intranasal insulin include:
- Hypoglycemia, which could lead to heart attacks and stroke
- Nasal irritation or rhinitis
- Lightheadedness
- Dizziness
- Nausea
- Nose bleeds
The researchers concluded that intranasal insulin can be safely tolerated and has the potential to improve memory by directly reaching brain regions involved with the regulation of cognition.
The researchers did indicate that more research is needed to understand treatment response.
Not all medical professionals are impressed with the research.
“Overall, I was not impressed with the study,” said Dr Clifford Segil, DO, a neurologist at Providence Saint John’s Health Center in California who was not involved in the research. “Intranasal insulin has been tried for diabetes – and it failed.”
“I find it scary to give insulin to someone without an indication of diabetes. There is a risk of hypoglycemia when you give insulin to someone who does not have diabetes,” he told Medical News Today. “This can increase their risk of heart attack or stroke.”
“I agree that it is good to repurpose drugs as it can improve choices for treatment,” Segil added. “But, this study does not support repurposing this drug for memory loss. I never used it in my practice.”
“This is a meta-analysis, so a statistical compilation of multiple studies, most of them quite small,” Devi said. “This is never as good a large double-blind placebo-controlled study as that would be important in making patient-related decisions. However, every patient needs to be treated individually and decisions regarding treatment protocols must also be tailored to the individual patient.”
“A large placebo-controlled study of intranasal insulin in the treatment of patience with biomarker-confirmed Alzheimer’s disease is still needed,” Devi added. “Part of the problem with older clinical trials of Alzheimer’s was that up to a third of patients who were diagnosed clinically with Alzheimer’s did not have it on pathology.”
Datta agrees that further study is needed.
“I think we need larger human clinical trials assessing positive improvement and lack of long-term side effects prior to use. I would like differentiating information about baseline cognitive status and groups compared to each other with varying doses to see if there is a benefit,” she said.