Close to death, a 14-year-old boy lay in a Toronto hospital bed with type-1 diabetes. He was no ordinary teenager however, because he became the first person in the world to receive an insulin injection. That was in 1922. He survived, as have countless others since, thanks to this medical marvel.

Although only associated with diabetes, insulin has in fact many other potential uses in wound healing, heart attacks, cancer, and more. A recent study suggests it could play a key role in preventing Alzheimer’s.

Insulin is vital for healthy brain function. It enters many key brain regions to protect neurons and support higher cognitive processes including attention, learning and memory.

With aging, insulin sensitivity and signaling can become impaired, but in a diabetic of any age it’s greatly exacerbated. In such a patient brain aging is accelerated, and the risk of Alzheimer’s is increased considerably.

The latest research shows that supplementing insulin via an intranasal spray can improve verbal memory and cognitive impairment, so scientists from Harvard Medical School set up a trial to test the long-term effects of using the spray in middle-aged and older folks with and without diabetes.

Walking Speed Predicts Cognitive Decline 

For the randomized, double-blind trial, researchers enrolled 223 men and women aged 50 to 85. Of these, 51 had type-2 diabetes (T2D) and took intranasal insulin (INI) once a day via an electronic atomizer for 24 weeks. Meanwhile, another 55 with T2D took an intranasal placebo containing saline. The rest were either non-diabetics or had pre-diabetes. Of these, 58 were given INI and 59 took the saline solution.

They assessed the patient groups at the end of the treatment and again after a 24 week follow up period. Before the trial began each had a battery of tests to assess attention, memory, and executive function. A subset of volunteers also underwent brain scans.

INI had never been tested to measure its effect on walking speed, which is an important indicator of overall health. Slower walking speed correlates with reduced brain blood flow in diabetics and can predict cognitive impairment. The new trial therefore included this.

Normal walking speed was measured over six minutes, and dual task walking speed was assessed by asking participants to walk while counting backwards, subtracting in sevens.

At the pre-treatment stage, diabetic patients were found to walk slower and had worse cognition than those without the condition, supporting previous findings.

Would they be helped by the insulin spray?

Improves Memory and Walking Speed 

At the end of 24 and 48 weeks, those with T2D taking INI had faster walking speeds than diabetics taking placebo. Brain scans also showed an increase in blood flow in the frontal lobe and lower plasma insulin and insulin resistance compared to placebo.

Those without diabetes taking INI showed improved decision-making, verbal learning, and memory. All INI treated participants combined demonstrated faster walking speed and better executive function and memory.

Participants with pre-diabetes taking INI had the most marked improvements in decision making and verbal memory.

Importantly, only mild side effects occurred among some of the trial subjects.

Senior author Dr. Long Ngo said, “The consistency of the trends in the data showing better performance on walking speed and cognition for INI-treated participants, especially in those with pre-diabetes, carries great implication for potential early intervention using INI in this population to prevent or slow down the progression toward Alzheimer Disease-related dementias.

“With 96 million adult Americans, and increasing number of younger people having pre-diabetes, this finding on the beneficial effect of INI deserves more attention and definitive confirmation in a larger trial.”


  1. https://www.bidmc.org/about-bidmc/news/2022/04/clinical-trial-shows-insulin-spray-
    improved-gait-and-cognitive-function-in-patients
  2. https://link.springer.com/article/10.1007/s00415-022-11119-6 

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