A new analysis presented in the United States suggests that routine blood tests could play a greater role in tracking Alzheimer’s disease, particularly among people living with obesity. The research, conducted by scientists at Washington University School of Medicine in St. Louis, indicates that obesity may accelerate the early biological changes associated with the condition.

The study, which will be shared at the annual meeting of the Radiological Society of North America, examined 407 adults over a five-year period. Participants underwent regular blood tests and PET scans, the latter measuring the buildup of amyloid plaques in the brain — a hallmark of Alzheimer’s disease. The blood tests assessed proteins and other biomarkers that are linked to cognitive decline.

Dr. Cyrus Raji, associate professor of radiology and neurology and one of the study’s authors, said this research marks the first time a clear relationship has been identified between obesity and Alzheimer’s progression using blood biomarker tests. He noted that blood results were able to detect obesity’s influence on Alzheimer’s-related changes more precisely than PET scans alone.

“The fact that we can track the predictive influence of obesity on rising blood biomarkers more sensitively than PET is what astonished me in this study,” Raji said.

According to the findings, people with obesity showed faster deterioration in several key biomarkers. The researchers reported a 24 per cent faster increase in the protein plasma NfL, which is associated with nerve damage. Levels of the blood biomarker plasma pTau217 rose 29 to 95 per cent faster in individuals with obesity, and amyloid plaque accumulation increased by 3.7 per cent.

Raji said these results may give doctors new ways to monitor how Alzheimer’s develops, especially as new treatments targeting amyloid buildup become more common. By using both blood tests and imaging, doctors may be able to gain a clearer picture of how the disease responds to medication.

“It’s marvellous that we have these blood biomarkers to track the molecular pathology of Alzheimer’s disease, and MRI scans to track additional evidence of brain degeneration and response to various treatments,” he noted.

Obesity has long been recognised as a risk factor for dementia. Individuals with obesity are more likely to experience conditions such as high blood pressure, type 2 diabetes, and reduced physical activity, all of which heighten the risk of cognitive decline.

Globally, around 57 million people are living with dementia, according to the World Health Organization. Alzheimer’s disease represents the largest share, accounting for between 60 and 70 per cent of all cases.

Researchers at the University of Birmingham are preparing the first National Health Service (NHS) trial to test whether nitrous oxide, commonly known as “laughing gas,” can be safely and effectively used to treat severe or treatment-resistant depression. The move follows a major analysis combining the strongest clinical evidence to date on the gas’s potential antidepressant effects.

The study, published in eBioMedicine, examined how medically administered nitrous oxide (N₂O) affects adults with major depressive disorder (MDD) and treatment-resistant depression (TRD). TRD is typically diagnosed when patients fail to respond to at least two standard antidepressants, a situation affecting almost half of UK patients, earlier research indicates.

The analysis found that a single session inhaling 50 percent nitrous oxide produced significant reductions in depressive symptoms within 24 hours. These effects, however, were often short-lived, generally fading within a week. Repeated sessions appeared to provide more lasting improvements, echoing findings from studies on ketamine, another fast-acting treatment thought to influence similar glutamate pathways in the brain.

“Depression is a debilitating illness, made even more challenging by the fact that standard antidepressants do not provide meaningful relief for nearly half of patients,” said Kiranpreet Gill, PhD researcher at the University of Birmingham and lead author of the report. “This study consolidates the best available evidence suggesting that nitrous oxide can offer rapid and clinically significant short-term relief for patients with severe depression.”

While side effects such as nausea, dizziness, and headaches were relatively common, they were generally brief and no immediate safety concerns were identified. Researchers caution that the long-term effects of repeated nitrous oxide use remain largely unknown, and the limited number of trials makes it difficult to draw firm conclusions at this stage.

The work is part of the NIHR-funded Mental Health Mission Midlands Translational Centre, which aims to improve care for patients with severe and treatment-resistant depression. The upcoming NHS trial will assess whether nitrous oxide can be delivered safely and acceptably in clinical settings, potentially adding a new option to the growing field of rapid-acting depression treatments.

Gill added that larger trials will be necessary to determine safe, repeatable dosing strategies and to evaluate the long-term outcomes for patients. If successful, nitrous oxide could become an important addition to current therapeutic options, offering fast relief for those who do not benefit from conventional antidepressants.