Daily shots of growth hormone-releasing hormone (GHRH) improved cognition in both healthy adults and those with mild cognitive impairment, researchers reported.
In a five-month randomized trial, the substance, given subcutaneously, was associated with a significant improvement in cognitive performance compared with placebo, according to Laura Baker, PhD, of the University of Washington School of Medicine in Seattle, and colleagues.
The benefit was driven by significantly better executive function and a trend toward better verbal memory, although visual memory was not changed, the group reported online in Archives of Neurology.
GHRH stimulates release of growth hormone from the pituitary, in a pulsatile fashion, which in turn causes the release of insulin-like growth factor 1 from the liver, the researchers noted.
All three “have potent effects on brain function, their levels decrease with advancing age, and they likely play a role in the pathogenesis of Alzheimer’s disease,” Baker and colleagues wrote.
Evidence suggests that elevating hormone levels in people at risk for cognitive impairment might prevent mental decline or improve function, they noted.
To test the idea, they enrolled 152 adults, ages 55 to 87, including 66 with mild cognitive impairment (MCI). They were randomly assigned to placebo or tesamorelin (Egrifta), a stabilized analog of human GHRH, self-administered daily by subcutaneous injection.
All told, 137 participants — 76 healthy volunteers and 61 people with MCI – completed the 20-week study.
The primary outcome was cognitive change measured by a battery of standard tests at baseline and weeks 10, 20, and 30 (following a 10-week washout period). The researchers also conducted blood tests at those intervals to measure circulating levels of the three hormones.
- GHRH increased insulin-like growth factor 1 levels by an average factor of 2.17, which was significant at– still within the normal physiological range.
- On an intent-to-treat analysis, including 151 of the 152 volunteers, those taking GHRH had an improvement in cognition overall that was significant at and was comparable among both healthy participants and those with MCI.
- Among the 137 who completed the study, the pattern was similar but more robust.
- Analysis showed that GHRH significantly improved executive function, appeared to improve verbal memory, but had no effect on visual memory
GHRH also reduced body fat by 7.4 percent and, among those with MCI, increased fasting insulin levels by 35 percent.
Adverse events were mostly mild but were more common among those getting GHRH — 68 percent versus 36 percent.
The authors cautioned that the generalizability of the study is limited by the small sample size.
“Larger and longer-duration treatment trials are needed,” they concluded, “to firmly establish the therapeutic potential of GHRH administration to promote brain health in normal aging and ‘pathological aging.'”
GHRH, Laura Baker
How old do you think you smell? A new study suggests that humans possess the ability to judge whether a person has reached their senior years just by sniffing their body odor.
People in the study correctly gauged whether the former wearer of an underarm pad was elderly or not just by sniffing it. And for the record, most didn’t think “old-people smell” was off-putting at all.
The finding “shows that there’s yet another signal hidden in the body odor that we are somehow able to extract and make use of,” said study co-author Johan Lundstrom, an assistant professor at the Monell Chemical Senses Center, in Philadelphia.
As for the notion that “old-people smell” doesn’t leave people as disgusted as you might expect, Lundstrom said the odor’s power — or lack thereof — appears to have a lot to do with whether the elderly are actually physically present. “Lacking a context, the negativity of the body odors disappear,” he said.
The study authors launched their research as part of an effort to better understand the chemical signals that people detect in body odor. Previous research had suggested that we can pick up signs of sickness in other people’s body odor and even get a sense of whether someone is related to us, Lundstrom said.
Animals appear to be able to detect age through body odor, he said, although it’s not clear why it might matter to them. One theory is that the signal could let other animals know that an animal is older and thus more likely to produce offspring because it’s managed to stay alive so long, he said.
In the new study, 56 people — 20 young (20 to 30 years old), 20 middle-aged (45 to 55), and 16 elderly (75 to 95) — wore clean T-shirts and underarm pads while sleeping. The pads soaked up a sample of each individual’s body odor.
The researchers then asked 41 young people to smell the resulting odors — from pads kept in glass jars — and try to tell them apart.
Participants were generally able to discriminate between the age groups, but they weren’t much better at it than chance, Lundstrom said. However, they were able to do a better job of grouping together body odors from older people and identifying them as coming from the elderly.
“The old-age body odor sticks out,” Lundstrom said, but it didn’t do so in a negative way. In fact, the subjects tended to think the old age body odors were more pleasant and less intense than those of other age groups.
One factor might explain that: Older men smell more like women, possibly because they’ve lost testosterone, Lundstrom said.
He also noted that the people who provided their body odor for the study were healthy. That means the older people did not suffer from problems that can occur among seniors that might affect their body odors, such as incontinence.
The “popular prejudice” against the odor of the elderly probably reflects people’s distaste for odors in geriatric wards and nursing homes, noted one expert, Tim Jacob, a professor of biosciences at Cardiff University, in England, who studies smell and is familiar with the new study’s findings.
“This is obviously an unfair association,” he said. “But if people know where the smell originates [that is, in an older person], they may be unconsciously or consciously prejudiced. In this study they did not know where the smell originated.”
So how might people be able to detect old age through smell? It’s not clear, Lundstrom said. One possibility is that we’re not detecting old age specifically, but instead a signal that “piggybacks” on chemical signs of disease in the elderly, he said.
In the big picture, “given the research showing the importance of the olfactory — smell — system among other animal species, it is likely that humans possess similar capabilities that we don’t yet fully understand, yet influence our behavior more than we realize,” said Elizabeth Krusemark, a smell researcher and postdoctoral fellow at the University of Wisconsin Madison’s Cognitive and Affective Neuroscience Lab.
Cardiff University, Elizabeth Krusemark, England, Tim Jacob