Loss of Smell is a Precursor to Cognitive Impairment in Gulf War Veterans

After the 1991 Gulf War, many veterans came home reporting a variety of medically unexplained symptoms that were initially called Gulf War Syndrome, but has come to be known today as Gulf War illness (GWI) or Chronic Multisymptom Illness (CMI). To this day, there is no widely agreed upon cause, though it is suspected to be linked to deployment-related chemical exposures such as pesticides, chemical warfare agents, and anti-nerve pretreatment used to protect troops. GWI symptoms are characterized by fatigue, pain, and cognitive dysfunction, and there has been suggestive evidence that deployed GW veterans may be at increased risk for mild cognitive impairment and dementia.

Linda Chao PhD professor at UCSF Radiology departmentAlthough anosmia – full or partial loss of the sense of smell – is not one of the more common symptoms of GWI, it is noteworthy that many veterans describe losing their sense of smell in anecdotal reports. Because anosmia is recognized as a potential early symptom of diseases like Parkinson’s and Alzheimer’s disease, Linda Chao, PhD, of the UCSF Department of Radiology and Biomedical Imaging, has sought to identify if anosmia in GW veterans could be predictive of impaired cognitive function.

Olfactory and cognitive decrements in 1991 Gulf War veterans with gulf war illness/chronic multisymptom illness,” published in Environmental Health, found evidence of olfactory and cognitive deficits and a significant correlation between the smell identification tests and cognitive assessment scores in a cohort of 80 deployed GW veterans, both male and female. Based on the findings, the study recommends that Gulf War veterans, especially those with GWI, be screened for olfactory dysfunction using simple smell identification tests. Early detection of smell loss could help with monitoring veterans for potential cognitive decline and allow for earlier intervention if needed.

Dr. Chao said, “I've been doing research with GW veterans for nearly 20 years. During that time, a few have commented to me in passing that they lost their sense of smell shortly after the war.  Other GWI researchers confirmed that they've also noticed that GW veterans do not have good senses of smell.”

Prior research has suggested the link between impaired olfaction and a higher risk of developing neurodegenerative conditions like Alzheimer's disease and Parkinson's disease in the future. Earlier studies have shown that damage in these diseases often starts in the olfactory bulb, the brain region involved in smell. While most people are inaccurate at assessing the nature and degree of their chemosensory problems, and veterans with GWI and with greater cognitive decline tend to have less accurate self-awareness, regular smell test screenings have the benefit of being easy and cost-effective to administer in routine appointments.

These findings highlight the importance of including routine smell test screening in monitoring the health of Gulf War veterans. Hypo- and anosmic veterans can then be followed longitudinally and offered targeted neuroprotective therapies as they become available.

Chao advises, “I really do believe that it may be worthwhile for the VA to screen and monitor GW veterans with these simple scratch-and-sniff tests.”