Some of the major symptoms associated with Alzheimer’s disease tend to appear earlier in Hispanic Americans than in non-Hispanic whites, and also regularly become more severe in this particular ethnic group, according to a new study.

Alzheimer’s is an age-related illness that is at least partially caused by the build-up of plaques made of amyloid-beta proteins in the brain. Symptoms of the disease are generally categorized as being either cognitive – such as memory loss or disorientation – or neuropsychiatric, such as depression, delusions, anxiety, hallucinations, and apathy.

To conduct the study – which appears in the Journal of Neuropsychiatry and Clinical Neuroscience – the researchers recruited 975 Alzheimer’s sufferers, along with 875 non-sufferers and 339 people with mild cognitive impairment, which often precedes the development of Alzheimer’s. All participants were from Texas, and were predominantly Mexican-Americans and non-Hispanic whites.

Using the Neuropsychiatric Inventory Questionnaire (NPI-Q) to assess the severity of 12 neuropsychiatric symptoms in each participant, the study authors found that Mexican-Americans suffering from Alzheimer’s tended to have greater scores for 11 of these symptoms than non-Hispanics.

“Our study shows that the severity and proportion of neuropsychiatric symptoms is significantly higher in a Hispanic group compared to non-Hispanic whites,” explained study co-author Ricardo Salazar in a statement.

In particular, depression, anxiety, irritability, hallucinations, and elation were significantly more common in Hispanics than non-Hispanics with the disease. Among those with mild cognitive impairment, however, no difference was found in the severity of symptoms between the two groups.

Results also showed depression and anxiety are more common in Hispanics at age 50 than non-Hispanics. This, say the researchers, may provide firm evidence that the appearance of these symptoms precedes the development of Alzheimer’s.

Offering an explanation for these findings, Salazar proposes that the disease may occur via a unique pathway in Hispanics. “When patients have neuropsychiatric symptoms, that signifies deterioration of different areas of the brain,” he said. As such, he believes amyloid beta plaques may occur in specific brain areas in Hispanics, although more research will be needed to corroborate this.