Posts Tagged Risk Factor
New research shows that Alzheimer’s disease hits people in their 60s and 70s harder than people who are 80 years and older.
Researchers at the University of California, San Diego School of Medicine note that the greatest risk factor for Alzheimer’s is age. In fact, by the age of 85, the likelihood of developing the dreaded neurological disorder is roughly 50 percent, they say.
But in their study, they found that the “younger elderly” — those in their 60s and 70s — showed higher rates of cognitive decline and faster rates of tissue loss in brain regions that are vulnerable during the early stages of Alzheimer’s, according to Dominic Holland, Ph.D., a researcher in the Department of Neurosciences at UC San Diego and the study’s first author.
“Additionally cerebrospinal fluid biomarker levels indicate a greater disease burden in younger than in older individuals,” he said.
Holland and his colleagues, using imaging and biomarker data from participants in the Alzheimer’s Disease Neuroimaging Initiative, examined 723 people, ages 65 to 90 years, who were categorized as either cognitively normal, with mild cognitive impairment (an intermediate stage between normal, age-related cognitive decline and dementia) or suffering from full-blown Alzheimer’s disease (AD).
The findings have implications for diagnosing the disease — which currently afflicts an estimated 5.6 million Americans, a number expected to triple by 2050 — and efforts to find new treatments, the researchers said.
At present, there is no cure for Alzheimer’s and existing therapies do not slow or stop the disease’s progression.
A key feature in the diagnosis of Alzheimer’s is its “relentless progressive course,” Holland said.
“Patients typically show marked deterioration year after year. If older patients are not showing the same deterioration from one year to the next, doctors may be hesitant to diagnose AD, and thus these patients may not receive appropriate care, which can be very important for their quality of life.”
Holland said it’s not clear why the disease is more aggressive among the younger elderly.
“It may be that patients who show onset of dementia at an older age, and are declining slowly, have been declining at that rate for a long time,” added co-author Linda McEvoy, Ph.D., associate professor of radiology. “But because of cognitive reserve or other still-unknown factors that provide ‘resistance’ against brain damage, clinical symptoms do not manifest till later age.”
Another possibility is that older patients may be suffering from mixed dementia — a combination of Alzheimer’s and other neurological conditions, Holland said. These patients might withstand the effects of Alzheimer’s until other adverse factors, such as brain lesions caused by cerebrovascular disease, take hold. At that time, Alzheimer’s can only be definitively diagnosed by an autopsy, he said.
Clinical trials to find new treatments for the disease may be affected by the differing rates of progression, researchers said.
“Our results show that if clinical trials of candidate therapies predominately enroll older elderly, who show slower rates of change over time, the ability of a therapy to successfully slow disease progression may not be recognized, leading to failure of the clinical trial,” said Holland. “It’s critical to take into account age as a factor when enrolling subjects for AD clinical trials.”
While the obvious downside of the findings is that younger patients with Alzheimer’s lose more of their productive years, “the good news in all of this is that our results indicate those who survive into the later years before showing symptoms of AD will experience a less aggressive form of the disease,” Holland concluded.
The research appears online in the journal PLOS One.
Among individuals with psychosis who are also heavy marijuana users, the age they first used marijuana is strongly linked to the age of their first bout of psychosis, according to a study of 57 patients.
Although marijuana use by itself is neither sufficient nor needed to trigger schizophrenia, “if cannabis use precipitates the onset of psychosis, efforts should be focused on designing interventions to discourage cannabis use in vulnerable individuals,” Dr. Juan A. Galvez-Buccollini and his associates said.
This caution pertains to someone with a first-degree relative with psychosis, which is “the highest risk factor for schizophrenia,” said Dr. Lynn E. Delisi, senior investigator for the study, a psychiatrist at the Boston VA Medical Center in Brockton, Mass., and professor of psychiatry at Harvard Medical School, Boston.
If someone had a first-degree relative, “I would caution them about the consequences of cannabis use and the association with schizophrenia,” she said.
Findings from previous research has shown that marijuana use is associated with an earlier age of psychosis onset in people abusing multiple substances, but studies have not looked at a possible link between the onset of cannabis use itself and resulting psychosis.
Because of this, Dr. Galvez-Buccollini, a psychiatry researcher at VA Boston Healthcare System and Harvard, and his colleagues interviewed 57 patients with a current diagnosis of schizophrenia, schizoaffective disorder, schizophreniform disorder, or psychosis not otherwise specified, who also had a history of heavy cannabis use before the onset of psychosis. They defined heavy cannabis use as 50 or more uses during a one year period.
Average age of the subjects was 25 years with a range of 18-39 years. Of the total, 83 percent were men, and 88 percent were not married. The average age of psychosis onset was 22 years, and the average age for first psychosis-related hospitalization was 23.
Schizophrenia was the most common psychosis (42 percent), followed by schizoaffective disorder (32 percent). The average age of first marijuana use was 15, preceding psychosis onset by an average of 7 years.
During the study period, the prevalence of daily cannabis was 59 percent with another 30 percent reporting use 2-5 days per week, and the remaining 11 percent reporting weekly use. Alcohol abuse was 16 percent and alcohol dependence was 8 percent.
The researchers found a statistically significant link between the age when cannabis use first started and the age when psychosis was first diagnosed. This association was consistent after researchers excluded patients with any diagnosis of alcohol abuse or dependency during their lifetime.
The analysis also showed a strong link between the time a patient first smoked marijuana and their age of first psychosis hospitalization.
Marijuana affects dopamine receptors and can have other neurochemical effects.
“There are two components of cannabis, one that potentiates and another that antagonizes psychotic symptoms,” said Delisi. The balance between these two effects can differ among various strains of cannabis, she added.
Source: Schizophrenia Research