Published on: December 20, 2012
by Crystal Phend for MedPage Today:
Alzheimer’s disease patients with adult child or other non-spouse caregivers appear to be underrepresented in clinical trials, which may influence results, researchers found.
Across six cooperative group trials, 67% of participants had spouses as their study partner compared with 26% enrolled with their adult child and 7% with a different relationship to their caregiver, Joshua D. Grill, PhD, of the Center for Alzheimer’s Disease Research at UCLA, and colleagues reported.
By comparison, national figures suggest the opposite proportions, with 68% of Alzheimer’s caregivers being adult children, children-in-law, or grandchildren.
“We observed several relevant differences that could affect trial conduct, results, and interpretations,” the group wrote online inNeurology.
The secondary analysis included 2,041 patients with mild-to-moderate disease in six Alzheimer’s Disease Cooperative Study trials with similar designs testing two different nonsteroidal anti-inflammatory drugs, B vitamin supplementation, valproate (Depakote), the omega-3 fatty acid docosahexaenoic acid, simvastatin (Zocor), and the Chinese herb huperzine.
Each required a study partner to be enrolled with the patient, typically the primary caregiver. Their relationships to the patient were similar across the trials, ranging from 62% to 68% spouses, 20% to 32% adult children, and 6% to 8% other.
While the study didn’t explain why non-spouse caregivers were underrepresented, it did point to some important factors.
Fewer adult child and “other” study partners lived with the affected patient than did the spouses. They were also less often retired than were spouse study partners (20% and 44%, respectively, versus 71%).
“This difference suggests that patients with Alzheimer’s disease who have adult child caregivers face increased logistical challenges to research participation,” Grill’s group wrote.
Patients enrolled with an adult child were also older than those with either other type of study partner. Adult child or other study partners were more likely to be with male patients.
It’s possible that non-spouse caregivers have more negative attitudes that reduce likelihood of trial participation, the researchers pointed out.
“Another possible reason is that trials typically require patients with mild severity and thus enroll young AD patients who, in turn, may be more likely to have spouses,” they added.
While Hispanic patients were underrepresented overall at just 5% of participants, they disproportionately had adult children as their study partner.
The same was true for African Americans, who represented 6% of all participants.
Patients enrolled with their adult child were twice as likely to be Hispanic and nearly three times as likely to be African American as those with spouse study partners.
“Thus, increasing enrollment of patients with Alzheimer’s disease who have adult child caregivers may facilitate increased minority participation,” the investigators noted.
Strategies to do so may be inclusion criteria such as no, or high, upper age limit and lower Mini-Mental State Examination exclusion criteria.
However, that could create challenges for trials, the group acknowledged.
Dropout rates were higher with with adult child or “other” partners (32% and 34% versus 25%), although only the difference versus “others” was statistically significant.
Patients with an adult child or “other” partner randomized to placebo were doing worse at baseline than those with spouse partners on the Alzheimer’s Disease Assessment Scale-Activities of Daily Living (P=0.04), though not at 18 months and without any significant difference in multivariate models.
No baseline differences emerged by partner type for the Mini-Mental State Examination, Clinical Dementia Rating scale Sum of the Boxes score, or Alzheimer’s Disease Assessment Scale-cognitive subscale.
A limitation was that the analysis included only federally-funded studies, conducted largely by academic trial sites.
“It is unclear how the current results may relate to larger trials, including those supported by industry, which recruit to more diverse site types,” Grill’s group concluded.
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