Women age 65 and older who endorse subjective memory complaints have an increased risk of cognitive impairment 18 years later, compared with women who do not endorse subjective memory complaints, according to research published online ahead of print October 28 in Neurology. The findings suggest that subjective memory complaints “may be a very early symptom of an insidious neurodegenerative disease process, such as Alzheimer’s disease,” said Allison R. Kaup, PhD, Assistant Professor of Psychiatry at University of California, San Francisco School of Medicine.
Most prior studies that evaluated the association between subjective memory complaints and later cognitive impairment followed participants for only a few years. To investigate the association over 18 years, Dr. Kaup and her research colleagues conducted a study of 1,107 community-dwelling women in the prospective Women, Cognitive Impairment Study of Exceptional Aging, an ancillary study of the Study of Osteoporotic Fractures. All of the women included in the analysis were Caucasian, age 65 or older, and cognitively normal at baseline.
The investigators assessed subjective memory complaints at baseline by having participants answer a “yes/no” question from the 15-item Geriatric Depression Scale: “Do you feel you have more problems with memory than most?” Participants answered the same question four, eight, and 14 years later. A final evaluation of cognitive status was conducted 18 years after the baseline assessment to diagnose mild cognitive impairment (MCI) and dementia.
The researchers used logistic regression to investigate the association between subjective memory complaints over time and risk of cognitive impairment. They adjusted for demographics, baseline cognition, and characteristics that differed between those with and without subjective memory complaints.
The percentage of participants who reported subjective memory complaints was 8.2% at baseline, 5.6% at four years, 7.3% at eight years, and 8.3% at 14 years. Those with subjective memory complaints at baseline had an increased risk of cognitive impairment 18 years later (adjusted odds ratio, 1.7). Excluding participants with baseline depression did not change the effect of subjective memory complaints. Those with subjective memory complaints at four, eight, and 14 years also had an increased risk of cognitive impairment at 18 years, with the strongest association closest to the diagnostic evaluation (adjusted odds ratios of 1.6, 1.9, and 3, respectively).
“This timing pattern suggests that subjective memory complaints may signal an insidious disease process as it first emerges and continues to unfold,” the researchers said. The risk of cognitive impairment at 18 years was higher in women who reported persistent patterns of subjective memory complaints as well as those who answered “yes” to the question at any single evaluation point during the study, compared with women who consistently answered “no.”
The associations, particularly in the earlier years, “are somewhat modest,” said the investigators. “There may be other reasons for an older adult to endorse subjective memory complaints that do not necessarily lead to the development of MCI or dementia.”
The study did not track the exact point at which participants converted to cognitive impairment, and the findings cannot be generalized to men or to other racial or ethnic groups. In addition, some survival bias is likely because the women in the study were generally in good health, the authors noted.
Future dementia prevention trials should target older women with subjective memory complaints as a high-risk group, Dr. Kaup and colleagues said. In addition, the results support the ideas that clinical providers should consider routine assessment of subjective memory complaints in older patients and that relatively brief assessments may be valuable screening tools, they concluded.
—Linda Peckel