Earlier Health Conditions Tied to Subsequent Dementia

Some health conditions associated with dementia appeared early and consistently long before diagnosis, while others became significant much later, a cohort study suggested.

For people with a subsequent diagnosis of Alzheimer’s disease, the earliest and most consistent associations at all time points over a 15-year span included depression, erectile dysfunction, gait abnormalities, hearing loss, and nervous and musculoskeletal symptoms, reported Lori Beason-Held, PhD, of the National Institute on Aging in Baltimore, and co-authors.

For those eventually diagnosed with vascular dementia, the earliest and most consistent associations across 13 years were an abnormal electrocardiogram (EKG), cardiac dysrhythmias, cerebrovascular disease, non-epithelial skin cancer, depression, and hearing loss, the researchers reported in Annals of Neurology.

“While hypertension, cerebrovascular disease, and depression are most commonly associated with dementia in the literature, there is some variability in the health conditions linked to dementia,” Beason-Held and colleagues wrote. “The timing of the onset of these health conditions may also be especially important, but less is known about the years immediately preceding dementia diagnosis.”

“It is critical that we understand the connection between physical and cognitive health as our aging population continues to grow,” the researchers added. “Our results reinforce the need for medical intervention and treatment to lessen the impact of health conditions that occur with age, which could potentially reduce the risk of future dementia in our older patients.”

Beason-Held and co-authors reviewed medical records of participants in the ongoing Baltimore Longitudinal Study of Aging (BLSA). They evaluated data for 347 people with Alzheimer’s disease, 76 people with vascular dementia, and 811 control participants without dementia; participants had a mean age of 80 at diagnosis. Those with Alzheimer’s and vascular dementia were matched with controls based on age, sex, and follow-up period.

The researchers looked at relationships between ICD-9 codes and dementia status across all timepoints (up to 15 years for Alzheimer’s disease and up to 13 years for vascular dementia), at 5 years and 1 year before dementia diagnosis, and at the year of diagnosis, controlling for age, sex, and length of follow-up.

Health conditions associated with subsequent Alzheimer’s disease dementia most commonly were hearing loss (39% of participants), urinary incontinence (23%), and depression (11%). Cardiomegaly, urinary incontinence, non-epithelial skin cancer, and pneumonia were not significant until 1 year before Alzheimer’s diagnosis.

People subsequently diagnosed with vascular dementia most commonly had hearing loss (49% of participants), abnormal EKG (41%), cardiac dysrhythmias (37%), and atrial fibrillation (30%). Atrial fibrillation, cerebral artery occlusion, essential tremor, and abnormal reflexes were not significant until 1 year before vascular dementia diagnosis.

These time-dependent findings are important “not only from a clinical standpoint, but may help explain the variability of results from studies examining different intervals prior to dementia diagnosis,” Beason-Held and colleagues observed.

“Unlike Alzheimer’s disease, which had a high number of significant codes for circulatory, dermatologic, genitourinary, mental disorders, and sense organs categories, the majority of associations in vascular dementia involve the circulatory category including both cardiovascular and cerebrovascular codes, and neurological health conditions,” the researchers noted.

“These findings highlight differences between the two dementia types and add to our knowledge of the timing of health comorbidities in relation to the progression of vascular-related dementia,” they added.

Limitations of the study included a relatively small number of participants with dementia, which may be due to the characteristics of the BLSA. “Our participants are generally highly educated and receive regular medical exams, so they are aware of health comorbidities and seek treatment when warranted. Both characteristics can reduce the risk of dementia,” Beason-Held and co-authors noted.

“Those who are developing cognitive issues may also seek more medical attention than those who are not, resulting in increased reporting of less common dementia-related health conditions, such as the dermatologic conditions observed in the Alzheimer’s disease group,” they pointed out. In addition, disease severity may play an important role, but that information was not available.