Common conditions that raise dementia risk

Here’s something to ponder: The number of older Americans with dementia dropped 24% between 2000 and 2012. But the number of Alzheimer deaths rose 55% from 1999–2014, according to research cited by alzhemiers.net. 

Possible reasons for a decrease in the prevalence of dementia but an increase in Alzheimer morbidity could be that more people are being diagnosed with the condition. And because there are better treatments for chronic conditions like heart disease and diabetes, more people are living to an age where dementia complications can kill. 

Nevertheless, risks still remain, as outlined in several research studies.

Lipid levels

In a large study published in Dementia and Geriatric Cognitive Studies, Kaiser Permanente researchers examined the relationship between lipid levels and Alzheimer disease (AD) and vascular dementia (VaD) in a multiethnic cohort.^[]

“Midlife serum total cholesterol was associated with an increased risk of AD and VaD. Even moderately elevated cholesterol increased dementia risk,” the authors wrote. “Dementia risk factors need to be addressed as early as midlife, before underlying disease(s) or symptoms appear,” they added.

The data also indicated the overlap between AD and VaD in relation to risk factors, symptoms, and neuropathology, as well as tying both to cardiovascular risk factors. In sum, effective management of heart disease and dementia is transdisciplinary.

Traumatic brain injury

The occurrence of moderate and severe traumatic brain injury (TBI) was one of the first risk factors linked to dementia, with most research supporting the relationship. In particular, individuals with genetic risk factors, such as one or more apolipoprotein E e4 alleles, are most susceptible to dementia following TBI.

The link between mild TBI and dementia, however, has been under debate.

To help settle this question, researchers conducted a large propensity-matched cohort study involving military personnel—among whom the frequency of TBI is particularly high. Per results published in JAMA Neurology, the researchers found that even mild TBI without loss of consciousness (LOC) was correlated with dementia. After compensating for medical and psychiatric comorbidities, the adjusted hazard ratios for dementia were 2.36 for mild TBI without LOC, 2.51 for mild TBI with LOC, 3.19 for mild TBI with unknown LOC status, and 3.77 for moderate to severe TBI.^[]

Old age

It’s no surprise that the risk of dementia increases with age. What is surprising is exactly how fast this risk compounds—especially in the most elderly. Between 65 and 90 years of age, dementia incidence rates increase exponentially, doubling about every 5 years. 

According to the results of a population-based longitudinal study published in Annals of Neurology, rates of dementia increased from 12.7% per year in those aged 90–94 years, to 21.2% per year in those 95–99 years, and to 40.7% per year in those aged 100 years or more.^[]

“Incidence of all-cause dementia is very high in people aged 90 years and older and continues to increase exponentially with age in both men and women,” the researchers wrote. “Projections of the number of people with dementia should incorporate this continuing increase of dementia incidence after age 90 years.”

Diabetes

The link between diabetes/diabetes comorbidities and dementia is well-established. But, because the mechanisms are unclear, it still remains to be elucidated how to act on this association. 

“Although diabetes control has been demonstrated to prevent other diabetes complications, it cannot yet be implemented as a tool for dementia prevention since it is yet unknown which diabetes-related factors (glucose control, presence of complications, comorbidities, type of treatment or other) affects cognition,” wrote the authors of a review article published in Expert Review of Therapeutics.^[]

“Better understanding of the relationships of diabetes and dementia is required,” they added. “Since some diabetes-related factors are on a continuum extending to nondiabetic populations, the insights regarding the association of diabetes with cognition and dementia may extend to nondiabetic populations.”

With respect to antidiabetic medications, the authors explained that uncontrolled serum glucose levels were linked to neurodegeneration, but tighter glucose control minimized cognitive deterioration. Diabetes medications can lead to more hypoglycemic episodes, though, which could increase dementia risk. To date, epidemiologic studies examining the link between dementia risk and antidiabetes drugs have had mixed results. Ultimately, it’s unclear whether taking oral hypoglycemics and insulin decrease dementia risk, per the authors.

Sleep apnea

Sleep apnea can influence cognitive functioning in several domains, particularly attention and memory. Cognitive deterioration is also age-dependent in apneic patients.

The effects of sleep apnea may extend to increased dementia risk, according to the results of a retrospective Taiwanese study published in PLOS ONE. After accounting for covariates, the researchers found that patients with sleep apnea (SA) had a 1.70–times greater risk of developing dementia within 5 years compared with sex- and age-matched patients without the condition. ^[]

“The findings from our national population-based cohort study provide support for the link between SA and dementia,” the authors wrote. “Although few treatments are available for dementia, highly effective treatments are available for SA. Studies on SA treatment have indicated that continuous positive airway pressure (CPAP) therapy can be effective in reducing SA events and their associated cognitive and affective sequelae.”