Dementia deaths may be nearly three times higher than current estimates

Dementia may be linked to nearly three times more deaths in the United States than official records show, according to results of a prospective cohort study published in JAMA Neurology.

“Comparisons of vital statistics with other data sources suggest that physicians and medical examiners substantially underreport [Alzheimer’s disease and related dementias] on death certificates,” Andrew C. Stokes, PhD, of the department of global health at Boston University School of Public Health, and colleagues wrote. “In a community-based, prospective epidemiologic study, only one-quarter of deaths in patients with dementia had [Alzheimer’s disease] listed on the death certificate. Another study with adjudicated records showed that dementia cases were often coded using one of several more immediate causes of death, such as pneumonia, sepsis, and cardiovascular disease.”

Potential reasons for this underreporting include multiple comorbidities among individuals with Alzheimer’s disease and related dementias who die, which complicates identification of one underlying cause; reduced ability of individuals to report symptoms and receive diagnosis because of cognitive impairment; and lack of diagnosis because of stigma. Results of prior studies suggested Alzheimer’s disease and related dementias may be underdiagnosed among more than half of individuals in this population.

Stokes and colleagues sought to determine the extent of this underreporting by estimating the percentage of deaths attributable to dementia in the U.S. They analyzed data of 7,342 noninstitutionalized individuals aged 70 to 99 years with baseline exposure assessment in 2000 and follow-up through 2009. Participants ranged in age from 70 to 79 years (64%), 80 to 89 years (31%) and 90 to 99 years (5%). The investigators used Health and Retirement self- or proxy-reported cognitive measures and the validated Langa-Weir score cutoff to identify at baseline dementia and cognitive impairment without dementia. Further, they used Cox proportional hazards regression models to estimate hazard ratios relating dementia and cognitive impairment without dementia status to all-cause mortality. They compared results with information on cause of death from death certificates.

Results showed dementia was linked to 13.6% (95% CI, 12.2-15) of deaths between 2000 and 2009. Non-Hispanic Black participants had a significantly higher mortality burden of dementia of 24.7% (95% CI, 17.3-31.4) vs. 12.2% (95% CI, 10.7-13.6) for non-Hispanic white participants. Further, adults with less than a high school education had a dementia mortality burden of 16.2% (95% CI, 13.2-19) vs. 9.8% (95% CI, 7-12.5) vs. those with a college education. The researchers reported that underlying cause of death recorded on death certificates placed the mortality burden of dementia at 5% (95% CI, 4.3-5.8), which underestimated the contribution of dementia to mortality in the U.S. by a factor of 2.7, for an increase from 5% to 13.6%. The underestimation increased further after incorporating deaths attributable to cognitive impairment without dementia.

“Future research could examine the extent to which deaths attributable to dementia and underestimation of dementia as an underlying cause of death on death certificates might have changed over time,” Stokes and colleagues wrote. “These results suggest that the mortality burden of dementia may be greater than recognized and highlight the importance of expanding access to population-based interventions focused on dementia prevention and care.”