Higher income leads to earlier dementia diagnosis, less severe disease at diagnosis

Patients with a higher household income received a dementia diagnosis earlier than individuals with a lower household income, indicating a “social inequality” in dementia evaluations, according to findings published in JAMA Network Open.

“... To our knowledge, no register-based nationwide study has been conducted on [household income] and its association with the diagnostic evaluation for dementia,” the researchers wrote. “Herein, we conducted a nationwide study of individuals in Denmark who had a referral for a first-time diagnostic evaluation for dementia in 2017 to 2018. Our objective was to investigate whether [household income] is associated with dementia diagnosis and cognitive severity at time of diagnosis.”

Jindong Ding Petersen, PhD, MSc, a visiting researcher in the Research Unit of General Practice at the University of Southern Denmark, and colleagues conducted a population- and register-based cross-sectional study to determine whether household income was related to dementia diagnosis and cognitive severity at the time of diagnosis. The researchers examined health, social and economic data from Danish national registries in a study population that included individuals who received a first-time referral for a diagnostic evaluation for dementia between January 1, 2017, and December 17, 2018. Annual household income served as a proxy for socioeconomic status.

Dementia diagnoses — including Alzheimer’s disease, vascular dementia, mixed dementia, dementia with Lewy bodies, Parkinson’s disease dementia or other — and cognitive stage at the time of diagnosis — including cognitively intact, mild cognitive impairment but not dementia, or mild, moderate or severe dementia — served as the main outcome measure. The researchers used univariable and multivariable logistic and linear regressions adjusted for age group, sex, region of residence, household type, period (2017 and 2018), medication type and medical conditions to look for a possible association between household income and dementia diagnosis. They conducted data analysis between October 2019 and December 2020.

Petersen and colleagues included 10,191 individuals in the study (mean age, 75 years; 53.7% women). Most patients in the study (n = 8,844; 86.8%) received a dementia diagnosis.

The researchers found that individuals with a household income in the upper threshold compared with the lower threshold were less likely to receive a dementia diagnosis following referral (OR = 0.65; 95% CI, 0.55-0.78). Additionally, those patients in the upper threshold who did receive a diagnosis of dementia had a less severe cognitive stage (beta, 0.16; 95% CI, 0.21 to 0.1). Petersen and colleagues did not observe a significant difference among individuals in the middle household income threshold compared with individuals in the lower threshold regarding dementia diagnosis (OR = 0.92; 95% CI, 0.77-1.09) and cognitive stage at diagnosis (beta, 0.01; 95% CI, 0.04 to 0.06).

“People with higher [socioeconomic status] often have higher educational attainment and higher paying jobs that require certain levels of intellectual function; perhaps individuals with more cognitively demanding jobs can more easily perceive their own cognitive changes, thus leading them to consult with a physician earlier,” the researchers wrote. “In addition, higher educational level not only has been associated with a reduced risk of dementia but is believed to lead to better understanding of dementia and better awareness of the symptoms for early detection and diagnosis.”

Previous systematic reviews found educational deficits to be “a major factor” in delayed diagnosis of dementia, according to Petersen and colleagues. Other factors, including fear of the treatment for the diagnosis, denial, stigma surrounding dementia and living alone, can also prevent individuals from seeking out a diagnostic evaluation for dementia, the researchers noted. Additionally, lack of awareness and/or lack of knowledge about dementia may be related to the increase in disease severity at diagnosis for individuals with lower socioeconomic status.

Petersen and colleagues did not determine how many individuals were diagnosed with dementia by general practitioners without the need for further referral, according to the study results.

“Many health care professionals hypothesized that dementia would be undetectable and underdiagnosed in many countries, including Denmark, and that a higher proportion of such undetected cases would likely consist of individuals with lower [socioeconomic status],” the researchers wrote. “However, this hypothesis needs to be investigated further.”

The results of the present study demonstrated “a social inequity” in the diagnostic evaluation for dementia among individuals in Denmark, according to Petersen and colleagues, where socioeconomic status correlated with dementia diagnosis and cognitive severity at the time of diagnosis.

“Affluent individuals seem to have the advantage of receiving earlier diagnosis,” the researchers wrote. “Public health strategies should target people with lower [socioeconomic status] for earlier detection and intervention for dementia.”