Subjective Cognitive Decline Linked to Future Dementia RiskSubjective Cognitive Decline Linked to Future Dementia Risk In a recent study published in _JAMA Psychiatry_, researchers investigated the connection between subjective cognitive decline (SCD) and the risk of developing mild cognitive impairment (MCI), Alzheimer’s disease (AD), and dementia. Study Design The study involved cognitively normal adults aged 60 or older from the Framingham Heart Study. Participants were followed from 2005 to 2019, and SCD was assessed through questionnaires at multiple visits. MCI, AD, and dementia were diagnosed using standard criteria. Genetic risk factors, including the presence of AD-associated genes, were also considered. Key Findings * SCD was significantly associated with an increased risk of MCI, AD, and dementia. * People with SCD were more likely to have memory problems and report higher rates of depression. * SCD typically occurred several years before the onset of cognitive impairment. * The risk of cognitive decline remained significant even after accounting for genetic predisposition and other factors. Implications The study highlights the importance of monitoring SCD in older adults. SCD may be an early indicator of future cognitive impairment, and individuals who experience SCD should be followed closely for further cognitive changes. Early detection and intervention strategies can potentially improve outcomes and enhance quality of life. Limitations * The study included a predominantly White population, so results may not be generalizable to other ethnic groups. * SCD cases may have been underestimated due to irregular assessment. * AD biomarkers were not used to confirm diagnoses. Further Research Future studies are needed to address these limitations and investigate the predictive value of SCD in diverse populations. Additionally, research should explore the underlying mechanisms linking SCD to cognitive decline and identify effective interventions to prevent or delay future cognitive impairment.
In a recent study published in the journal JAMA Psychiatryresearchers examined the risk of subjective cognitive decline (SCD) in cognitively normal adults for developing mild cognitive impairment (MCI), Alzheimer’s disease (AD), and all-cause dementia.
Their findings show that SCD is significantly associated with an increased risk of future cognitive impairment and dementia, suggesting that SCD may be an independent risk factor for these conditions, alongside genetic predisposition.
Study: Subjective cognitive decline plus longitudinal assessment and risk of cognitive impairment. Image: Lightspring / Shutterstock
Background
Detecting AD early, before symptoms fully develop, is crucial for effective treatment and prevention. One way to recognize early signs is through subjective cognitive decline (SCD), which occurs when people notice their memory or thinking problems even though standard tests show them to be normal.
Research has shown that SCD can be an early indicator of future memory problems or AD. However, most of the research has been done on people who seek medical care and may be at higher risk of developing AD.
Community-based studies, which examine people who do not seek medical care, provide a more accurate picture of how SCD affects the general population. However, these studies often have limitations, such as small sample sizes, one-time assessments, and less rigorous testing.
About the study
To fill the research gaps, the current study used long-term data from the Framingham Heart Study, which follows a large group of people over a long period of time.
Participants aged 60 years and older with normal cognition were included and followed from 2005 to 2019. In the study, SCD was assessed by asking questions about memory problems at multiple visits.
Researchers used standard criteria to diagnose MCI, AD, and all-cause dementia. They collected genetic information, including the presence of genes associated with AD risk, from blood samples and calculated a polygenic risk score (PRS) to measure overall genetic risk for AD.
Statistical models compared the risk of developing MCI, AD, and dementia between people with and without SCD after adjusting for factors such as age, sex, education, genetic risk, depression, and other health conditions. Additional analyses looked at specific features of SCD (called SCD-plus) to better understand their role in predicting cognitive decline.
By including these genetic factors and specific features of SCD (SCD-plus), the study aimed to gain insight into the risk of developing serious memory problems in the general population.
Findings
The study included 3,585 individuals with a mean age of 68. Approximately 55.1% of the sample were women and 91.6% were non-Hispanic white individuals. Of the participants, 50.3% were college graduates and 21.5% carried a gene linked to AD. Participants were followed for approximately 2.1 valid visits per person.
During the study period, 6.6% of participants developed MCI, 2.0% developed AD, and 2.5% developed dementia of any cause. On average, SCD occurred 4.4 years before MCI, 6.8 years before AD, and 6.9 years before any dementia. The average age of onset of SCD was 69.8 years.
People with SCD were more likely to be women at all visits and reported higher rates of depression. Cognitive impairment was higher in this group compared to the group without SCD: MCI (8.6% vs. 5.8%), AD (3.4% vs. 1.5%), and all-cause dementia (3.9% vs. 2.0%).
Survival analysis showed that SCD was significantly associated with time to develop MCI, AD, and all-cause dementia. Adjusted for age, sex, and education, the hazard ratios (HR) for SCD were 1.60 for MCI, 4.33 for AD, and 2.17 for all-cause dementia.
After accounting for genetic predisposition to dementia, the HRs remained significant: 1.57 for MCI, 2.98 for AD, and 2.14 for all-cause dementia. Depression and other cardiovascular factors reduced the HRs slightly, but SCD remained a significant predictor.
The results showed a strong and consistent association between SCD and the risk of future cognitive impairment, underscoring the importance of monitoring SCD in older adults.
Conclusions
This large longitudinal study found that SCD was a significant predictor of MCI, AD, and all-cause dementia, which is consistent with previous research. SCD typically preceded MCI by 4.4 years, AD by 6.8 years, and all-cause dementia by 6.9 years.
The strengths of the study include the large community-based sample and the longitudinal design, which increases the reliability of the findings. However, limitations include the low rates of cognitive impairment, possible underestimation of SCD cases due to irregular assessment, and the lack of AD biomarkers.
Future research should address these limitations and examine the predictive value of SCD in more diverse populations to improve early screening and intervention strategies.
Journal reference:
- Subjective cognitive decline plus and longitudinal assessment and risk of cognitive impairment. Kang, M., Li, C., Mahajan, A., Spat-Lemus, J., Durape, S., Chen, J., Gurnani, A.S., Devine, S., Auerbach, S.H., Ang, T.F.A., Sherva, R., Qiu, W.Q., Lunetta, K.L., Au, R., Farrer, L.A., Mez, J. JAMA Psychiatry (2024), doi:10.1001/jamapsychiatry.2024.1678, https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2820771
