According to a recently published study, International Journal of Geriatric Psychiatry A significant association was found between depression and an increased risk of developing dementia. The study, conducted over a 15-year period, found that people who had depression at the start of the study were 74% more likely to develop dementia than those who did not. Additionally, people with depression developed dementia about two years earlier. These results highlight the importance of early detection and treatment of depression to prevent future cognitive decline.
The world’s population is ageing rapidly, with the number of people aged 65 and over projected to double from 703 million in 2019 to 1.5 billion by 2050. This demographic change is expected to lead to a significant increase in the number of people with dementia, from 47.5 million in 2015 to an estimated 135.46 million by 2050. With approximately 7.7 million new cases of dementia expected to occur each year, understanding and mitigating risk factors for dementia is a public health priority.
Dementia is a general term used to describe a decline in cognitive function that interferes with daily life. It can include a range of symptoms, including memory loss, difficulty solving problems, language problems, and impaired reasoning and judgment.
Dementia is caused by damage to brain cells and can result from a variety of diseases and conditions, but the most common cause is Alzheimer’s disease. It mainly affects older people, but is not a normal part of the aging process.
Previous studies have suggested a possible association between depression and dementia, but the exact nature of this relationship remains controversial. Some studies suggest that depression may be an early symptom of dementia, while others propose that it may be a risk factor or comorbidity of dementia. The current study aimed to clarify this relationship by investigating whether depression at baseline increases the risk of developing dementia during a long-term follow-up period.
“I’ve been a geriatrics physician for about 10 years, and I think it’s important to confirm in large population studies that depression could be a risk factor for dementia and mild cognitive impairment,” said study author Nicola Veronese, associate professor at the University of Palermo.
“Indeed, depression, unlike dementia, is a disease that is amenable to pharmacological and non-pharmacological treatments. We hope that our study will encourage further research to examine whether treating depression can reduce the risk of dementia.”
In this study, Survey on Health, Ageing and Retirement in Europe (SHARE)is a large, multidisciplinary international panel study. The SHARE survey includes a representative sample of individuals aged 50 years and older from 27 European countries and Israel. Data were collected through multiple survey rounds that began between 2004 and 2006 and continued until 2019/2020.
Participants were assessed for depressive symptoms using the EURO-D scale, a 12-item questionnaire that measures different aspects of depression, including pessimism, sleep quality, concentration, etc. A score of 4 or higher on the EURO-D scale is indicative of depression.
Incidence of dementia was determined by self-report or caregiver/family report, asking participants whether a physician had given them a diagnosis of Alzheimer’s disease, dementia, or senile dementia. Cognitive impairment was assessed using a combination of memory recall and verbal fluency tasks, and participants who performed significantly below the norm for their age stage were classified as having cognitive impairment.
Of the 22,789 participants in the study, 24.9% were diagnosed with depression at baseline. These participants were generally older, more likely to be female, less likely to be married or educated, and had a higher rate of chronic illnesses and limitations in daily activities.
During the 15-year follow-up period, 1,419 participants developed dementia, corresponding to an incidence rate of 7.31 per 1,000 person-years. The study found that having depression at baseline significantly increased the risk of dementia by 74%. This association was particularly strong in younger participants; people under 60 were twice as likely to develop dementia if they had depression.
“The most important takeaway here is that depression has a cognitive dimension that must always be taken into account when working with someone suffering from this condition,” Veronese told PsyPost.
Interestingly, the study also found that certain symptoms of depression, such as difficulty concentrating, were strong predictors of dementia. Other symptoms, such as pessimism and fatigue, were also associated with an increased risk, but poor sleep was not.
“We were surprised to find that not only depression, but specific features of a tool used to detect depression, could predict the onset of dementia,” Veronese said.
Despite the large sample size and long follow-up period, this study has several limitations. First, depression assessment was based on self-reported symptoms rather than clinical diagnosis, which may introduce bias. Similarly, dementia diagnoses were self-reported, which may not have accurately captured all cases. The study did not distinguish between different types of dementia, which may have different risk profiles related to depression.
“The SHARE study was not designed to specifically investigate the relationship between depression and dementia. The diagnosis was based solely on tools and self-reported information, which could bias the findings,” explained Veronese.
Another limitation is the possibility of reverse causation, where early symptoms of dementia may be mistaken for depression. Although the study attempted to address this issue by excluding cases diagnosed with dementia in the first 5 years of follow-up, this possibility remains.
Veronese said future studies should focus on confirming these findings in other populations and exploring whether treating depression can reduce the risk of dementia. Research can also aim to identify the biological mechanisms that link depression and dementia. For example, examining the role of inflammation, hormonal changes, and genetic predisposition could provide insight into how these conditions are related.
the study, “The association between depression and the onset of dementia: Longitudinal findings from the SHARE studyThe authors of “The Secrets of Italian Literature” are Nicola Veronese, Lee Smith, Ai Koyanagi, Pinar Soysal, Christoph Müller, Chiara Maria Herrera, Giusi Vassallo, Laura Vernuccio, Giuseppina Catanese, Marco Sormi, Ligia J. Domínguez and Mario Barbagallo.
