Depression significantly increases the risk of developing dementia and cognitive impairment, as reported in the International Journal of Geriatric Psychiatry.
Dementia is a global concern, with cases projected to reach 135.46 million by 2050. While previous research suggests a link between depression and dementia, the nature of this relationship—whether depression is a precursor, risk factor, or consequence—remains unclear. This research led by Nicola Veronese and colleagues clarifies this link by investigating whether depression at baseline increases the risk of dementia over a 15-year period.
The study utilized data from the Survey of Health, Aging, and Retirement in Europe (SHARE), which is a large, longitudinal cohort representing populations from multiple European countries and Israel. This dataset spans 15 years and includes participants who were free of dementia at the beginning of the study. Participants were followed over 15 years, with assessments conducted across eight survey waves (2004–2020). In total, 22,789 participants were included in the final analysis, with the majority being female, and an average baseline age of 64.2 years.
Depression was assessed using the EURO-D scale, a 12-item self-report questionnaire designed to screen for depressive symptoms in older adults. Dementia was identified through self-reports from participants or their caregivers using a single yes/no question on a physician diagnosis of Alzheimer’s disease, dementia, or senility.
Cognitive impairment was evaluated using a memory recall task and a verbal fluency task, both administered at multiple points throughout the study. Participants were considered cognitively impaired if they scored 1.5 standard deviations below the age-adjusted mean in both the memory and verbal fluency tasks. Several baseline factors were considered as confounders, including age, sex, marital status, educational level, physical activity, alcohol consumption, smoking, and the presence of chronic health conditions (multimorbidity).
Over the course of 15 years, 1,419 participants developed dementia. Individuals who reported depressive symptoms at baseline had a significantly higher risk of developing dementia, with the overall risk increased by 74%. Younger individuals (under 60) with depression were more likely to develop dementia compared to their older counterparts. Among participants under 60, the risk of dementia was more than twice as high for those with baseline depression compared to those without.
Further, individuals with depressive symptoms had a 15% increased risk of cognitive impairment. This association was again stronger in younger participants, indicating that early-life depression could have long-term effects on cognitive health.
Importantly, among the individual depressive symptoms measured by the EURO-D scale, loss of concentration emerged as the strongest predictor of future dementia. This suggests that particular symptoms of depression may be more relevant to the risk of cognitive decline than others. There were also regional differences, with Mediterranean countries showing a stronger association between depression and dementia risk than other parts of Europe.
A key limitation of the study is its reliance on self-reported data for both depression and dementia, which may introduce reporting biases.
Overall, this study highlights the importance of addressing depression, particularly in younger adults, as a potential strategy for reducing the risk of dementia and cognitive impairment in later life.
The research, “Association between depression and incident dementia: Longitudinal findings from the share study”, was authored by Nicola Veronese, Lee Smith, Ai Koyanagi, Pinar Soysal, Christoph Mueller, Chiara Maria Errera, Giusy Vassallo, Laura Vernuccio, Giuseppina Catanese, Marco Solmi, Ligia J. Dominguez, and Mario Barbagallo.