Study identifies five depressive symptom trajectories, with stable-high and increasing patterns significantly raising the risk of all-cause mortality.

Study: Association between the depressive symptom trajectories and all-cause mortality in Chinese middle-aged and elderly adults. Image Credit: New Africa/Shutterstock.com

Depression is a widespread condition known to elevate the risk of death from all causes. However, its progression differs significantly between individuals, highlighting the need for more detailed investigation.

A recent study published in Scientific Reports explored how long-term patterns of depression in an older Chinese population influence the risk of all-cause mortality.

Depression – the global picture

About a third of adolescents worldwide have symptoms of clinical depression. In China, observation over one month revealed the presence of significant symptoms of depression in nearly 20% of individuals.

Depression is a risk factor for cardiovascular disease, dementia, and suicidal thoughts and exacerbates other medical conditions. It contributes 45 million disability-adjusted life-years (DALYs) globally. Moreover, it increases the risk of death.

Most studies examining this aspect have been cross-sectional despite the fluctuating nature of depressive symptoms. Many depressed people rebound because of inner resilience, proper treatment, social and family support, positive life events, and/or biological changes.

Major changes in depression intensity have been found in almost 20% of participants in one longitudinal study, but this has not been given adequate weight in the majority of studies. This motivated the current paper.

About the study

The present study included 13,624 people over the age of 45 years. The data came from the China Health and Retirement Longitudinal Study (CHARLS). Depression was assessed using the Center of Epidemiologic Studies Depression Scale-10 (CESD-10).

The trajectories of depression in different groups were modeled and examined for any association with all-cause mortality. Mortality was checked at two points, 2018 and 2020. Other demographic, lifestyle, and medical factors were also used to stratify the participants.

The model incorporated five trajectories for depressive symptoms. These comprised stable-low, stable-moderate, increasing, decreasing, and stable-high. The number of participants in each trajectory was 4,900, 5,250, 1,200, 1.500, and 750, respectively.

Thus, 36% of participants had stable low depressive symptoms, and 39% had stable, moderate symptoms. About 6% had high depressive symptoms. Symptoms increased over time by 9% and decreased by 11%.

There were 1,194 deaths in the whole group, the mortality rate being 8.7%. After compensating for other confounding factors, the mortality risk increased by 30% and nearly 60% among those in the increasing and stable-high symptom trajectory groups, respectively, compared to those with stable-low depression. The risk of mortality from any cause increased from the lowest to the highest symptom trajectory.

There was no significant mortality risk in the groups with decreasing or stable-moderate depression trajectories. The sensitivity analyses revealed the robustness of the findings for most of the groups.

The findings corroborate earlier studies and extend the findings by showing the impact of waning or waxing symptoms with time on the risk of mortality.

The importance of identifying this group through long-term follow-up appears clear. Potential interventions targeting the high-risk groups include pharmaceutical, psychological, exercise-based, and general strategies aiming to enhance the quality of life.

Plausible biological mechanisms have been suggested linking mortality to depression, such as disrupted biofeedback mechanisms, low-grade inflammation, and increased odds of unhealthy lifestyles.

Conclusions

The findings of this study show differing trajectories of depression among middle-aged and older Chinese individuals.

There was an increased risk of all-cause mortality among people who showed increasing or persistently high levels of depression compared to those who had low and stable levels.

No significant increase in risk was found among those with depression at baseline but showed decreasing symptoms over time or those who had moderate but stable depressive symptoms. This suggests that earlier mortality estimates for such groups were overestimated.

Future studies should follow individuals with depression over multiple time points to provide more insight into the association of depression with mortality.