Depression is a leading cause for disability and contributes significantly to the global disease burden. Comparative data on adults’ and older adults’ depressive disorders is scarce in Upper Egypt.
Our results revealed that low education (47.27%) and illiteracy (12.72%) are more common in late-onset depression, aligning with the results of Schlax et al.  and Park et al. .
Consistent with the findings of Kim et al.  and El-Gilany et al. , our study demonstrated an elevated prevalence of LOD in urban areas (67.27%) and this may be explained by lack of social networks in urban rather than rural areas. Nevertheless, Li and colleagues  illustrated that LOD symptoms are more prevalent in villages compared to cities since cities have easier access to health care, better community-level infrastructure, and higher income.
This work revealed that widowed with LOD (18.18%) are more common than widowed with EOD (7.27%) while unmarried with EOD (29%) are more frequent than unmarried with LOD (5.45%), which is consistent with the results obtained by Guo and his colleagues , who concluded that the old depressed widowed scored higher in depression scales than others. However, these results could be explained by the nature of the age groups in general, as widowed people are more common in old age and unmarried people are more common in young ages.
We found that unemployment is more prevalent among elderly depressed subjects (61.81%) compared to young subjects (25.45%), which can be attributed to the age of retirement (60 years), which is consistent with the findings of Latif  who confirmed that retirement harms mental health by increasing the symptoms of depression. Nonetheless, Mandal et al.  indicated that retiring improves elderly Americans’ mental health.
Our results revealed that low socioeconomic status is more prevalent among old depressed patients (70.9%) than young depressed patients (63.63%), which is in agreement with Domenech-Abella et al.  and Abdo et al. , who stated that low household income is a significant predictor related to old age depression. Domenech-Abella et al.  added that financial difficulties in childhood are a risk factor for depression throughout life, even in late life. Our findings revealed that the comorbidity of chronic medical diseases such as diabetes mellitus, hypertension, ischemic heart disease, and stroke represent a higher risk for depression among older adults (78.81%) than young adults (12.72%). Individuals with LOD usually suffer from severe medical comorbidities as well as poor adherence to treatment, as reported by Papadopoulos et al.  and Hall et al. , who demonstrated that chronic medical illnesses are pervasive in old adults who have depression. Furthermore, Arean and Reynolds  illustrated that many psychosocial stressors (particularly ischemic heart diseases and stroke) are considered risk factors for depression in old seniors. However, Groeneweg-Koolhoven et al.  stated that patients with early and LOD revealed similar predisposing risk factors.
The present study revealed that low mood is a more prevalent symptom among patients with EOD (81.81%) than patients with LOD (70.9%), which is similar to the results of Groeneweg-Koolhoven et al. 
Our results revealed that apathy was highly related to age, as patients with LOD demonstrated higher scores on the apathy scale (57±6) than patients with EOD (49±4), which is compatible with Groeneweg-Koolhoven et al. , who observed that apathy as a symptom is more common in old adults with depression (74.5%) than young adults with depression (53.5%). Additionally, Pimentel et al.  observed that apathy is frequent in LOD and is related to poor outcomes.
Our findings suggest that psychomotor retardation is a more common presentation among old seniors with depression (65.45%) than young adults with depression (30.9%) which is consistent with the results of Aziz and Steffens , who demonstrated that psychomotor retardation is a prominent feature in the elderly with depression. The current study found that cognitive impairment was more common among depressed elders (70.9%) than patients with early-onset depression (47.27%), which aligns with the results of Morimoto et al.  and Hashim et al. , who stated that cognitive disturbance is a common symptom in depressed old seniors, on the other side, Alexopoulos  cited that age-related cognitive impairment and arteriosclerosis in older adults increase the vulnerability to depression. However, age-related cognitive decline is pervasive in older adults. Byers and Yaffe mentioned that  when depression appears in old age, it is difficult to differentiate it from dementia since both illnesses have comparable symptom profiles, particularly when depression impairs cognition and is reported as pseudodementia.
In this study, we found that somatic symptoms were a common presenting symptoms among patients with LOD (61.81%) than patients with EOD (36.36%), which is compatible with the results of Morin et al. , who observed that somatic manifestations were common presenting symptoms in older adults with depression, particularly in family practice clinics. However, physical diseases with somatic complaints are common in the aged population.
Our results revealed that sleep disturbance is much more common among depressed old seniors (81.81%) than depressed young patients (70.9%), which aligns with the results of Naismith et al.  and El-Gilany et al. , who reported that depression in older adults is associated with neuropsychological dysfunction and sleep disturbance. Nevertheless, Naismith et al.  stated that sleep-wake disturbance in older people is a risk factor for depression onset and recurrence. However, sleep disturbance is a frequent complaint in old adults without depression. This piece of work focuses on late onset depression that goes unrecognized by some physicians . Physicians should screen elderly patients for depression, especially those who are widow, unemployed, with low socioeconomic status or have chronic medical illness. According to our findings, we should suspect major depression in elderly with multiple unexplained somatic symptoms after exclusion of organic causes. This will save time and money for the patients that are managed in wrong ways. Also, the presence of somatic complaints is considered a bad prognostic factor in geriatric depression . As insomnia is common presenting symptom in geriatric depression, psychiatrists should tailor the treatment to manage insomnia. In elderly patients presented with cognitive decline, we should put major depression in differential diagnosis as cognitive complaint is a common presenting symptom in late onset depression.
Comparative studies on symptoms and risk factors of depression in young and old adults are limited in Upper Egypt. Patients recruited were unselected and came randomly from the psychiatric clinic. Our work yields clinical insights and provides a direction for future studies on depression across the life span.
As the study is cross-sectional, we did not conclude a cause-effect relationship. There is a possibility of reporting bias as cognitive impairment and sleep disturbance could be a symptom or a cause of depression. It is unclear if these results can be generalized to a population of old and younger adults due to limited number of patients.