Background
Dementia is a common neurodegenerative disorder characterized by progressive cognitive impairment and decreased ability of daily living [
1], with or without behavioral and psychological symptoms of dementia (BPSD).
Neuropsychiatric symptoms (NPSs) have been viewed as “non-cognitive” symptoms of dementia, encompassing impairments of mood, anxiety, drive, perception, sleep, appetite, and behavioral disturbances such as agitation or aggression [
2]. Previous studies have shown associations between NPSs and poorer outcomes in dementia patients manifesting as greater caregiver burden [
3], higher rates of institutionalization, poorer quality of life [
4], and accelerated progression to severe dementia or death [
5]. On the other hand, NPSs were identified as a risk factor for dementia [
6]. Specifically, the presence of NPSs increased the incidence of dementia in patients with mild cognitive impairment (MCI), a prodrome of AD [
7]. Previous studies exhibited that people who presents anxiety, negative affect, hostility, pessimism, hopelessness, and perceived constraints were at a 20–30% increased risk of dementia [
8]. Anxiety has been previously associated with both cognitive decline [
9] and risk of dementia [
10]. All these findings support the point that NPSs may be viewed as risk factors for dementia.
Relevant to MCI, mild behavioral impairment (MBI) was proposed as MCI of the frontotemporal type [
11]. MBI is an umbrella concept describing a syndrome in which late-onset psychiatric symptoms, including major depression, generalized anxiety, delusional disorder and so forth are early manifestations of neurodegenerative disease. The updated MBI criteria describes that MBI is a syndrome of BPSD starting later in life (age ≥ 50 years) and persisting at least intermittently for 6 months [
12]. The details of the criteria consist of (1) persistent behavioral changes and mild psychiatric symptoms, especially disinhibition, (2) no serious cognitive complaints, (3) normal activities of daily living, and (4) absence of dementia [
13‐
15]. More importantly, MBI was hypothesized to increase the risk for dementia, especially for FTLD, whether or not significant cognitive symptoms are present. Indeed, Taragano and colleagues proved that over 70% of patients with MBI developed into dementia [
16]. These studies suggest that clinicians should pay close attention to the psychiatric patients started with NPSs over 50 years old.
Despite of the advances in MBI and NPSs mentioned above, no one assessed the association between each NPS and dementia, especially in middle aged and senior patients with late-onset psychiatric symptoms. The present study aimed to figure out to what extent individual NPS and certain demographic factors increased the risk of dementia in psychiatric inpatients with first episode age over 50 years. These patients were diagnosed as various types of dementia or non-demented psychiatric disorders (NDPD) when they were discharged from the psychiatry department. The two groups of patients were compared on demographic information and medical records to explore associations between these variables and dementia and NDPD in the patients investigated. Furthermore, we figured out the risks of some demographic factors and certain NPS for dementia using binary logistic regression analysis.
Discussion
In the present study, 41.73% of psychiatric inpatients with late-onset psychiatric symptoms were diagnosed with dementia, indicating a high incidence of dementia among these patients. This result is in line with previous studies reporting that 40% of psychoses in elder adults were due to AD and other dementias [
25]. The subtypes of dementia found in the psychiatric inpatients included AD (60.38%), DLB (3.77%), FTLD (11.32%), MCI (13.21%), dementia due to neurosyphilis (5.66%), Parkinson’s disease (3.77%), and VD (1.89%). These figures are different from the population-based studies on the prevalence of dementia showing that VD was the second most common cause of dementia followed by FTLD [
26,
27]. Certainly, this difference could be attributed to the fact that we selected psychiatric inpatients with late-onset psychiatric symptoms in present study. This is a highly selected group, not necessarily representative of demented patients as a whole. The frequencies of different dementias simply reflect their admissions in this study. So the subtype of dementia patients may or may not be overrepresented in a psychiatric inpatient population.
The NDPD in this study consisted of nine individual diagnoses, except for schizophrenia, indicating a very low prevalence of schizophrenia in psychiatric inpatients with first episode age over 50 years old. This interpretation is consistent with previous studies showing that the incidence of first episode schizophrenia was 0.03% in people over 40 [
28]. In another research, the prevalence of very late-onset schizophrenia was only 0.1–0.5%, and the patients were characterized by psychotic symptoms such as delusions and hallucinations [
29]. In contrast, people over 50 years old showed a high incidence of dementia. Previous studies suggested that FTLD most occured at 45–65 years old [
21]. Women over 65 years old have a 7% probability of suffering from AD. And for every 5 years of age increases, the risk of dementia doubles [
22]. MBI was also at a high risk (up to 71.5%) of developing dementia [
23]. These findings suggest that dementia had a high incidence in the psychiatric inpatients with first-episode mental disorder after 50 years old.
As expected, the incidence of dementia patients increased with first episode age in the present study. This finding is in accordance with a recent age-related prevalence estimates for dementia in the UK, reporting a prevalence of 1.3% in the entire UK population, but 7.1% in those aged 65 or over [
30]. In addition, we found that males accounted for a higher proportion relative to females in dementia patients. This seems to be different from the same population-based study in UK showing that men and women under 85 developed dementia at comparable prevalence, and females had a higher prevalence than males after 85 years old. This inconsistence is not surprising as the UK study is a population-based study which had a large number of older persons over 85. The present study is a clinical research with a relatively small sample having only a small number of patients over 85 years of age and therefore did not represent the entire population of China. However, our finding that most (64.86%) of NDPD inpatients were females is in line with the previous studies pointing out the association of female sex, among the other factors, with some psychiatric disorders (including depression, and stress-related disorder) in older adults [
31,
32].
It is not surprising that 58.49% of dementia patients presented CD as initial symptom while the remaining 41.51% showed NPS as initial symptom. These results are meaningful and will benefit the early diagnosis of dementia, not only by emphasizing the importance of assessment of cognitive functions for suspected patients, but also reminding family members and caregivers of NPSs that may present in advance of CD. Indeed, the diagnosis of dementia in older adults can be challenging to primary care providers because early symptoms of dementia like memory impairment may not be apparent and minor forgetfulness may be difficult to be distinguished from normal ageing. In contrast, the vast majority (94.6%) of NDPD inpatients presented NPSs as initial symptoms, confirming the usefulness of NPI in identifying this major diagnosis. In support of the accurateness of the two major diagnoses, patients with NDPD presented an averaged MMSE score (26.12), which is slightly higher than the cutoff point (24), whereas they had an ADL score of 17.28 which is lower than the established cutoff indicating that the NDPD inpatients had no mild impairment in daily living activities.
The main aims of this study were to figure out the association of each NPS with dementia and specify to what extent individual NPS increased the risk of dementia in psychiatric inpatients started with NPSs over 50 years old. For the first aim, we compared the total score of NPI and incidence of each symptom in dementia inpatients to those with NDPD. We found that dementia group had a significantly higher NPI (10.34 ± 4.48) than patients with NDPD, confirming that mild NPSs is a common phenomenon in enrolled dementia inpatients, even more common/severe compared to NDPD inpatients. These results added evidence that NPSs are exceedingly prevalent in dementia patients hospitalized in psychiatric ward [
33,
34]. Indeed, noncognitive symptoms of dementia occur in 98% of individuals at some point during their disease process as reported in clinical settings [
35]. Furthermore, we found that the incidences of individual NPS were different between the two major diagnoses. Specifically, AMB, agitation, apathy, hallucination, and irritability presented at higher frequencies in dementia inpatients relative to those with NDPD, whereas appetite and eating disorder happened in NDPD inpatients more frequently. The two groups were comparable in incidences of the remaining NPSs.
The results of binary logistic regression revealed that agitation and apathy remained to be high risk factors of dementia in late-onset psychiatric inpatient after adjusted for gender and first episode age. This concluding result is in line with a previous population-based study which evaluated the frequency of symptoms in people with dementia and reported that apathy was the most frequent symptom, followed by depression and agitation [
36]. The majority of patients in the cited study was AD, along with VD, Parkinson’s disease dementia, and others. These are coincidently similar to the dementia subtypes in the present study. This coincidence reminds us to be cautious when generalizing the conclusion, i.e., the presentation frequencies of each individual NPS in dementia patients may vary depending on patient population. In support of this reminding, a previous study with patients admitted to a geriatric psychiatry unit in Germany reported that aggression was the most frequent symptom (seen in approximately 57% of patients) [
37]. In the other studies, however, apathy was the most common (affecting up to 76% of patients) and lasting NPS in AD patients [
36,
38].
While recognizing the clinical relevance of the results shown here, we were aware of the limitations of this study. First, the sample of this study was relatively small thus did not allow further analysis on each subtype of dementia and individual NDPD. Second, for the same reason, it did not allow powerful statistical analysis on the comorbidity data which showed no inter-group differences. Third, the diagnoses lacked solid supports from sophisticated laboratory and radiological tests, some of which are very expensive in China and must be paid out of patients’ pocket. Forth, MMSE is a cursory test to assess the cognitive impairment in different domains. It has obvious “ceiling effect” and “floor effect” leading to low specificity and sensitivity. The memory item of it is not enough to be considered a validated assessment of the memory domain. Nonetheless, the data presented in this study encourage us to further investigate the diagnosis and treatment of patients with dementia and NDPD in future studies, in which cognitive function evaluation of the patients will be done by more reliable and specific methods.
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