Predictors of psychiatric rehospitalization among elderly patients

Background

The population in Hong Kong and the proportion of elderly people are increasing rapidly. Pamela Youde Nethersole Eastern Hospital is a regional hospital under the Hospital Authority serving the eastern district of Hong Kong Island. The characteristics of elderly patients were different from that of general adults, for example, more of them suffered from cognitive disorders, they were more often hospitalized due to medical comorbidities, and they might require placement such as old age homes after discharge. Despite many psychiatric readmission studies were already available in the literature, surprisingly very few of them were targeted to elderly patients only.

Rehospitalization had been regarded as a useful indicator to measure quality of care provided by hospitals worldwide^1,2. Since there are only a small number of elderly psychiatric rehospitalization studies available, studies involving elderly patents and patients of all ages (including the elderly) were reviewed. Socio-demographic factors that were identified as significant in previous studies included: age^3–10, gender^5,8,11–14, ethnicity¹⁵, marital status^14,16–20, education level¹³, and type of residence^{5,6,8,10,15,17,22,23}. Clinical factors significantly associated with rehospitalization included: length of inpatient stay^{3,5,9,10,16,19,24,25}, primary psychiatric diagnosis^{4,5,8,9,11,14,18,19,21,22,24,26}, presence of psychiatric comorbidities^4,17,27, presence of medical comorbidity^21,27, cognitive impairment^3,25, referral for aftercare services^6,7,29,30, history of suicidal behaviors¹², history of violence^11,25,28,31 and number of previous psychiatric admissions^{7,8,15,20,25,32,33}. Many of the articles adopted a retrospective design and involved psychiatric patients of all ages, while very few were specifically targeted elderly patients^{20,22,27,33,34}, and no such data was available for elderly psychiatric patients in Hong Kong. Therefore this study was conducted to identify risk factors in attempt to reduce rehospitalization, so mental health services could be utilized more effectively in view of the increasing needs from the aging population.

Methods

The aim of this retrospective cohort study is to determine predictors for psychiatric rehospitalization over 2 years among elderly patients after they were discharged from psychiatric wards.

Data analysis

Results

Figure 1 presents the formation of the study population and separation into the subgroups. Of all 454 discharge episodes from psychiatric wards of Pamela Youde Nethersole Eastern Hospital with patients aged 65 and over from 1 March 2010 to 29 February 2012, 368 individuals formed the study population after screening for the exclusion criteria. 77 individuals were readmitted while 291 individuals were not during the 2 year follow up period. The cumulative rehospitalization rate at 2 years was 20.9%.

Figure 1. Formation of the study population and separation into the subgroups.

Concerning the socio-demographic characteristics of the study population, the median age was 76 and male to female ratio was 1 to 1.61. 98.1% of individuals were Chinese. 47% of the study population was married, 39.7% was widowed, 7.9% was divorced or separated and 5.4% was single. For education level, 41.6% was less than primary, 31% was primary, 20.6% was secondary and only 6.8% was tertiary or above. 52.7% of the study population lived at home with family or friends, 33.7% was living in placement, 9% lived alone at home and 4.6% lived with maid at home. Regarding the clinical characteristics of the study population, the median length of inpatient stay for the study population was 27 days. The median for number of chronic physical illnesses was 2 and number of previous admissions was 0. 96.2% of individuals had non-PFU status. For the primary psychiatric diagnosis, 37.2% had cognitive disorders, 32.9% had depressive disorders, 23.1% had psychotic disorders, 4.1% had bipolar disorders and the remaining 2.7% suffered from other mental illnesses. 20.1% of the study population suffered from psychiatric comorbidities. Regarding MMSE scores, 32.3% of the study population scored 11–20, 18.5% scored 21–26, 13.6% scored less than 10, 9% scored over 26, and 26.6% did not have scores documented. 69.8% of individuals had referral to other psychiatric disciplines upon discharge. Lastly, 24.2% had history of suicidal behaviors and 15.8% had history of violence in their lifetime.

Univariate analysis for socio-demographic factors and clinical factors of the study population are shown in Table 1 and Table 2 respectively. Results of subsequent multiple logistic regression are shown in Table 3. Four significant factors were identified with their odds ratios calculated. Referral to other psychiatric disciplines upon discharge (p< 0.001, OR=0.325) was associated with a lower risk of rehospitalization, while the other three factors including history of suicidal behaviors (p< 0.001, OR=4.906), history of violence (p< 0.001, OR=5.443) and number of previous admissions (p< 0.001, OR=1.250) were associated with higher risk of rehospitalization. The overall accuracy of this predictor model was 83.4%.

Survival analysis with Cox regression was then conducted to examine factors that predicted earlier rehospitalization. For individuals who did not readmit but were deceased before completion of the 2 year follow up period, the date of death was taken as the date of censoring. Taking different time points in the Kaplan-Meier survival curve as plotted in Figure 2, the cumulative readmission rate of the study population was 5.2% at 1 month, 9.5% at 3 months, 15.0% at 6 months, 17.1% at 1 year, 18.8% at 1.5 year and lastly 20.9% at 2 years upon completion of the follow up period. Most of the rehospitalization occurred within the first 6 months after discharge where the slope of the curve was steepest.

Figure 2. Kaplan-Meier survival curve for graphical representation of the data on rehospitalization.

Univariate analysis by simple Cox regression was performed and the results are shown in Table 4. The significant results of subsequent multiple Cox regression survival analyses are presented in Table 5. The same four significant factors were identified in the multiple Cox regression analysis as that in the previous logistic regression analysis. Hazard ratios were calculated and Kaplan-Meier survival curves were plotted. Referral to other psychiatric disciplines upon discharge (p< 0.001, HR=0.405) correlated to a longer time to rehospitalization (Figure 3), while history of suicidal behaviors (p< 0.001, HR=3.161), history of violence (p< 0.001, HR=3.935) and number of previous psychiatric admissions (p< 0.001, HR=1.121) were predictive factors for earlier rehospitalization (Figure 4, Figure 5, Figure 6 respectively).

Figure 3. Kaplan-Meier survival curve showing decreased hazard of rehospitalization with referral to other psychiatric disciplines upon discharge.

Figure 4. Kaplan-Meier survival curve showing increased hazard of rehospitalization with history of suicidal behaviors.

Figure 5. Kaplan-Meier survival curve showing increased hazard of rehospitalization with history of violence.

Figure 6. Kaplan-Meier curve survival curve showing increased hazard of rehospitalization with greater number of previous psychiatric admissions.

Discussion

This study involved Chinese and non-Chinese elderly psychiatric patients in Hong Kong, and by comparison between the two groups, ethnicity was not identified as a significant factor. However, it should be noted that too few cases were non-Chinese and so the statistical comparison between them might not be meaningful. In comparison to other studies involving psychogeriatric patients only, most studies did not find type of residence to be a significant factor in psychiatric readmission, except 1 study²² which reported higher readmission risk in patients with little or no supervision in living arrangements following discharge. However, this study did not find any significant differences in outcome regarding rehospitalization between patients who lived alone, with others, or in placement.

The same four clinical factors were shown to be significantly associated with rehospitalization with a p value of <0.001 in both multiple logistic regression and Cox regression survival analysis, including referral to other psychiatric disciplines upon discharge, history of suicidal behaviors, history of violence and number of previous psychiatric admissions. With adequate aftercare services^6,7,29,30 by referral to other disciplines for support upon discharge, patients were more likely to comply with treatment plans and have their problems managed in outpatient settings, which reduced the need for psychiatric rehospitalization. Moreover, a study¹² had reported that patients with previous suicidal attempts were more often readmitted, and similar findings had been shown in studies that patients having violence behaviors previously were at higher risk of readmission^11,25,28,31. Psychiatric rehospitalization was often required when patients displayed risks of harming self or others. Furthermore, studies had extensively reported that patients with greater number of previous admissions were predisposed to rehospitalization^{7,8,15,20,25,32,33}. These patients might be more often rehospitalized due to suboptimal control on symptoms relating to their mental health problems and inadequate support in the community.

Concerning factors that were more specific to the elderly, 1 reviewed article²⁷ reported that elderly patients without medical comorbidity were more likely rehospitalized, however, number of chronic illnesses was not identified as a significant risk factor. Elderly patients were more likely to be hospitalized due to poor physical conditions. Sometimes psychiatric symptoms had already been treated in general wards, but readmission to general wards were not accounted in this study. Besides, having a cognitive disorder or a lower MMSE score would not affect the risk of rehospitalization. However, it was noted that over one-fourth (26.6%) of the study population did not have their MMSE scores documented, and therefore the results might differ if the MMSE scores from all study individuals were available.

Conclusion

This retrospective cohort study has provided important information regarding psychiatric rehospitalization of elderly patients. Rehospitalization was mainly affected by clinical characteristics and occurred mostly within the first 6 months after discharge. Among the significant factors for rehospitalization, history of suicidal behaviors, history of violent behaviors and greater number of previous psychiatric admissions were associated with a higher rehospitalization risk. Referral to other psychiatric disciplines upon discharge predicted a better outcome and was highly recommended for elderly patients.

Data availability

F1000Research: Dataset 1. Raw data of elderly patients discharged from psychiatric wards within the study period, 10.5256/f1000research.7135.d103399³⁶