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Sleep disruptions and mental health of caregivers of persons with disability in Australia
Lawrence T. Lam
Abstract
Objective: This study aims to investigate the association between sleep disruption and the general mental health of caregivers of disabled people in Australia.
Methods: It utilises data obtained from a national health survey of a stratified random sample from the total population of people with disability, aged 60 years or older and carers of people with disability. Sleep disruptions were assessed by responses to a direct question during a personal structured interview. General mental health of caregivers was assessed using the SF-12v2 Health Survey to obtain the mental health summary scores. Data were analysed using multinominal logistic regression to cater for the multiple classifications of the outcome.
Results: After adjusting for potential confounding factors, results suggested a significant association between sleep disruptions and poor mental health among caregivers. Those who were frequently disrupted in their sleep were 2.5 times more likely to experience severely poor mental health (OR:2.54, 95%C.I:=1.41, 4.55) when compared to those whose sleep was not interrupted at all. There was no significant association between occasional disruptions and poor mental health after adjusting for potential confounders.
Conclusions: Results suggested that sleep disruptions can be considered as a potential risk factor for severely poor mental health among caregivers.
Introduction
The impact of caring for a chronically ill person or people with disability on the physical and mental health of the caregivers has long been recognised and studied (Baumgarten, 1989; Pinquart and Sorensen, 2003; Vitaliano et al., 2003; Pinquart and Sorensen, 2007; Pruchno, 1990; Saunders, 2003; Prachakul and Grant, 2003; Savage and Bailey, 2004). On the whole they were significantly depressed, experienced more stress, and had lower self-efficacy than non-caregivers (Pinquart and Sorensen, 2003).
Among many caregiving-related health issues, sleep problems have been reported in many studies (Matsuda et al., 1997; Wilcox and Kind, 1999; Flaskerud et al., 2000; McKibbin et al., 2005; Meltzer and Mindell, 2006; Tsukasaki et al., 2006; Creese et al., 2007). These problems include nighttime or early morning waking, difficulties in sleep onset, poor sleep quality, less slow-wave sleep, insomnia, and most commonly, sleep disruptions (Matsuda et al., 1997; Wilcox and Kind, 1999; Flaskerud et al., 2000; Tsukasaki et al., 2006).
Sleep disruptions as a risk factor for poor mental health among caregivers has been suggested recently. Two studies reported an association between sleep problems and depression among caregivers of cancer patients and older wives of patients with Alzheimer's disease (Carter and Chang, 2000; Willette-Murphy et al., 2006). However, both were small scale studies with patients of older ages. For the relationship between sleep disruption and the general mental health of caregivers of disabled people of all-ages due to chronic illness no report has been found so far.
The aim of this study is to examine the association between sleep disruptions and the general mental health of caregivers of people with disability due to various types of chronic illness across all- ages utilising data obtained from a population-based health survey.
Methods
This study analysed data obtained from the survey of disability, ageing and carers (SDAC) conducted by the Australian Bureau of Statistics (ABS) in 2003. Data were obtained from the ABS with institutional approval for using the data set for the study. Details of the survey methodologies were reported in the information paper published by the ABS (Australian Bureau of Statistics, 2003a; Australian Bureau of Statistics, 2003b). The 2003 survey was conducted in the period between June to November including both urban and rural areas in all states and territories of Australia except those living in remote and sparsely habited areas. Included in the survey were people who lived in both private and non-private dwellings, for example boarding houses, as well as care-accommodations such as retirement villages, but excluded prisons and correctional facilities. This study focused on caregivers in private dwellings only.
The survey was conducted using randomised multistage sampling techniques, with the type of dwellings used to select the sample. Details of the sample design and selection procedures were presented by the ABS (Australian Bureau of Statistics, 2003a). In total, the sample contained 14,019 private dwellings with 41,233 records of individual respondents including people with disability, people aged 60 and over, and caregivers of disabled people. For caregivers, apart from demographics, other information was also collected on the characteristics of the main recipient of care, other factors related to the caring of a disabled person, and an assessment on the general health status particularly the mental health status of each caregiver. Main recipient characteristics included chronic condition causing the major disability, number of recipients receiving care from the caregiver duration of care provided by the primary caregiver, relationship of caregiver to the recipient, hours of care provided per week, and disability status of the recipient. Other factors related to caring included whether the caregiver need to leave work due to caring, whether the relationship with spouse/partner was affected due to caring, whether the financial situation was affected, whether the need of respite was satisfied, and whether caregivers experienced any sleep disruptions due to caring for the main recipient.
Of particular interest in this study was the relationship between sleep disruption and the general mental health status of these caregivers. Information on sleep disruption was elicited from responses to the question whether the primary carer's sleep was interrupted due to their caring role. Responses to this question were discrete answers which were categorised into frequently, occasionally, and not disrupted at all.
In terms of the general mental health status of the primary caregivers, it was assessed using the SF-12v2TM Health Survey (Ware et al., 2005). Standardised scores were calculated from responses to the survey and were aggregated into two summary scores, the physical and mental health summaries. These two summary scores were then transformed using a norm-based transformation method to produce the t-score with a mean of 50 and a standard deviation of 10 with high scores indicating good general health status (Ware et al., 2005). Due to the highly skewed distribution of the t-scores and for the ease of analysis, the transformed mental health summary scores were classified into four categories ranging from severely poor, mildly/moderately poor, good, and excellent using the 25th, 50th, and 75th percentile of the norm for healthy adults without chronic conditions as cut-off points.
Data were analysed using the Stata statistical software program (StataCorp, 2005). Since all variables included in the study were categorical by nature, they were analysed accordingly. Bivariate analyses were conducted to examine unadjusted associations between all variables of interest including sleep disruptions and caregivers' mental health status. Chi-squared tests were applied to examine these bivariate relationships. Due to the multiple categories of the outcome variable, data were analysed using Multinominal Logistic Regression modelling using the excellent mental health group as the referent group. Hence, the unadjusted Odds Ratio (OR) and the corresponding 95% confident intervals (95%C.I.) for each category of mental health status were calculated using multinominal logistic regression procedures. The adjusted Odds Ratios were also calculated with adjustment to potential confounding factors identified in the bivariate analyses were then included in the multinominal logistic regression analysis. For the inclusion of any variable in the regression model, the criteria of a bivariate association with p<0.20 or any known risk factor for ill mental health was used. Presentations for all p values were two sided.
Results
A total of 687 primary caregivers of disabled persons residing in private dwellings were surveyed in this national study. The demographic characteristics of caregivers were summarised in Table 1. In terms of the characteristics of the main recipient of care, the majority had disabilities due to a chronic physical condition (n=550, 80.1%), with the remaining having a mental or behavioural disorder. Slightly more than half (n=398, 57.9%) of these recipients of care were classified as having profound disability, and 34.2% (n=235) were severely disabled. Most caregivers provided care only to one recipient (n=547, 79.6%) with one third (n=238, 35.4%) provided care for more than 10 years, 183 (n=27.2%) between 5 and 9 years, and 37.4% (n=252) less than 5 years. Nearly half (n=313, 49.1%) provided care for more than 40 hours per week, 20% between 20 and 39 hours (n=131), and 30.4% (n=194) less than 20 hours weekly.
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Slightly more than a quarter (n=149, 21.7%) of these caregivers left their work for the reason of providing care. About a quarter (n=131, 20.4%) reported that their relationship with their spouse or partner was adversely affected due to their caring role. Nearly half (n=307, 49.0%) indicated that their financial situation was worsened as a result of caring for a disabled person, and 17.8% (n=130) had unsatisfied needs of respite. In terms of the exposure variable, namely sleep disruptions, 167 (26.1%) reported that their sleep was frequently interrupted due to their caring role, 170 (26.5%) were occasionally interrupted, and 304 (47.4%) were not disrupted at all. For the general mental health status of these caregivers, using the above-mentioned cut-off, 261 (37.9%) were classified as severely poor, 149 (21.7%) were mildly/moderately poor, 14.6% (n=100) was considered as good, and 25.8% (n=177) were classified as having the best mental health.
The bivariate associations between sleep disruptions, caregivers' demographics, characteristics of the main recipient, factors related to the caring role, and general mental health status of caregivers were examined. Results were also presented in Table 1. As shown, sleep disruptions, relationship with spouse/partner, financial situation, and unsatisfied need of respite were associated with the general mental health status of caregivers. The unadjusted associations among all these variables were highly significant (p<0.001). Age of caregivers and the chronic condition causing major disability were also associated with caregivers' mental health at a 5% significant level but not at 1%. Hence, these variables were included in the multinominal logistic regression analyses to be adjusted for their effect on the relationship between sleep disruption and caregivers' general mental health. Additionally, other variables such as sex, area of residence, number of recipients under care, and weekly hours of care were also included. The unadjusted ORs for mental health status of different levels of sleep disruption were calculated and summarised in Table 2. As shown, the odds for severely poor mental health were significantly increased for those caregivers whose sleep had been frequently and occasionally disrupted when compared with those whose sleep was not disrupted at all (Table 2). There were no significant associations between sleep disruption and other levels of mental health status.
Multinominal logistic regression analyses were performed on the data with potential confounding factors identified in the bivariate analyses included. Models including interaction terms between these variables and sleep disruption were also fitted. The results indicated that none of these interaction terms were significant, suggesting that these variables were potential confounding factors and not effect-modifiers. The adjusted results obtained from the final multinominal logistic regression model were also presented in Table 2. After adjusting for potential confounding factors including age, sex, disability status, relationship with the recipient, financial situation, relationship with spouse/partner, and need of respite, the association with frequent sleep disruptions and severely poor mental health remained significant. There was a two and half times increase in the odds of severely poor mental health (OR:2.54, 95%C.I.:1.41-4.55) for those caregivers whose sleep was frequently disrupted due to his/her caring role when compared with those whose sleep was not disrupted at all. Contrary to the unadjusted results, the association between occasional sleep disruption and poor mental health became insignificant after adjusting for potential confounding factors.
Discussion
The results obtained suggest that sleep disruption is detrimental to the general mental health of caregivers. Caregivers whose sleep is frequently disrupted are 2.5 times more likely to suffer from poor mental health as compared to those who are not disrupted. Since none of the interaction terms between independent variables and sleep disruption were significant, sleep disruption can be considered as an independent risk factor for poor mental health of caregivers. The results are consistent with two similar previous studies, although no specific risk estimates were obtainable from these reports (Carter and Chang, 2000; Willette-Murphy et al., 2006).
A possible explanation for the association between frequent sleep disruption and poor mental health lies in the characteristic of sleep, particularly the phase of sleep known as Rapid Eye Movement sleep (REMS). During REMS the brain activity is quite similar to that at a waking stage and neurons in the brain steam are particularly active. It has been established that REMS is negatively associated with depression in humans where a deprivation in REMS exhibits an antidepressive effect and most antidepressant medications suppress REMS (Thase, 2006). This relationship between REMS and depression is possibly attributable to a neuroanatomical and neurochemical processes (Germain et al., 2004). Sleep disruption might interrupt the REMS and shorten the duration of REMS during a normal sleep. However, as REMS is deprived the human body will compensate with a prolonged REMS which is known as a REMS rebound. Frequent sleep disruptions may effect more frequent REMS rebound in those caregivers who are frequently deprived of sleep. Hence a negative effect on the mental health of these caregivers. Other explanations are also possible. For example, the mood of caregivers will be affected by sheer weariness and annoyance that their sleep is frequently interrupted in the middle of the night. Lack of energy due to not having a good rest at night resulting from a lengthy accumulated sleep debt may also affect the mental health of these caregivers.
The results obtained from this study have a direct implication on the provision of support to caregivers. Sleep disruption is a potentially modifiable risk factor. In terms of respite for caregivers, they are normally provided as a short term measure and for a short period of time usually during the day. The results of this study suggest long-term caregivers require more support during night-time so that they can have a reprieve from their duties, at least temporarily so that they can recover their sleep debt.
As in all studies, there are strengths and weaknesses in this study. This study utilised data collected from a population-based national survey. Participants of the survey were randomly selected from the total target population using a validated and statistically proven methodology. This has provided confidence for the representativeness of the sample as well as the generalisation of the results obtained.
Some potential limitations also have been identified. First, there may be report bias in the outcome variable due to self-reporting although the standardised SF-12v2 was used. Moreover, SF-12 is only a measure of general mental health, not a specific assessment of a particular mental health problem such as depression. It is well known that depression is associated with sleep problems, particular insomnia. Hence it could be considered as a potential confounding factor in the relationship between sleep disruption and ill mental health. Unfortunately, depression was not assessed in this study, and thus not adjusted for in the analysis. Second, recall bias may occur in the assessment of sleep disruptions also due to self-reporting. There may be over-reporting due to subjective feelings towards the interruption. Finally, the strength of evidence provided by a study with a cross-sectional design is insufficient to draw any causal inference (Rothman and Greenland, 1998). In order to confirm the relationship between sleep disruption and poor mental health, a study of better design such as a prospective study should be conducted.
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Contributor:
A/Prof. Lawrence T. Lam
Head of Epidemiology and Medical Statistics
Deputy Chair Population and Public Health Domain
School of Medicine Sydney
The University of Notre Dame Australia
Darlinghurst Campus
160 Oxford Street
Darlinghurst NSW 2010
PO Box 944, Broadway, NSW 2007
Email: llam@nd.edu.au
Author Biography:
Lawrence T. Lam is trained as an Epidemiologist and Biostatistician and has been involving in both clinical work and research in the area of trauma care, injury prevention, and rehabilitation. He holds a position as the Head of Epidemiology and Medical Statistics, School of Medicine Sydney of the University of Notre Dame Australia. He is also the Scientific Director of the Centre for Trauma Care, Prevention, Education, and Research at the Royal Alexandra Hospital for Children, Sydney, Australia as well as a Senior Lecturer in the Faulty of Medicine, The Sydney University. One of his current projects is the effects of prescribed anaerobic exercise on the recovery from traumatic head injuries among children and adolescents.
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