The impact of depression, seizure variables and locus of control on health related quality of life in a community dwelling sample of older adults
Article Outline
- Abstract
- 1. Methods
- 2. Measures
- 3. Results
- 4. Discussion
- 5. Conclusion
- Conflict of interest
- Acknowledgements
- References
- Copyright
Abstract
Few studies have examined the impact of epilepsy on the quality of life of older people, although epilepsy is one of the most common neurological disorders of old age. This study investigated the association of depression, seizure type and frequency and locus of control on health related quality of life in community dwelling adults aged over 60 years. Sixty-four participants were administered a clinical diagnostic interview to assess depression and dysthymia, and completed measures of HRQOL (QOLIE-31), locus of control and provided information on seizure variables. Depression, dysthymia and more frequent seizures were important predictors of HRQOL, accounting for 63% of the variance, with dysthymia the strongest individual predictor of impaired HRQOL. This study has highlighted the negative consequences of depression, dysthymia and seizure frequency on HRQOL for older people with epilepsy. Importantly, these results indicate that rather than major depression, it is the more chronic symptoms of dysthymia that are most disruptive of HRQOL. Seizure frequency, but not seizure type, was also associated with reduced HRQOL. The results of this study suggest that clinical treatment in late adulthood should address seizure control while concurrently focusing on the management of depressive symptomatology to improve overall HRQOL.
Keywords: Older adults, HRQOL, Depression, Seizure variables, Locus of control
Epidemiological studies have described epilepsy as a common neurological disorder of older age and one which represents a considerable health issue.1, 2 Depressive disorders have a significant impact on the health related quality of life (HRQOL) of people with epilepsy: the adverse effects of depression on HRQOL in epilepsy have been strongly supported in a number of studies among adult populations.3, 4, 5, 6 Risk factors proposed to have an association with psychopathology in people with epilepsy include seizure related variables such as seizure type and frequency7, 8 and psychosocial factors such as adjustment to epilepsy, fear of seizures, financial stress, social support9 and locus of control.10 Older adults may be particularly vulnerable to the psychological impact of epilepsy: the functional limitations that often accompany ageing may be exacerbated by the limitations imposed by epilepsy, with subsequent restrictions to independent living.
It has been estimated that depressive disorders are frequently associated with uncontrolled seizures, with a reported prevalence of up to 50%.7, 11 However, evidence of the relationship between seizure frequency and depression is far from conclusive and a number of researchers have reported no significant differences in the prevalence of depression between those with uncontrolled seizures and participants whose seizures were controlled.12, 13 Clinically, the gold standard of treatment has focussed on complete seizure remission and a current review of psychiatric co-morbidity in epilepsy14 has asserted that stringent seizure control was essential for optimal clinical outcome.
Rather than seizure frequency, a number of researchers have suggested that it may be type of seizure which is implicated with depression in epilepsy.15, 16 The relationship between type of seizure and depression has been the subject of considerable investigation, with some studies suggesting that up to 62% of people with uncontrolled complex partial seizures have a history of depression.17 One reason for the postulated association with partial (i.e., non-convulsive) seizures may be that depression can be relieved by tonic–clonic seizures which mimic the effects of electro convulsive therapy.18 The role of seizure related variables is uncertain, however, with neither seizure type nor aetiology being consistently associated with depression.8
There is a large general psychological literature that has addressed the relationship between external locus of control, depression and subsequent learned helplessness, however, the loss of control that is characteristic of epilepsy has not been well studied in this context.10 An internal locus of control is reflected in the belief that one has control over important events and experiences in life, whereas an external locus of control relies on luck, others or powerful forces being in control of one's fate.8 Recent studies in younger adults have indicated that patients with uncontrolled seizures were significantly more likely to have strong perceptions of external locus of control19 and low HRQOL.20
The impact of a diagnosis of epilepsy in late adulthood may have important ramifications: at a time of life when many people are anticipating retirement activities, a diagnosis of epilepsy and the concomitant limitations it imposes may be difficult to accept. The myths and misunderstandings regarding epilepsy commonly held by this generation21 may impact on HRQOL and increase the risk of depression.
The reviewed studies suggest that there are relationships among HRQOL, depression, seizure related variables and locus of control; however, these relationships are not consistent and warrant further research. Furthermore, even in those studies which utilised diagnostic criteria to measure depression, very few have concurrently examined other factors, such as seizure variables and HRQOL and none have examined these variables in an older population.
Thus, the aim of this study was to examine the association among HRQOL, depression, seizure type and frequency and locus of control in community dwelling older people.
1. Methods
1.1. Participants and procedure
Participants were 64 community dwelling older adults (28 males and 36 females) living in Queensland, Australia, with a confirmed diagnosis of epilepsy from a general medical practitioner, neurologist, neurosurgeon or geriatrician. Recruitment was initially by mailout of flyers to members of a state epilepsy support organisation and to specialist medical practitioners and public hospitals, including those with epilepsy clinics. A further recruitment wave 2 months later was facilitated through an Australian national epilepsy support organisation. To maintain member confidentiality, study flyers were provided to the epilepsy support organisations and sent by them to their members, so total number of members who received the flyers is not known. The first recruitment round garnered 39 participants and the second gathered an additional 25 participants. All participants had experienced formal testing to confirm the diagnosis of epilepsy, either by EEG, MRI or CT scan. Seizure type was described in accordance with the ILAE classification scheme22 and was based on both patient report and perusal of patient provided medical records, which were examined to confirm diagnosis and test results.
Inclusion in the study required that the person be aged 60 or older, have a diagnosis of epilepsy from a medical practitioner, have a Mini Mental State Examination (MMSE)23 score >24 indicating no cognitive impairment, be English speaking and be able to provide information on their physical and medical status.
This study was approved by the human ethics committee of the University of Queensland and all participants provided informed consent for participation.
2. Measures
Quality of Life in Epilepsy (QOLIE-31)27 is a 31 item, self-administered questionnaire specifically designed to measure quality of life of people with epilepsy and which was derived from the QOLIE-89.28 The QOLIE-31 has seven of the 17 QOLIE-89 subscales. Responses are summed to supply subscale scores and a total score, with higher scores indicative of better functioning. The QOLIE-31 has demonstrated good psychometric properties with internal consistency reported as Cronbach's α
=0.85 and test–retest reliability of r=0.85.27 Reliability analysis of the QOLIE-31 for this study revealed an excellent Cronbach's α of 0.95. The subscale QOLIE overall score was used in analyses as it is a summary score which is derived by weighting and summing all the QOLIE-31 scale scores. The overall score subscale has a test–retest reliability of 0.89 and Cronbach's α of 0.93.27
Composite International Diagnostic Interview (CIDI)-Auto24 is a computerised, structured diagnostic interview for the assessment of mental disorders which provides diagnoses according to the accepted definitions of both the International Classification of Diseases, 10th Edition (ICD-10) and the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV). During the CIDI-Auto interview, participants are asked a series of questions about symptoms of psychiatric disorders. Positive responses to some of the symptom questions are followed by questions from the Probe Flow Chart which determine whether the symptom is a possible psychiatric symptom that is not due to medication, drugs or alcohol or to physical illness or injury. If sufficient symptoms are indicated and these symptoms occur in a pattern that suggests a diagnosis may be present, participants are asked about the onset and recency of the particular symptoms they have described. For the purposes of this study, the interviewer requested information from participants on depressive and dysthymic symptomatology resulting in two variables CIDI Depression and CIDI Dysthymia. Scoring is on a scale of 0=indeterminate diagnosis to 5=all diagnostic criteria met. The CIDI-Auto has excellent inter-rater reliability (kappa=1.00) and test–retest reliability (1 month) of 0.55–0.83,25 depending on diagnosis of disorder, and also demonstrates acceptable validity with an average kappa coefficient of 0.40.26
2.1. Seizure frequency
In accordance with earlier research,30 participants were asked to categorise their seizures as occurring (1) more than once per week, (2) more than once per month, (3) more than once per year or (4) none in the past 12 months.
2.2. Seizure type
For the regression analysis, seizure type was dichotomised as either partial or generalised onset.
Internal/External Control of Reinforcement Scale29 is a forced choice, self-report inventory that determines the extent to which a participant believes that reinforcement is contingent upon his/her behaviour (internal) as opposed to directed by external forces (external). This scale has been widely utilised and has demonstrated satisfactory reliability and validity, although some concerns have been raised regarding its factor structure and correlation with social desirability measures. Higher scores indicate a more external locus of control.
3. Results
All analyses were performed using SPSS version 12 for Windows.31
Demographic and epilepsy related characteristics of the group are presented in Table 1.
Table 1. Demographic and epilepsy related characteristics of the group (n=64).
| Male | 28 (44%) |
| Female | 36 (56%) |
| Mean age | 67.59 (7.42) |
| Marital status | |
| Married/deFacto | 32 (50%) |
| Widowed/divorced | 19 (30%) |
| Single | 13 (20%) |
| Education | |
| Tertiary | 19 (30%) |
| High school | 22 (34%) |
| Primary school | 17 (27%) |
| Trade or other qualification | 6 (9%) |
| Employment | |
| Full-time | 12 (19%) |
| Part-time | 3 (5%) |
| Home duties | 14 (22%) |
| Retired | 35 (54%) |
| Seizure type | |
| Tonic clonic | 40 (62.5%) |
| Simple partial | 17 (26.5%) |
| Complex partial | 26 (40.6%) |
| Absence | 6 (9%) |
| >1 seizure type | 20 (31.2%) |
| Seizure frequency | |
| >1 per week | 3 (4.7%) |
| >1 per month | 15 (23.4%) |
| >1 per year | 23 (35.9%) |
| None in past year | 23 (35.9%) |
| Type of medication | |
| Phenytoin | 27 (42%) |
| Valproate | 18 (28%) |
| Lamotrigine | 14 (22%) |
| Carbamazapine | 16 (25%) |
| Topiramate | 6 (9.4%) |
| Primidone | 8 (12.5%) |
| Rivotril | 2 (3%) |
| Neurontin | 1 (1.5%) |
| Tiagabine | 1 (1.5%) |
| Clonazepam | 2 (3%) |
| Barbiturate | 3 (4.7%) |
| Number of medications | |
| None | 2 (3.1%) |
| 1 | 33 (51.6%) |
| 2 | 22 (34.4%) |
| 3 | 7 (10.9%) |
Means and standard deviations for CIDI depression, CIDI dysthymia, locus of control and all scales of the QOLIE-31 are presented in Table 2, together with general epilepsy population scores for the QOLIE-31 that have been reported in other studies.27 Preliminary analyses indicated that each of the QOLIE-31 sub scales was significantly negatively correlated with the two measures of depression, however, only the QOLIE overall score is reported. Significant negative correlations were found between the QOLIE overall score and CIDI depression (r=−0.587, p<0.01), CIDI dysthymia (r=−0.679, p<0.01) and seizure frequency (>1 seizure per week) (r=−0.354, p<0.01).
Table 2. Summary of mean scores (standard deviations) obtained for QOLIE-31, CIDI and locus of control for the group (n=64) compared with general epilepsy population scores.
| General epilepsy population scores [27] | ||
|---|---|---|
| QOLIE-31 | ||
| Overall QOL | 52.89 (23.12) | 67 (18) |
| Emotional well-being | 52.97 (19.95) | 67 (19) |
| Energy/fatigue | 49.30 (17.86) | 55 (21) |
| Cognitive function | 53.39 (22.41) | 60 (23) |
| Social function | 53.56 (23.90) | 67 (27) |
| Seizure worry | 50.55 (33.76) | 58 (26) |
| Medication effects | 50.36 (25.34) | 55 (31) |
| CIDI depression | 1.64 (1.51) | |
| CIDI dysthymia | 2.50 (1.94) | |
| Locus of control | 13.28 (4.08) | |
To investigate the relationships among HRQOL, depression, seizure frequency, seizure type and locus of control, a standard multiple regression was performed using the QOLIE-31 overall score as the criterion variable. The independent variables were CIDI depression and CIDI dysthymia, seizure frequency, seizure type and locus of control. Both of the CIDI measures were used as the depression predictors to obtain an accurate clinical assessment of symptoms of both depression and dysthymia. Table 3 displays the unstandardized regression coefficients (B), their standard error and intercept, the standardized regression coefficients (β), the semipartial correlations (sr2), R2 and adjusted R2. R for regression on the HRQOL measure was significantly different from zero, F (8, 55)=14.41, p<0.001.
Table 3. Standard multiple regression of CIDI depression, CIDI dysthymia, seizure frequency, seizure type and locus of control as predictors of HRQOL (n=64).
| B | SEB | β | sr2 | |
|---|---|---|---|---|
| CIDI depression | −3.04* | 1.30 | −0.231 | 0.03 |
| CIDI dysthymia | −4.78*** | 0.93 | −0.469 | 0.15 |
| >1 seizure week | −29.45** | 8.12 | −0.317 | 0.08 |
| >1 seizure month | −14.24** | 4.52 | −0.307 | 0.06 |
| >1 seizure year | −11.95** | 3.90 | −0.292 | 0.05 |
| Seizure type | −0.915 | 3.17 | −0.023 | 0.000 |
| Locus of control | 0.302 | 0.425 | 0.067 | 0.003 |
| Intercept=77.73 | R2=0.68 | Adjusted R2=0.63 | R=0.82** | |
*p |
**p |
***p |
In the HRQOL regression, three of the independent variables contributed significantly to prediction of HRQOL, CIDI depression (sr2=0.03), CIDI dysthymia (sr2=0.15) and seizure frequency: more than one per week (sr2=0.08), more than one per month (sr2=0.06) and more than one per year (sr2=0.05). Higher rates of depression, elevated dysthymia, and greater frequency of seizures uniquely contributed to the overall prediction of reduced health related quality of life. Overall, the predictors of CIDI depression, CIDI dysthymia, seizure frequency, seizure type and locus of control together accounted for 63% of the variability in health related quality of life.
A one-way analysis of variance was conducted to further explore the impact of seizure frequency on depression and dysthymia. Seizure frequency was divided into four groups: group 1, >1 per week, group 2, >1 per month, group 3, >1 per year, group 4, none in past 12 months. There was a statistically significant difference at the p<0.01 level in CIDI Depression scores for seizure frequency (F (3, 63)=4.82, p<0.01), however, CIDI dysthymia did not reach significance (F (3, 63)=2.70, p=0.054). The effect size calculated using η2 was 0.19. Post hoc comparisons using the Tukey HSD test indicated that the mean score for group 4 (M=1.00, SD=0.522) was significantly different from group 1 (M=3.67, SD=2.31) and from group 3 (M=2.13, SD=1.69). Seizures that were more frequent than one per week or one per year were thus associated with more depressive symptomatology, although seizure frequency of more than one per month did not reach significance.
4. Discussion
Consistent with prior studies involving younger adults, the current study found that important predictors of HRQOL in older people with epilepsy were depression and dysthymia3, 5, 32 and more frequent seizures.7 Older persons in this study who were more depressed and dysthymic and who had more frequent seizures reported a significantly lower HRQOL. In particular, the presence of dysthymic symptoms in older persons with epilepsy were the strongest predictors of impaired HRQOL. While the impact of depression on HRQOL in epilepsy has been strongly supported in a number of prior studies,3, 6, 32 most investigators have suggested that it is severe depression, or major depressive disorder, that is the most disruptive of HRQOL. These findings lend further support to the importance of clinical diagnosis in research: most of the studies which have linked a greater severity of depression with reduced HRQOL have relied solely on self-report inventories3, 4, 5, 6 that do not differentiate clearly between the symptoms of major depressive disorder and the more chronic symptoms of dysthymia.
Seizure frequency exerted a substantial impact on HRQOL, with more frequent seizures being a significant predictor of impaired HRQOL. Additional analyses revealed that participants with frequent seizures (more than 1 per week) were significantly more depressed than those with few or no seizures. These results are consistent with earlier studies which have reported a clear relationship between seizure frequency and psychological well-being.11, 14 The relationship between seizure frequency and dysthymia did not reach significance, however, implying that it is the more severe symptoms of major depressive disorder that are associated with greater frequency of seizures. It would appear therefore, that seizure control in an older population is an important aspect of clinical management and achievement of seizure reduction should have a positive effect on depressive symptoms and health related quality of life. Contrary to expectations, partial seizure type and external locus of control were not significant indicators of impaired HRQOL. Although a number of authors have stressed the relationship between seizures of partial origin and increased depression,15, 17 others have reported no relationship between seizure type and measures of affect.8, 33 Results from the current study demonstrate no association between seizure type and depression, dysthymia or HRQOL. Thus, while more frequent seizures may impair quality of life within an older group, it would appear that whether the seizures originate from a focal point or are generalised makes no difference to the well being of older persons with epilepsy.
Prior research on the concept of locus of control in epilepsy has been very limited and conflicting,10, 19, 20 although the general psychological literature on the topic is large. However, this study was unable to support the importance of locus of control as a variable of interest in older people with epilepsy. This may reflect the choice of a generic rather than an epilepsy specific measure for this variable. A number of measures of locus of control have been used previously in epilepsy populations, including the Internal/External Control of Reinforcement scale29 which was used for this study. However, future researchers may consider the use of an alternative measure of locus of control, for example the epilepsy specific Mastery scale developed by Wagner et al.34
There are a number of limitations to this study and results should be interpreted with caution. Firstly, with the exception of the diagnostic interview and confirmation of seizure related factors with medical report, all measures are self-report. Because of the lack of independent confirmation, with biological measures, of anti-epileptic drug use, consideration of medication effects did not form part of the analyses and future studies should address this issue. As with all studies which rely on self selection, sample selection may be biased and no causality can be determined due to the cross-sectional nature of the design.
5. Conclusion
There is a paucity of research specifically on older, community dwelling people with epilepsy and this study provides key information on some factors which impact on HRQOL in this group. In particular, this study highlights the importance of dysthymia and seizure frequency as variables affecting HRQOL in late adulthood epilepsy. Future research could usefully address some of the limitations of this study; for instance, random sampling of an older population with epilepsy would remove an important potential source of bias.
Conflict of interest
The authors have no conflicts of interest related to the content of this article.
Acknowledgements
The authors acknowledge the assistance of Epilepsy Queensland Inc. and Epilepsy Action (Australia) for their assistance in promoting this study to their members.
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PII: S1059-1311(10)00051-8
doi:10.1016/j.seizure.2010.02.008
© 2010 British Epilepsy Association. Published by Elsevier Inc. All rights reserved.
