Health Economics Research Centre
Centre for Risk and Insurance Studies, Nottingham University Business School
Health Economics Research Centre, University of Oxford
Department of Psychiatry, University of Oxford
Department of Medical Ethics, University of Oxford
Correspondence: Jane L. Wolstenholme, Health Economic Research Centre, JHS, University of Oxford, Old Road, Headington, Oxford OX3 7LF
Declaration of interest The original study was funded by the Medical Research Council and the economic re-analysis by an unrestricted educational grant from Novartis.
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Aims To explore the factors affecting time to institutionalisation and estimate the relationship between the costs of care and disease progression.
Method Retrospective analysis of a longitudinal data-set for a cohort of 100 patients diagnosed with Alzheimer's disease or vascular dementia.
Results Changes in both Mini-Mental State Examination (MMSE) and Barthel scores have independent and significant marginal effects on costs. Each one-point decline in the MMSE score is associated with a £56 increase in the four-monthly costs, whereas each one-point fall in the Barthel index is associated with a £586 increase in costs.
Conclusions It may be inappropriate for economic models of disease progression in dementia to be based solely on measures of cognitive change. MMSE and the Barthel index are independent significant predictors of time to institutionalisation and cost of care, but changes in the Barthel index are particularly important in predicting costs outside institutional care.
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
The objectives of this study were to explore the factors affecting time to institutionalisation and to estimate the relationship between the costs of care and disease progression, measured by cognitive function, behavioural scores and activities of daily living (ADL), using retrospective analysis of a longitudinal data-set for a cohort of 100 patients diagnosed with Alzheimer's disease and/or vascular dementia.
![]() |
METHOD |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
Out of the 100 subjects interviewed at study entry, six withdrew from the study and three were still alive at August 1999. The mean age at study entry was 78 years (s.d.=7.0) but, given that all subjects had already been diagnosed with dementia when recruited to the study, the mean age at onset was 73 years (s.d.=7.5).
Resource use and unit costs
A coding frame was designed and information on resource utilisation was
extracted from each subject's four-monthly assessment records on the
following: number and duration of acute hospitalisations and respite care;
number of out-patient visits, day care and home attendances by district
nurses, CPNs, home helps or other care assistants; and number of visits by or
to the GP or practice nurse. Details on the use of special aids and
adaptations such as wheelchairs, bath/bed hoists, incontinence pads and sheets
and any special dietary requirements were also recorded. An important aspect
of care for a patient with dementia is where the care took place. At each
interview it was noted whether the subject still resided at home or had been
institutionalised. The point at which subjects were rated as being
institutionalised was taken as the time when they were admitted
to a hospital ward or a nursing home for permanent care
(Hope et al, 1998).
Unit costs were attached to these cost-generating events (see Table 1), enabling an estimation of patient-specific costs of dementia by the four-month period from study entry to death or censor point. Where appropriate, the unit costs of all hospital admissions and out-patient visits were based on information from financial returns for the specified trusts. The unit costs of home attendances by district nurses, CPNs, home helps or other care assistants and visits by or to the GP or practice nurse were taken from previously published sources (Netten et al, 1998, 1999). The market price of equipment, consumables and non-structural home modifications was used. Residential and nursing home care costs were based on actual costs of care in each facility. All unit costs were updated to 1998 prices and are reported in UK £ sterling.
|
Indicators of disease progression
As part of the original cohort study, data were collected every 4 months on
the cognitive, behavioural and functional abilities of the patients using the
Mini-Mental State Examination (MMSE;
Folstein et al, 1975) and the
Present Behavioural Examination (PBE; Hope
& Fairburn, 1992). The MMSE score ranges from 0 to 30, with a
score of zero indicating the severest loss of cognitive function. The
behavioural and functional data collected using the PBE questionnaire were
transcribed onto the Barthel ADL index
(Wade & Collin, 1988). For
the purpose of this paper it was felt that it was better to transcribe the
data collected using the PBE to the Barthel index owing to the complexity of
the PBE, the greater familiarity with the Barthel index, to enable comparisons
with other studies and the fact that the Barthel index is widely used in
long-term care insurance. This index measures functional capabilities such as
bowel and bladder continence, toilet use, bathing, feeding, grooming,
dressing, mobility and ability to cope with stairs. The score ranges from 0 to
20, again with zero indicating the greatest impairment. The transformed data
were believed to have good validity, because the information required to
complete the Barthel index was much less than the information collected by the
PBE. Two other variables measuring degrees of aggressive behaviour and
wakefulness, which are dimensions of behaviour not included in the MMSE or
Barthel index, were obtained from the PBE questionnaire and included in the
analysis.
Data analysis
The data were entered into SPSS version 10, and primary analysis of the
total cost per patient over the whole period was conducted. One-way analysis
of variance was used to explore the difference in costs between disease
severity scores for the MMSE and Barthel index. For the purpose of further
analysis using longitudinal and survival and analysis techniques, the data
were transferred to another statistical software package: Stata version 6.
Variations in the measured aggregate cost per four-month period and the impact of covariates such as age, measures of disease progression and care regime were explored using a fixed-effects regression model (Greene, 1999). In this model, consistent patient-specific differences in costs that are not explained by the covariates are estimated through the regression constants (the fixed effects) rather than absorbed into the residual. The second analytical technique used in this paper to explore the relationship between time to institutionalisation and covariates such as age, gender, disease progression and domestic circumstances is the Cox proportional hazards regression (Cox & Oakes, 1984). This technique is used to analyse time-to-event data. In this paper it explores the impact of the (potentially time-varying) covariates described above on the hazard of institutionalisation.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
The relationship between the cognitive, functional and behavioural capabilities of the patients and the costs incurred caring for the patients was explored. The MMSE and Barthel scores were separated into disease severity classifications that had been used previously in studies exploring the relationship between cost of disease and disease progression (Hux et al, 1998; Porsdal & Boysen, 1999). The MMSE score was divided into severe (<10), moderate (10-14), mild to moderate (15-20) and mild (>20) and the Barthel score into severe (0-9), moderate (10-14), slight (15-19) and no disability (20). Figure 3 shows how the average annual cost of care per patient increases significantly with severity of dementia. Focusing on cognition as measured by the MMSE, the annual cost per patient was estimated to be £8312 (s.d.=5602) for mild disease, £11 643 (s.d.=7808) for mild to moderate disease, £15 681 (s.d.=9509) for moderate disease and £22 267 (s.d.=14 507) for severe disease (one-way analysis of variance: F=23.17, P<0.001). On the Barthel ADL scale, average annual care cost per patient ranged from £8086 (s.d.=3556) for no disability, £12 752 (s.d.=7632) for slight disability, £23 240 (s.d.=15 638) for moderate disability to £23 516 (s.d.=13 253) for severe disability (one-way analysis of variance: F=38.72, P<0.001). The cost information reported here is on an annual basis. Elsewhere in this paper the costs are based on a four-month period.
|
Cost per period
Given that the data were collected on a longitudinal basis, we explored the
impact of the different variables on the total cost of care over time using
longitudinal data methods. A list of the variables used in the analyses and
their descriptions is displayed in Table
2. The results from the fixed-effects regression model are
reported in Table 3. The model
is specified so that age, MMSE and Barthel covariates are interacted with a
dummy variable indicating whether the patient was in long-term institutional
care (Ii=1) or not (Ii=0). The results are discussed for each covariate in
turn.
|
|
Institutionalisation
As predicted, the patients incur an additional cost of approximately
£8000 per four-month period when in institutional care, assuming
everything else is held constant. This is approximately equivalent to the
annual cost of institutional care noted in
Table 1.
Age
The model indicates that the ageinstitutionalised interaction term
is significantly inversely associated with cost. When all other factors are
held constant, each additional year of age reduces the cost incurred by
£130 per four-month period, although this is not in itself statistically
significant. When cared for in an institution, each additional year of age has
the additional effect of significantly reducing four-monthly costs by a
further £147 (i.e. £277 in total). These results imply that,
having controlled for disease progression, older subjects at home or in an
institution are less likely to have health and social care resources committed
to them.
Measures of disease progression
The results indicate that changes in both the MMSE and Barthel scores have
an independent and significant effect on costs, and that changes in the
Barthel index have a larger impact. Each one-point decline in the MMSE score
is associated with a £56 increase in four-monthly costs, whereas each
one-point fall in the Barthel index is associated with a £586 increase
in costs. Even allowing for the shorter range of the Barthel scale (20 points,
compared with 30 points in the MMSE scale), it seems that changes in ADL have
a much greater impact than cognitive changes on the health and social care
resources required by dementia sufferers.
However, looking at the MMSE/Barthel and institutionalisation interaction terms, it appears that the pattern just described holds only for those outside institutional care. Once in institutional care, the results suggest that most costs are fixed and therefore further declines in cognition or ADL have little additional impact on costs (although more detailed information on patient-specific nursing and other care inputs in institutional care would be required to confirm and explain this fully). The variable wakefulness for reasons other than passing urine is the only behavioural variable to have a significant impact on the care costs. In fact, this variable significantly reduces costs by over £1000, perhaps because it correlates with other factors that reflect increased independence and therefore may be associated with a delay in the time to institutionalisation.
Time to permanent institutional care
The conditional probability that a patient with dementia is admitted to
permanent institutional care is likely to depend on his/her mental, physical
and behavioural abilities combined with the support available from carers and
community services. Table 4
shows the results for the Cox proportional hazards regression, in which time
to institutionalisation is used to determine the way in which these factors
affect the hazard of time to admission.
|
Age
The analysis shows a significant association between the age and the hazard
of institutionalisation, indicating that as the individual ages, the hazard of
being admitted to institutional care increases: this is indicative of a
reduced time to institutionalisation. Because all subjects were living at home
at entry to the study and had a mean age of 78 years, this result may have
been anticipated, however, it should be noted that this age effect is
identified after controlling for disease progression and carer commitment and
capability.
Gender
A significant association between gender and the hazard of
institutionalisation is also found, with women having a lower hazard than men
(approximately 10% lower than men), implying longer times to
institutionalisation (see Table
4).
The MMSE, Barthel and other measures of behaviour
As noted earlier, an advantage of this study compared with many others in
the area is the presence of more than one measure of disease progression,
allowing the opportunity to assess the relative importance of cognitive
decline, behavioural change and ADL. The results indicate that both the MMSE
score and the Barthel index are negatively associated with the hazard of
institutionalisation: as each declines, along with the patient's
deterioration, the hazard of being admitted increases and consequently the
duration to institutionalisation falls. The inclusion of extra behavioural
variables that measure wakefulness and aggressive behaviour that are not
captured by the MMSE or Barthel index has no impact on the significant
independent association between MMSE, Barthel and the hazard of being admitted
to long-term care. This finding that cognition and ADL have an
independent and highly significant (P<0.004) effect on the likelihood of
being institutionalised may have important implications for future
study designs and analyses.
Domestic circumstances
Three measures were included relating to domestic circumstances: who the
subject lived with, the attitude of the carer to caring at study entry and the
physical ability of the carer to cope with caring. The results indicate that,
when exploring the impact of who the patient lived with, living with others
(including at least one member of the patient's family) significantly reduces
the hazard of institutionalisation relative to living alone, and the strongest
effects were found where the number of potential carers was highest. Living
with others from outside the patient's family also seemed to reduce the hazard
of institutionalisation relative to living alone, but this effect was not
statistically significant. (Even though subjects were categorised as living
alone, they were still closely supervised by family/friends.) The results also
indicate that the presence of a carer who has an active preference for caring
for the subject at home (as assessed at baseline) significantly reduces the
hazard of institutionalisation. Finally, there is no evidence of an
independent association between the assessed physical ability of the carer to
cope and the hazard of institutionalisation.
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Modelling disease progression on the basis of changes in cognition
and ADL
One of the key findings from this study is that it may be inappropriate to
model disease progression in dementia solely on the basis of measures of
cognitive change. It has been suggested elsewhere
(Davies et al, 2000;
McDonnell et al, 2001) that
changes in scores for ADL and information on behavioural disturbances may be
potential indicators of progression to institutional care and costs of care.
This study has shown that the MMSE and the Barthel index are independent
significant predictors of time to institutionalisation and cost of care, but
changes in the levels of ADL seem to be much more important than changes in
cognition in predicting costs outside institutional care. It is also
interesting to note that despite the inclusion of measures of behavioural
disturbances not captured by the MMSE or Barthel index, such as wakefulness
and aggression, the MMSE and Barthel index remain independent significant
predictors of time to institutionalisation and care costs. This finding may
have wide-ranging implications for future studies in this area: for example,
pivotal trials of therapies for dementia have placed a strong emphasis on
changes in cognition, and almost all the modelling work conducted to date on
the cost-effectiveness of dementia interventions uses the impact of therapy on
cognition as the linking mechanism to costs of care. The possibility that
cognitive changes lead to changes in ADL would require further investigation,
but such research goes beyond the bounds of the current study.
Institutionalisation and respite care
The study confirms findings from previous research that
institutionalisation represents a significant proportion of the total cost
burden for dementia patients. Institutionalisation accounts for 69% of the
total care costs and, when all other factors are held constant, it adds an
additional cost of approximately £8000 per four-month period. Less
expected is the finding that respite care represents the next most important
burden of resource use, accounting for 15% of the total care costs for
dementia patients. This suggests that more attention should be paid to the
collection of information on respite care in prospective studies and that
onset of need for respite care should be included in modelling studies.
In contrast with the majority of previous studies which have assumed costs to be constant once a person with dementia is admitted to institutional care a feature of this study is that the costs of care in institutions do not consist solely of the flat rate cost per week of the institution, but also include such items as GP consultations, out-patient visits and short-term hospital stays. Some evidence exists on health service use among elderly people in institutional care, but not specifically those with dementia (Kavanagh & Knapp, 1998). A valuable extension to this study would be to explore in more detail the variation in the actual nursing care and other resources used by individuals within an institutional setting: in the absence of such data, there is no clear evidence that disease progression while in institutional care increases costs. However, the finding in this study that age is inversely associated with the cost of care both at home and in institutional care is intriguing, because it suggests the possible existence of age-related rationing: controlling for everything else, a person with dementia appears less likely to get access to health and social care as his/her age increases.
Lifetime costs of dementia
Finally, the empirical estimates of the effects of disease progression on
care costs that this study has established should be valuable in assessing
more accurately the true lifetime costs of dementia and their association with
disease progression and, in future work, modelling the cost-effectiveness of
therapeutic interventions.
![]() |
Clinical Implications and Limitations |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
LIMITATIONS
![]() |
ACKNOWLEDGMENTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Bosanquet, N., May, J. & Johnson, N. (1998) Alzheimer's Disease in the United Kingdom: Burden of Disease and Future Care. London: Imperial College of Science, Technology and Medicine, University of London.
Cox, D. R. & Oakes, D. (1984) Analysis of Survival Data. London: Chapman and Hall.
Davies, B., Fernández, J. & Nomer, B. (2000) Equity and Efficiency Policy in Community Care: Needs, Service Productivities, Efficiencies and their Implications. Aldershot: Ashgate.
Ernst, R. L., Hay, J. W., Fenn, C., et al (1997) Cognitive function and the costs of Alzheimer disease. An exploratory study. Archives of Neurology, 54, 687 -693.[Abstract]
Folstein, M. F., Folstein, S. E. & McHugh, P. R. (1975) Mini-mental state. A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 12, 189 -198.[CrossRef][Medline]
Gray, A. & Fenn, P. (1993) Alzheimer's disease: the burden of illness in England. Health Trends, 25, 31 -37.[Medline]
Greene, W. (1999) Econometric Analysis (4th edn). New Jersey: Prentice Hall.
Hope, T. & Fairburn, C. G. (1992) The Present Behavioural Examination (PBE): the development of an interview to measure current behavioural abnormalities. Psychological Medicine, 22, 223 -230.[Medline]
Hope, T. Keene, J., Fairburn, C., et al (1997a) Behaviour changes in dementia. 2: Are there behavioural syndromes? International Journal of Geriatric Psychiatry, 12, 1074 -1078.[CrossRef][Medline]
Hope, T. Keene, J., Fairburn, C., et al (1997b) Behaviour changes in dementia. I: Point of entry data of a prospective study. International Journal of Geriatric Psychiatry, 12, 1062 -1073.[CrossRef][Medline]
Hope, T., Keene, J., Fairburn, C., et al (1998) Predictors of institutionalization for people with dementia living at home with a carer. International Journal of Geriatric Psychiatry, 13, 682 -690.[CrossRef][Medline]
Hux, M. J., BJ, O. B., Iskedjian, M., et al
(1998) Relation between severity of Alzheimer's disease and
costs of caring. Canadian Medical Association Journal,
159,
457
-465.
Jonsson, L., Lindgren, P., Wimo, A., et al (1999) Costs of mini mental state examination-related cognitive impairment. PharmacoEconomics, 16, 409 -416.[Medline]
Kavanagh, S. & Knapp, M. (1998) The impact
on general practitioners of the changing balance of care for elderly people
living in institutions. BMJ,
317,
322
-327.
Kavanagh, S. & Knapp, M. (1999) Cognitive disability and direct care costs for elderly people. British Journal of Psychiatry, 174, 539 -546.[Abstract]
Kavanagh, S. & Knapp, M. (2002) Costs and
cognitive disability: modelling the underlying associations.
British Journal of Psychiatry,
180,
120
-125.
McDonnell, J., Redekop, W. K., Van der Roer, N., et al (2001) The cost of treatment of Alzheimer's disease in The Netherlands. PharmacoEconomics, 19, 379 -390.[Medline]
McNamee, P., Gregson, B. A., Buck, D., et al (1999) Costs of formal care for frail older people in England: the resource implications study of the MRC cognitive function and ageing study (RIS MRC CFAS). Social Science and Medicine, 48, 331 -341.[CrossRef][Medline]
Netten, A. (1990) An Approach to Costing Informal Care. PSSRU Discussion Paper No 637. Canterbury: University of Kent.
Netten, A., Dennet, J. & Knight, J. (1998) Unit Costs of Health and Social Care. Canterbury: Personal Social Services Research Unit, University of Kent.
Netten, A., Dennet, J. & Knight, J. (1999) Unit Costs of Health and Social Care. Canterbury: Personal Social Services Research Unit, University of Kent.
Porsdal, V. & Boysen, G. (1999) Costs of health care and social services during the first year after ischemic stroke. International Journal of Technological Assessment of Health Care, 15, 573 -584.
Souetre, E. J., Qing, W., Vigoureux, I., et al (1995) Economic analysis of Alzheimer's disease in outpatients: impact of symptom severity. International Psychogeriatrics, 7, 115 -122.[Medline]
Souetre, E. J., Thwaites, R. M. & Yeardley, H. L. (1999) Economic impact of Alzheimer's disease in the United Kingdom. Cost of care and disease severity for non-institutionalised patients with Alzheimer's disease. British Journal of Psychiatry, 174, 51 -55.[Abstract]
Wade, D. T. & Collin, C. (1988) The Barthel ADL Index: a standard measure of physical disability? International Disability Studies, 10, 64 -67.[Medline]
Received for publication September 6, 2001. Revision received March 11, 2002. Accepted for publication March 21, 2002.