Depression and other psychiatric morbidity in carers of elderly people living at home

SAMPLE SELECTION

We conducted the survey in the London Borough of Islington, the sixth most deprived of the 403 local government areas in England and Wales.12 We selected enumeration districts in Islington randomly. We delivered an introductory letter to every address in each selected district explaining that a doctor interested in the health and services received by elderly people would visit. We made an appointment to interview all people aged 65 years and over. If no one was in, the interviewer called again until the subject was located. This technique has previously been reported as an accurate sampling technique to use in inner city areas.13

We defined carers as those living with an elderly person with major psychiatric illness (dementia or depression) or with physical disability as defined below. We classified the carers into subgroups by the diagnosis of the person for whom they cared. We reached diagnoses using a hierarchical, mutually exclusive system,14 with dementia at the apex, followed by depression and then physical disability (defined as limited activity in the absence of psychiatric morbidity). This generated mutually exclusive comparison groups of carers and enabled a group needing care for purely physical reasons to be identified.

Coresidents were defined as those living in the same household as an elderly person without such psychiatric morbidity or physical disability. Anyone (irrespective of his or her age) living in the same household as an elderly person was thus either a carer or a coresident.

THE INTERVIEW

All subjects were interviewed by a trained, medically qualified interviewer (MM), with the following interview schedules (diagnoses of the same condition generated by either method were regarded as equivalent).

For those aged >/=65 we used (a) the shortened version of the comprehensive assessment and referral evaluation,15 a valid and reliable semistructured questionnaire with diagnostic scales for depression and dementia, screening scales measuring sleep disorder, somatic symptoms, and subjective memory problems, and an activity limitation scale (designed to identify those needing help with daily living)16; and (b) an anxiety disorder scale17 validated against clinical diagnosis18 and generating diagnoses of generalised and phobic anxiety. Further details are given in an earlier paper.19

For those aged <65 we used the revised clinical interview schedule,20 a valid and reliable measure of psychiatric morbidity for adults in that age group. Additional questions were added to enable specific diagnoses according to ICD-10 (international classification of diseases, 10th revision) to be made.21

DATA ANALYSIS

Carers and coresidents were divided by sex before further analysis as men and women differ in vulnerability to the psychological effects of caring.11 Data were analysed with SPSS-PC+.22 Initial univariate analyses were carried out with χ² test or Fisher's exact test (confidence intervals calculated with Cornfield's or Fisher's exact test) with subsequent logistic regression analysis.

DEMOGRAPHIC

We approached 782 subjects aged 65 and over, of whom 700 (90%) were interviewed. Of the 82 people who refused, eight lived with a spouse who agreed to be interviewed. In addition, we approached 79 people aged under 65, of whom 60 (76%) agreed to be interviewed.

Of the 700 subjects aged >/=65 (range 65-100; mean 75.7) years who were interviewed, 447 were women, 338 lived alone, 307 lived with a spouse (although two of these lived not only with a spouse but also with another person), and 55 lived only with someone other than a spouse.

In all, 118 out of the 760 subjects interviewed were carers, of whom 86 were aged >/=65 and 32 <65. Their ages ranged from 39 to 90 (mean 70.3) years. Sixty four of the carers were women. Of the 277 coresidents (of whom 249 were aged >/=65 and 28 <65; age range 47-95 (mean 72.6) years), 148 were women. Analysis of variance comparing mean age, with carer or coresident status and sex as covariates, showed that coresidents were older than carers (P<0.05) but that sex was not significantly related to carer or coresident status.

Of the 91 carers who were spouses, 78 were aged >/=65 and 13 <65. Nineteen carers (18 aged <65) cared for a parent and eight cared for a more distant relative. The coresidents comprised 237 spouses (212 aged >/=65 years and 25 <65), 21 children (20 aged <65 years and one aged >/=65), and 19 more distant relatives (17 aged >/=65 years and two <65).

DISEASE AND ILLNESS IN SAMPLE AGED >/=65

Table 1 shows the proportion of subjects aged >/=65 years with specific psychiatric diagnoses, sleep disturbance, or limited activity.

CLASSIFICATION OF CARERS

Of the 118 carers, 22 (15 of whom were women) cared for people with dementia, 33 (15 women) for people with depression, and 63 (34 women) for physically disabled people.

DEPRESSION IN CARERS, CORESIDENTS, AND PEOPLE LIVING ALONE

Table 2 shows the prevalence of depression in the carers, coresidents, and people living alone. Among the carers of people with dementia, depression was found in nearly half of the women but in none of the men. Only 8% of the carers of people with limited activity were depressed. The women who cared for people with dementia were significantly more likely to be depressed than women coresidents (P<0.005). Depression was also significantly more likely in the carers of people with any psychiatric morbidity than in the coresidents (P<0.05) but not than in those living alone. The people living alone were, however, more likely to be depressed than the coresidents (P<0.01).

Although the rates of depression in the carers of people with limited activity were relatively low, they were not significantly lower than in the non-carers or the coresidents. Women caring for disabled elderly people, however, were less likely to be depressed than women living alone (χ²=4.40, P<0.05, odds ratio 0.13).

Among the carers of people with dementia the women were significantly more likely to be depressed than the men (P<0.05). No other significant associations of sex with psychological morbidity were found.

PSYCHIATRIC DIAGNOSES AND PSYCHOLOGICAL SYMPTOMS IN CARERS, CORESIDENTS, AND THOSE LIVING ALONE

Table 3 shows the overall rates of functional psychiatric diagnosis (depression, generalised anxiety, and phobic disorder) and psychological symptoms (sleep disturbance, somatic symptoms, and subjective memory disorder). Univariate analysis showed differences between the groups in psychiatric diagnosis (χ²=12.53, P<0.05).

With a backward stepwise logistic regression analysis—considering the effect of sex and status as coresident, carer (divided into carers of someone with a psychiatric illness and carers of someone with physical illness), or living alone—only being a woman (P<0.001) and being a carer of someone with a psychiatric diagnosis (P<0.09) remained predictors of psychiatric illness. The same analysis with symptoms as the outcome retained being a woman (P<0.01) and not being a coresident (P<0.05) as predictors.

METHODOLOGY

Our study achieved a high response rate in a community sample of all individuals aged >/=65 living in randomised districts throughout an inner London borough; the sample is therefore likely to be representative of an urban elderly population. This is borne out by the similarity between the prevalences for dementia and depression in our sample and those reported in similar studies.13 24 Our population was, however, older and of a lower social class than the elderly population in the United Kingdom as a whole.25

Despite the relatively large cohort of carers, the study had only limited power to identify associations with psychiatric morbidity in carers because of the small numbers in each category of carer. Our study was designed on the assumption of higher overall rates of psychiatric morbidity in all carers, as had been reported in previous studies.

CONCLUSION

This study suggests that, in a representative community sample, caring for people with psychiatric (rather than physical) illness predisposes to depression. This increased rate in such carers is apparent in comparisons with coresidents but not with people living alone. Further studies are under way to identify whether intervention can help to prevent depression in carers.

We thank the residents of Islington, north London, for their help and Bob Blizard for statistical advice.