Causal inferences can be drawn from routinely collected population statistics that include data on provision of unpaid care and poor health.
Data from the UK Census 2001 provides a unique opportunity to examine the nature and strength of the relationship between provision (and
independent contribution) of informal care and reported poor health whilst simultaneously controlling for a number of important covariates including age, sex, marital status and ethnic group in a data set containing
approximately 50 million people.
2.2 Background
Data from the UK Census 2001 estimates that one person in eight (six million people) in the United Kingdom ‘looks after or gives help and support to family members, friends, neighbours or others because of long-term physical or mental ill health or disability, or problems related to old age’ 46. Furthermore, 6.8 million (16% population) people aged 16 and above in the United Kingdom report that they have ‘extra responsibilities because they look after someone who has long-term physical or mental health or disability, or problems related to old age’47.
As noted in Chapter 1, providing care to another person has been
implicated as a risk factor for poor health48. However, population based studies29;49;50 and systematic reviews51 assessing the impact of exposure to informal care giving on health status either focus on a subset of the care giving population (for example women49, older people29, spouses living
with care recipient29 or those who require assistance with basic or
extended activities of daily living29 and therefore are not generalisable to the informal care giving workforce. Also, many do not take into account factors known to influence health status such as age, gender and
socioeconomic status or provide insufficient information to determine whether the carer and comparison groups differ in key characteristics (for example age, gender) which may act as confounders51.
Aim
The aim of this study was to examine the relationship between
self-reported health status and informal care giving to another person because of long-term physical or mental ill health or disability, or problems related to old age.
2.3 Methods
The objectives were to use data from the UK 2001 Census to determine whether the prevalence of reported poor health, a) was higher in those exposed to providing informal care than those who are not exposed to providing care, b) increases as exposure to care giving increases and c) could be explained by the possible confounding effects of age, gender, ethnic group, marital status, economic activity or educational attainment.
Data from the 2001 Census from respondents aged 16 and over were used.
This Census was the first to include questions on the provision of unpaid care (Box 2-1, page 2-47) and general health (Box 2-2, page 2-47). For the purpose of this manuscript, participants reporting 'not good' health are referred to as having 'poor health'. The methodology of the 2001 Population Census is described in detail elsewhere52. In summary, the Population Census is a survey that collects data from all members of the population living in England, Wales, Scotland and Northern Ireland on Census day and is performed at 10-year intervals. The Census uses self-completion forms.
The survey content includes over 40 questions covering the characteristics of the population such as age, marital status, economic activity, housing and health. A question of care giving was included in the survey from which it is possible to determine whether or not the respondent provided care to another person because of long-term physical or mental ill health or
disability, or problems related to old age, and including the number of hours care that they provided on a weekly basis. A question was also included on self-reported health status.
There is no single United Kingdom (UK) Census. The Census for England and Wales is conducted by the Office for National Statistics; the Scottish Census is conducted by the General Register Office for Scotland and the Northern Ireland Census by the Northern Ireland Statistics and Research Agency. The 2001 UK Census response rate for England and Wales is estimated to be 94%53, 96.1% in Scotland54 and 95.3% in Northern Ireland55.
Data on 46,930,509 (Figure 2-1) respondents aged over 16 were available from the Office for National Statistics (ONS)56. In order to remove a
potential source of confounding we excluded people who were classified in the economic activity category as 'permanently sick and disabled' (n = 2,464,676, 5.25%) on the basis that many of the subgroup will have had long-standing illness unrelated to care giving status. This left a total of 44,465,833 (94.75%) respondents for inclusion in this analysis.
The outcome of interest was self-reported health status. Analyses adjusted for age, sex, marital status, ethnicity, economic activity and education based on prior knowledge of factors likely to influence health status3;57;58. In addition, the number of variables available for inclusion was limited by the ONS to avoid issues related to confidentiality and
disclosure59.
Demographic covariates were categorized: age into 10-year group
categories; ethnicity (as white, mixed, Asian or Asian British, black or black British and Chinese or other as specified by the ONS56 to ensure ethnic
group consistency across the UK (Figure 2-2)); and marital status as in partnership (married, remarried), not in partnership (single, separated, divorced) or widowed.
Economic activity is categorized by the ONS as economically active (full-time, part-(full-time, self-employed, unemployed, full-time students working in the week before Census, or looking for work and available to start within two weeks), economically inactive (retired, full-time student, looking after home/family, aged 75 and over). Education qualifications were categorized as no qualifications or level 1, 2 and 3 by the ONS to ensure consistency across the UK (Figure 2-3), in addition to the categories ‘other’ and ‘aged 75 and over’.
Descriptive statistics were used to examine the characteristics of the sample and prevalence of outcomes and covariates. Differences in proportions were compared using chi-square test. Univariate analyses (unadjusted odds ratios) were used to examine the association between reported health and care giving exposure and with each covariate: age, sex, marital status, ethnic group, economic activity and educational attainment.
As the proportional odds assumption was not fulfilled when the three self-reported health categories were used ('good', 'fairly good', 'not good'), the reported health status responses were dichotomized in to 'good/fairly good' and poor ('not good'). The association between poor health and four levels of care giving exposure: no care, 1-19 hours care per week, 20-49 hours per week and 50+ hours per week was examined; no care was chosen as the reference category. Odds ratios for ‘not good’ health and their
accompanying 95% confidence intervals were computed for each care giving exposure level using binary logistic regression. Additional analyses
adjusted for age, sex, marital status, ethnicity, economic activity and educational attainment. Identical categorisation of economic activity and educational attainment for individuals aged 75 and over made simultaneous estimation of their individual regression coefficients inappropriate due to
multicollinearity. Therefore two analyses were performed 1) all ages not adjusting for economic activity and educational qualifications (Model 1), and 2) age groups 16-74 adjusting for all covariates (Model 2). Statistical analyses were performed using Minitab 15 and SAS v9.1.
2.4 Results
The baseline characteristics of all participants are shown in Table 2-1.
40,740,785 (91.6%) of the population reported their general health to be 'good/ fairly good' and 3,725,048 (8.4%) reported their health to be poor.
Of those reporting their general health to be ‘good/ fairly good', 12.2%
report providing care compared to 13.2% of those who report their health to be poor (2 test 3534.43, p < 0.001). Therefore the odds of reporting providing informal care in individuals reporting poor health are 10% (95% CI 9.6% to 10.3%; p < 0.001) higher than those who report good/fairly good health.
5,451,902 (12.3%) of the participants reported providing care to a family member, friend, neighbour or others because of long-term physical or mental ill health or disability, or problems related to old age. 8.3% of non carers report poor health. For all respondents, the prevalence of 'not good health' was significantly greater in those who reported providing care (n = 492,747, 9.0%) compared to those who did not provide care (odds ratio 1.100, 95% CI 1.096- 1.103). Table 2-2 shows the relationship between self-reported health and care giving exposure and all covariates. This table shows that the odds of poor health is increased 1) as level of exposure to care giving increases; 2) with age; 3) for females; 4) for the white ethnic group; 5) for groups classified as economically inactive retired, over 75s and other; and 6) as level of educational attainment decreases.
The full binary logistic regression models are presented in Table 2-3. Model 1, which adds demographic characteristics, reveals a diminished
association between care giving and poor health although the association
remains and the strength of association increases as the reported amount of care provided per week increases.
The second model introduces economic activity and educational
attainment. The inclusion of these factors does not alter the dose-response relationship between care giving and poor health as seen in Model 1,
although it does reduce the strength of the association. We found no important interaction between care giving exposure and each of age, sex, marital status, ethnic group, economic activity and educational
attainment.
The model R-Squared values, which indicate the proportion of variance explained, are 15.6% (Model 1) and 13.3% (Model 2).
A sensitivity analysis, including participants classified in the economic activity category as 'permanently sick and disabled' showed very similar results.
2.5 Discussion
The main finding of this study is that people who report providing informal care to 'family members, friends, neighbours or others because of long-tem physical or mental ill health or disability, or problems related to old age', have increased odds of reporting poor health compared to those who do not provide informal care. This could not be explained by potential
confounders including age, sex, marital status, ethnic group economic and education characteristics. We also found a dose response relationship, with those providing highest number of hours of care reporting the highest rates poor health and those providing the least having the lowest. The
magnitude of this association is consistent with the results from other studies that have linked informal care giving with adverse health outcomes29;49;50.
These findings have important societal implications. The health risk associated with providing informal care is relatively modest. However, a large number of people are exposed to this risk; one in 12 people in the UK provides informal care.
This is the largest study addressing the relationship between self-reported care giving exposure and self-assessed general health, using data from all adults living in the UK in 2001 who responded to the population census. In addition, unlike previous studies we have not selected carers of a
particular age, sex or care recipient group (for example those suffering from dementia or stroke survivors). Also we have not studied specific health outcomes (for example depression or coronary heart disease) but have focused on a large population using a simple, single item self-rated health status report. Using a one item self-rated health status report is an established and valid method of assessing health status60.
There are a number of possible mechanisms for how informal care giving may cause poor health. There are many and varied ‘occupational hazards’
that care givers may be exposed to. These include physical stress, for example mobilising dependent care recipients. Psychosocial stressors include care giving demands29;49;50 and conditions that are at variance with the care-givers needs, existing commitments, expectations or values or exceed their capacity, knowledge or skills; uncertainty; high care giving demands, low control and effort-reward imbalance. Problems with physical conditions can include poor access e.g. stairs, lack of environmental aids and technologies. These same conditions presenting in an employment or work environment would be recognized as physical and psychosocial hazards and therefore risk factors for physical and mental health
problems58;61. Although it is yet to be established whether such a model is plausible in explaining the relationship between exposure to informal care provision and stress, elements have been tested in carers of specific groups62;63. In addition, there is an association between stress in informal carers and immune dysregulation64, elevated blood pressure65, impaired wound healing43 and increased risk of mortality29; there is also increased
risk of coronary heart disease49 and poorer cognitive function67 among women who provide care to their disabled or ill spouses.
The care giving context including the relationship between the carer and the care recipient may also be important49;50. For example women who provide care to their disabled or ill spouses are more likely to become ill than those who care for other dependent family members49.
One limitation of this study is the cross sectional nature. Temporal associations cannot be inferred68. It is also difficult to establish whether carers have been exposed to ‘care giving’ for long enough to develop a change in health status and for the latency period to have elapsed, which is likely to lead to an underestimation of the odds of 'not good' health. In addition, we have compared currently exposed individuals with currently unexposed individuals, this does not account for their recent past history of care giving exposure which may lead to underestimation of the effect of care giving exposure as a risk factor for poor health, or regression dilution bias69.
Self-assessed general health status may also affect who takes on the care giving role. For example, in the 65 and over age group it is possible that people who report good or fairly good general health are more likely to take on the care giving role than those reporting not good health, introducing the possibility of membership bias.
The ability to adjust for confounders was limited to those variables
available as part of the UK Census 2001 and does not collect for example, information on health behaviours which may influence reported health status60. This is reflected by the relatively low R2 values of the models fitted. In addition, the number of variables available to us was also restricted by measures put in place that uphold the 2001 Census confidentiality commitments59. Ideally, we would have included self-reported long-term illness, occupation70, national statistics socioeconomic classification (NSEC) and geographical location71.
The quantification of the time spent in a typical week providing unpaid care including the validity and reliability of the self-reported time
estimates must also be taken into consideration along with the potential for reporting inaccuracies among proxy respondents. In addition, the categorization of hours of care giving into 1-19, 20-49 and 50 plus hours care per week prevented a more in-depth analysis of the relationship between care giving and health outcome over the full spectrum of number of hours of care giving. Therefore, there is the possibility of residual confounding as a consequence of measurement imprecision for included covariates, and unmeasured covariates.
However, the cross sectional design is valuable for measuring the
population burden of self-reported poor health using prevalence rates. The UK 2001 Census is unique in that it effectively gathers data on people representing almost all stages of health, disease and illness and exposures of interest. In addition, the general health outcome and carer exposure status are clear, specific and measurable. The data have been collected in the same way for the group exposed to care giving and the group not
exposed which helps prevent errors in measuring care giving exposure and self-reported health status. Additionally, those who are responsible for processing the results of the UK 2001 Census are blind to the exposure status reducing any risk of detection bias. Also, previous studies have found that a simple, one item self-reported health question similar to that used in this UK 2001 Census was associated with mortality when all other factors known to influence health and prior information about health status were controlled for60.
2.6 Conclusions
The results demonstrate that in a cross sectional study of the UK
population the prevalence of poor health is greater in those who provide informal care compared to those who do not provide informal care and that this increases with the level of exposure to informal care. In addition, use
of the data from the UK Census 2001 illustrates how a large and valid secondary data source can be accessed within a short period of time to address a research question such as assessing the relationship between exposure to care and reported poor health and to generate further research questions.