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| Journal of the New Zealand Medical Association,
29-June-2012, Vol 125 No 1357
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The most deprived Auckland
City Hospital patients (2005–2009) are 10 years younger and have a 50%
increased mortality following discharge from a cardiac or vascular admission
when compared to the least deprived patients
Chris Ellis, Andie Pryce, Garth MacLeod, Greg Gamble
Patients admitted to a public hospital should have the same
access to investigations and treatment regardless of their socioeconomic status
and thus anticipate similar outcomes. Equity is a stated aim of the New Zealand
Medical Association.1 However, for nearly all
causes of death in New Zealand large socioeconomic mortality gradients have been
reported.2 Inequities have been observed in
clinical management of acute coronary syndrome patients in hospitals with and
without invasive facilities.3,4
The long-term intervention with pravastatin (LIPID) trial
showed that in both Australia and New Zealand increased mortality was associated
with decreased income, a marker for socioeconomic status in
patients.5 These findings may have been
exacerbated by poor health delivery structures with sparse clinical (doctor and
nursing) input into management.6
Heart failure hospitalisations and death also increase with
increasing deprivation in New Zealand.7 In New
Zealand, Canada, England and the United States of America, analyses of national
statistics showed worsening health care indicators in the most deprived compared
with the least deprived quintile of socioeconomic
status.8
We examined how medium to long-term patient outcomes may be
affected by social deprivation following hospital discharge. It has been
previously stated that New Zealand needs to consider the totality of information
to manage its health system effectively9.
However to date no descriptive data have been published on patient outcome
following a cardiac or vascular discharge from a New Zealand hospital. Further,
a descriptive audit of post discharge mortality in relation to admission
deprivation level is lacking.
We aimed to describe the 30 day and 1 year mortality of any
cardiac or vascular discharge in adult patients (age ≥15 years). We also
planned to compare the mortality rates of these patients, by deprivation index
(after adjustment for age and gender).
MethodsStudy design and subjects—The
study population comprised all patients resident within the ADHB region aged 15
years or more discharged from an Auckland District Health Board (ADHB) hospital
between 1 July 2005 and 31 December 2009 with a cardiac or vascular diagnosis
related group (DRG)10 (Appendix 1). Each of these patients was matched for
subsequent events to 1 June 2010.
The study was judged by expedited review by the North
Health Ethics committee to be an audit and therefore approved without further
review. The definition of an admission is that the patient had been in hospital
at least three hours after being seen by a doctor or the patient had a
procedure. If two or more admissions were present within the audit period the
first admission was counted as the index admission.
Each patient hospital discharge is coded and
categorised into a DRG which classifies admissions according to the resources
consumed.10 DRGs are assigned on the basis of
the International Classification of Diseases (ICD)
diagnoses,11 procedures, age, gender, discharge
status, and the presence of complications and/or comorbidities.
Within the discipline of cardiology there are 67 DRGs
which, for the purposes of aggregating numbers, can be amalgamated further into:
acute coronary syndrome (ACS)/circulatory management, congestive heart failure
(CHF), electrophysiology (EP), general cardiology, cardiac surgery and
peripheral vascular disease (PVD) management.
During the audit period each unique patient contributed
an index (i.e. first) admission and the date of a second (and number of
subsequent) readmission(s) to any ADHB hospital. Patients with an index
admission were matched against the national death register and the date of death
and the cause of death integrated.
The domicile code for each patient was obtained from
the hospital information system and was linked to the New Zealand Deprivation
2006 (NZDep2006) Index.12 Socioeconomic status
was then reported as decile of deprivation from 1 (least deprived) to 10 (most
deprived). The NZDep2006 is a small area index of deprivation that provides a
score for each mesh block in New Zealand based on nine variables (material and
social domains of deprivation) from the 2006
Census.12 The NZ Deprivation Index is more
strongly correlated with cardiovascular disease and diabetes than the NZSEI or
income.13,14
In official statistics “prioritised
ethnicity” is assigned as Māori15 if
one of the three possible self-identified ethnicity responses was Māori.
This represents the total Māori ethnic group. For those not allocated as
Māori, the person is assigned as Pacific Island ethnic group if one of the
self-identified ethnic groups was Pacific Island ethnic group, then Asian if an
Asian ethnic group is recorded. Residual patients are then classified as
European or ‘other’ ethnicities. Since the Indian ethnic group
comprised a significant proportion of the ‘Asian’ ethnic groups
these data have been presented separately from the ‘Asian’ category
in this paper.
Statistics—Data
were summarised as rates and 95% confidence intervals. Logistic regression was
used to make comparisons after adjustment for age, gender and ethnicity and the
results are presented as odds ratios and 95% confidence intervals. Cox
proportional hazards models (with adjustment for age, gender and ethnicity) were
used to compare survival time amongst the groups of interest.
Results were presented as hazard ratios (with 95%
confidence intervals) and the proportionality assumption was tested. Tests of
linear trend were performed using orthogonal contrasts for normally distributed
tests and the Cochran-Armitage test for ordinal data. All analyses and data
manipulations were performed using SAS statistical software (SAS Institute Inc,
v 9.2). Patient years were calculated for each patient as the time from index
admission to the end of follow-up or death. Events per patient year were
calculated using OpenEpi (www.openepi.com
All tests were two-tailed and P<0.05 was considered statistically
significant.
ResultsThese data show that when compared to the least deprived
patients, the most deprived patients are 10 years younger and have a 50% age and
gender-adjusted increased mortality following discharge from a cardiac or
vascular admission to Auckland City Hospital in 2005–2009.
Unadjusted data—From 1 July 2005 to
31December 2009 there were 19,545 cardiac patient discharges from patients
resident in the Auckland District Health Board (ADHB) region. Most (50%) were
related to acute coronary syndrome or circulatory management, 30% were
classified as ‘general cardiology’ with small proportions (<10%
each) categorised as CHF, EP, cardiac surgery or PVD management (Table 1).
Overall, the numbers of cardiac discharges were similarly
spread across the NZDep Index ranging from 18 to 23% (P=0.87, Table 1). However,
those patients discharged following cardiac surgery showed increasing
proportions of discharges from more deprived patients (P=0.037). In contrast the
number of patients discharged following EP management showed increasing
proportions from less deprived patients (P=0.04, Table 1).
All-cause mortality following a hospital discharge over a
median 2.4 years follow-up was 6.2 deaths per 100 patient years follow-up (Table
1). Unadjusted mortality was higher (6.9 deaths/100 patient years) in
those attributed to the least deprived category in comparison with the most
deprived category (5.7 deaths/100 patient years) (P<0.05, Table 1) . However,
the most deprived patients tended to be 10 years younger than the least deprived
(57 years vs 66 years P<0.0001), and were more likely to be male (55% v 50%,
P<0.0043, Table 2).
The average age at discharge was 61 years (SD 19) (Table 2).
All-cause unadjusted mortality was highest for those following a CHF
discharge (28 deaths/100 patient years) and lowest following ACS and circulatory
management discharge (4.1 deaths/100 patient years) (Table 1).
The proportion of European ethnicity decreased and the
proportions of patients with prioritised Māori or Pacific Island ethnicity
increased with increasing deprivation (P<0.0001) (Table 2). The most deprived
patients had a significantly longer length of stay, (on average one day more
P<0.0001) and they had more diagnoses reported at discharge (P<0.0001)
which is a simple surrogate for patients who are more unwell with more
comorbidities (Table 2).
Across categories of unadjusted deprivation there
were no differences in the in-hospital death rates (overall 1.8%, P=0.23), or
death at 30 days (overall 3% P=0.075) or at 1 year (overall 8.1%, P=0.40) after
a cardiac discharge (Table 3). However, by a median follow-up of 2.4 years,
unadjusted least deprived patients had a greater mortality (but were
approximately 10 years older). Increasing deprivation was associated with
increased readmission rates (Table 3).
Table 3. Readmissions to an Auckland District
Health Board hospital until 1 June 2010
Note: All-cause death to 1 March 2009
(unadjusted data). Outcome following any cardiac discharge 1 July 2005 to
31 December 2009 in Auckland District Health Board Residents aged 15 years and
over.
[(-) indicates trend for decreasing number with
increasing deprivation (+) indicates trend for increasing number with increasing
deprivation.]
Depr: Deprived; FU: Follow-up; Readmiss: Readmission
[to hospital].
The characteristics of patients discharged following ACS and
circulatory management show a similar pattern to the entire cardiac cohort:
deprived patients are younger, more likely to be male and to have a larger
proportion of patients of Māori or Pacific Island origin (Table 4). They
also had increased number of discharge diagnoses (a crude measure of
co-morbidities) and longer length of stay (Table 4).
Table 4 “ACS and Circulatory
Management” diagnosis-related group discharges 1 July 2005 to 31 December
2009 in ADHB residents aged 15 years and over (unadjusted
data).
Note: [see Appendix for acute coronary
syndrome/invasive management 20 Diagnosis Related Group codes).
(-)indicates trend for decreasing number with increasing deprivation (+)indicates trend for increasing number with increasing deprivation.] LOS: Length of stay; SD: Standard deviation; IQR:
Interquartile range.
There are no differences in deaths following ACS and
circulatory management admissions across deprivation levels using the unadjusted
data however the number of readmissions increases with worsening deprivation
(Table 5).
Table 5. Readmissions to an Auckland District
Health Board hospital until 1 June 2010. (All-cause death to 1 March 2009
(unadjusted data) for acute coronary syndrome/circulatory diagnoses.)
Note:
Outcome following an acute coronary syndrome/circulatory management cardiac
discharge 1 July 2005 to 31 December 2009 in Auckland District Health Board
Residents aged 15 years and over. [(-)indicates trend for decreasing number with
increasing deprivation (+)indicates trend for increasing number with increasing
deprivation.]
Adjusted data—From the
unadjusted data it is seen that the most deprived patients are 10 years
(57 v 66 years, P<0.0001) younger and males are more frequently (54% v 50%
P<0.0001) admitted in the most deprived group. Therefore to assess overall
mortality over time the data needs to be age and gender adjusted to fully assess
the impact of deprivation.15
Figure 1 shows the age and gender adjusted risk
estimates of death, and the composite death/readmission for each NZDep Index
level, compared to the least deprived group. Throughout the follow up, death at
1 year and at 2.4 years of follow-up, and the composite endpoint of
death/readmission, were significantly increased (all P<0.0001) in the most
deprived NZ Dep Index: category 9-10 compared with the least deprived NZ Dep
Index: category 1-2. For these endpoints the trend was a linear increase across
the groups.
Figure 1 also shows that short term 30-day mortality has a
similar pattern, with mortality increasing with increasing levels of
deprivation, however the confidence intervals were wide and the trend failed to
reach conventional statistical significance. The same pattern was apparent for
an analysis restricted to acute coronary syndrome/circulatory management patient
admissions (Figure 2).
Figure 1. Mortality after any cardiac admission
(all 67 cardiac Diagnosis Related Groups see Appendix 1) to an Auckland District
Health Board hospital by deprivation index. (Age and gender adjusted
data.)
 Figure 2. Mortality after an acute coronary
syndrome/circulatory management admission (20 Diagnosis Related Group categories
see Appendix 1) to Auckland City Hospital. (Age and gender adjusted
data.)
 Cox proportional hazards modelling was performed for time to
all-cause death at a median follow up of 2.4 years after a cardiac admission and
adjusted for age and gender (Figure 3A) and with additional adjustment for
ethnicity (Figure 3B).
Figure 3A. Age/Gender adjusted hazard
of all cause mortality after a cardiac admission to Auckland City Hospital
 Figure 3B. Age/Gender/Ethnicity adjusted
hazard of all cause mortality after a cardiac admission to Auckland City
Hospital
 Adjusting for age, gender, ethnicity and length of stay
attenuated the result slightly however increasing deprivation remained
significantly associated with increased mortality (NZ DepI 1-2 HR=1, NZ DepI 2-3
HR=1.08 (1.0,1.2) P=0.18, NZDep I 4-6 HR=1.14 (1.0, 1.3) P=0.02, NZDepI 6-8
HR=1.15 (1.0,1.3) P=0.02, NZDep I 8-10 HR=1.20 (1.01, 1.08) P<0.0001).
Similar modelling was performed for an ACS and circulatory
management admission and adjusting for age, gender (Figure 4A) and additionally
for ethnicity (Figure 4B). Overall, and for those with ACS and circulatory
management discharges the same pattern was seen, a statistically significant
increase in risk of early death with increasing deprivation. Adjustment for
ethnicity, in addition to age and gender did not change this observation.
Unadjusted all-cause mortality was higher at a median follow
up of 2.4 years (17%) in the least deprived group (NZDep 1-2) compared with the
most deprived group (NZDep 9–10) (14%) (P=0.0018, Table 6).
Table 6. All-cause mortality at a median
follow-up of 2.4 years by ethnic group in the least deprived and most deprived
groups
There were no differences in all-cause age/gender
adjusted mortality across ethnic groups for those in the least deprived
group however in those classed most deprived, Māori and Pacific people were
at increased risk of age/gender adjusted death compared to Europeans
following cardiac discharge whilst Asians were at reduced risk (Table 6).
In comparison to least deprived (NZDep 1-2) Europeans, the
most deprived (NZDep 9–10) Europeans, Māori and Pacifica peoples had
significantly increased age and gender adjusted all-cause mortality (Figure
5).
Overall, men had a 20% age-adjusted increased risk of
all-cause death at a median follow-up of 2.4 years compared with women (HR 1.2
(95%CI 1.14–1.32, P<0.0001) and the risk of all-cause mortality
increased with increasing deprivation in both men and women (Figure 6).
When considering the age of the patient (Figure 7), the
association with deprivation was most pronounced in those aged <60 years with
increasing risk of gender adjusted death with increasing level of deprivation
(p=0.0063 for trend across first to last Dep levels).
In patients aged 60 to 75 years the association was present,
but less pronounced (p=0.0006 across Dep levels). In those aged > 75
years there was no association between risk of all-cause death and worsening
deprivation (p=0.096 across Dep levels, Figure 7). These data suggest that
deprivation is associated with a marked shortening of life in younger age
groups.
Figure 4A. Age/Gender adjusted hazard
of all cause mortality after an acute coronary syndrome or circulatory
management admission to Auckland City Hospital
 Figure 4B. Age/Gender/Ethnicity
adjusted hazard of all cause mortality after an acute coronary syndrome
or circulatory management admission to Auckland City Hospital
 Figure 5. Age/gender adjusted risk of
all cause death in those most (New Zealand Deprivation Index 9-10) and least
deprived (New Zealand Deprivation Index 1–2) by ethnic origin (data are
hazard ratio 95%CI). P is for comparison against referent group (least deprived
Europeans).
 Figure 6. All-cause mortality for men and women
by New Zealand Deprivation Index (overall age adjusted) for men
compared to women is 1.2 (95% CI1.14, 1.32) P<0.0001.
 Figure 7 All cause mortality for men and women
by New Zealand Deprivation Index (overall gender adjusted) for those
aged > 75, 60-65 and < 60 at discharge.
 DiscussionAbout 8% of all discharges from an Auckland District Heath
Board hospital are cardiac or vascular, comprising roughly equal proportions of
people across the categories of the NZ Deprivation Index. About half of all
cardiac or vascular admissions are for “acute coronary syndrome and
circulatory management”.
Overall, subsequent mortality is low (6.2 deaths /100
patient years). Patients who were most deprived were 10 years younger than those
who were least deprived and more likely to be male. Hence, although fewer deaths
are observed in those who are most deprived (5.7 deaths/100 patient years) than
in those who are least deprived (6.9 deaths /100 patient years), an age and
gender adjustment is clearly needed, and then the overall risk of
all-cause mortality over a median 2.4 years follow-up is 50% greater for those
most deprived in comparison with the least deprived group.
Previous studies have shown large socioeconomic mortality
gradients exist for nearly all causes of deaths in the New Zealand
community.2 The New Zealand census-mortality
study examined age and ethnicity standardised mortality for 25-94 years. They
compared NZ deprivation index groups 9 and 10 (most deprived) with groups 1 and
2 (least deprived).
All-cause mortality was 2.0 (1.9, 2.2) for men and 2.1 (1.9,
2.3) for women. Cardiovascular disease rate ratios were 2.4 (2.1, 2.8) for men
and 2.4 (2.0, 3.0) for women.16 The same
pattern persists in these data, in patients following a cardiac or vascular
admission to Auckland City Hospital.
More Māori and Pacific Islands people are likely to be
classified as most deprived. After adjustment for this imbalance, a consistent
linear increase in risk of early death is still seen with increasing levels of
deprivation, suggesting that deprivation results in a worse outcome independent
of ethnicity.
When a patient’s ethnicity is considered, in patients
identified as least deprived there is no difference in age and gender
adjusted all-cause mortality across ethnic groups. However in the most
deprived patients, Māori and Pacific Islands people have significantly
increased mortality compared to similarly deprived European patients. Asian
patients tend to have reduced all-cause mortality compared to Europeans.
This observation suggests an added risk for those of
Māori or Pacific Islands ethnicity in those who are most deprived. This may
reflect barriers to primary or secondary healthcare services which might prevent
or delay acute hospital admissions, and/or failures of primary screening.
Marked ethnic and socioeconomic disparities in the
prevalence of cardiovascular disease in New Zealand has been shown in a
2006-2007 cohort.17
Māori had the highest age-standardised prevalence
compared to the rest. Prevalence of cardiovascular disease increased with
increasing deprevation.17 Deprivation is also
known to be associated with increased risk of heart failure death or heart
failure admission which has been shown to be worse overall for
Māori.7
There are several possible reasons for the more deprived
having a worse outcome. First, there may be differences at presentation. At
presentation more deprived patients may have more (or more severe) comorbid
conditions, or may delay their presentation to hospital or may have experienced
less effective primary care.
Younger patients presenting to the coronary care unit at
Middlemore Hospital have a worse cardiovascular risk profile, and are more
likely to be obese, to smoke, to have low HDL and high triglyceride
levels.18 However
Malcolm19 found that in 127,426 primary health
organisation (PHO) patients that Māori actually had better access to
cardiology inpatient services than non-Māori.
Further, the New Zealand Acute Coronary Syndrome Audit of
2002 showed that in-patient management was a reflection of geographical location
and service provision, and not of ethnicity.2
Second, there may be different treatment of patients during
their inpatient admission as it is possible that treatment within hospital
differs by socioeconomic status, although this seems unlikely. Supporting data
for the absence of a treatment bias within the hospital might come from the
survival curves from these data.
Early deaths are not split by deprivation; it is late deaths
that are driving this effect. Hence the comprehensive public practice within a
hospital may be unbiased, but after hospital discharge, the ongoing medical
effects of socioeconomic deprivation are seen.
Third, there may also be differences with pre-hospital
deaths, outpatient follow-up, or patient adherence to appropriate lifestyle or
medication, or a range of other unknown differences.
The differences in access to treatment are more likely to be
greater between hospitals than within a hospital and may present as a
socioeconomic difference when the hospital supports a lower SES demographic.
Ellis et al have shown that patients are less likely to receive interventional
cardiology if they don’t present to an interventional centre.
Non-interventional centres are more likely to be rural and
poor.3
These data also suggest that deprivation is associated with
a marked shortening of life in younger age groups after a cardiac or vascular
admission. It is unclear why the effect of deprivation is not seen in the older
age groups. Possible reasons include: the younger more deprived members have
already died; older patients may live in less deprived suburbs, and since the NZ
Deprivation Index is driven by address, some older patients may be misclassified
as they may have now a standard income: the pension, the same as with people
from ‘more deprived’ people, and therefore may be less able to
access extra assistance e.g. private health care which could result in better
outcomes with earlier assessment and management of medical problems.
There are a number of potential limitations for this study
including the relatively small number of Māori or Pacific Islands people in
the lower deprivation categories, a focus on all-cause mortality, reliance on
information extracted from the official admissions record (which has no
information on the severity of casemix at presentation) and using patients
self-reported (but verified) address to model socioeconomic status, as a few
individuals may have been misclassified by providing incorrect address
information.
Whilst the external validity (generalisability) of these
conclusions is unchanged, since these represent an analysis of official
statistics for a large number of consecutive admissions at a major tertiary
hospital, the conclusion must be tempered by the understanding that the internal
validity might be reduced by confounding factors.
ConclusionSocioeconomic deprivation is associated with earlier age at
presentation and a markedly increased chance of death and hospitalisation
following discharge from a cardiac or vascular related admission to a public
hospital in New Zealand. These data are of considerable concern and highlight
the clear need to develop and implement comprehensive strategies to improve on
this health inequality within the New Zealand health care environment.
Competing interests: None known.
Author information: Chris Ellis,
Cardiologist , Green Lane CVS Service, Cardiology Department, Auckland City
Hospital, Auckland; Andie Pryce, Clinical Analyst, Auckland City Hospital,
Auckland; Garth MacLeod, House Officer, Auckland City Hospital. Auckland; Greg
Gamble, Statistician, University of Auckland
Correspondence: Dr Chris Ellis, Cardiology
Department, Green Lane CVS Service, Level 3, Auckland City Hospital, Grafton,
Auckland 1023, New Zealand. Email: chrise@adhb.govt.nz
References:
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