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Julia Hippisley-Cox a Division of General Practice, Nottingham
University, Nottingham NG7 2RD, b Collingham Medical
Centre, High Street, Collingham NG23 7LB, c School of Nursing, Medical School,
Queen's Medical Centre, Nottingham NG7 2UH
Correspondence to: J
Hippisley-Cox julia.hippisley-cox{at}nottingham.ac.uk
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Abstract |
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Objective:
To study differences in treatment for men and women with ischaemic heart disease by using standards defined in
England's national service framework for coronary artery
disease.
Design:
Cross sectional survey using routinely
collected data.
Setting:
18 practices in 18 primary care groups in Trent Region.
Subjects:
5891 men and women aged over 35 years with a
diagnosis of ischaemic heart disease or prescription for nitrates recorded on computer.
Main outcome measure:
Difference in the proportion of
men and women with ischaemic heart disease and taking lipid lowering treatment.
Results:
Women were less likely than men to have a recording of body mass index (79% (2197/2783) v 82%
(2552/3102), P=0.002), smoking (86% (2386) v 89% (2779),
P<0.0001), and blood pressure (95% (2643) v 96% (2986),
P=0.04). Women were also less likely to have a recording of fasting
cholesterol concentration (35% (968) v 50% (1550),
P<0.0001) but were more likely to be obese (25% (558/2197)
v 20% (514/2552), P<0.0001) and have their most recently
recorded blood pressure value over the recommended 140/85 mm Hg (60%
(1598/2643) v 52% (1553/2986), P<0.0001). Although a
higher proportion of women had a raised serum cholesterol concentration (77% (749/968) v 67% (1043/1550), P<0.0001), men were
more likely to take aspirin (76% (2358) v 71% (1979),
P<0.0001), have a recorded diagnosis of hyperlipidaemia (13% (418)
v 10% (274), P<0.0001), and be prescribed lipid lowering
drugs (31% (973) v 21% (596), P<0.0001). These
differences remained despite adjustments for the practice where the
patient is registered, age, smoking status, obesity, diabetes, and hypertension.
Conclusion:
The results suggest a systematic bias
towards men compared with women in terms of secondary prevention of
ischaemic heart disease.
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What is already known on this topic
What this study adds
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Introduction |
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The UK Department of Health's publication Our
Healthier Nation outlines its aims to improve the health of the
poorest people and narrow the health gap in England.1 The
national service framework for coronary artery disease sets out the
blueprint for tackling heart disease, one of the leading causes of
death in Britain.2 It requires general practitioners to
identify all patients with ischaemic heart disease and offer
appropriate treatment to reduce their coronary risk. In secondary care,
inequalities exist in access to treatment for coronary heart disease.
There is a strong social gradient, for example, for access to coronary artery bypass grafts and angiography, with poorer patients having less
access than more affluent patients.3 Similarly, women with
angina are less likely to be referred to a specialist4 or
to have revascularisation5 than men. In secondary care, further inequalities exist between the sexes
in investigation and use
of drug treatment.
6 7
Inequalities may exist in primary care for patients with ischaemic
heart disease, although the evidence so far is limited to the
prescription of aspirin
women with angina are less likely to be
prescribed antiplatelet treatment than men.8
We aimed to determine the extent of sex inequalities in the management
of ischaemic disease in primary care using standards defined in the
national service framework for coronary artery disease.2
Our principal objective was to determine differences in the proportion
of men and women with ischaemic heart disease who are tested and
treated for hyperlipidaemia.
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Methods |
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Recruitment and ethical approval
We invited all 51 primary care groups in the Trent health
region to enter the study, of whom 19 volunteered. We asked primary
care groups to produce a list of general practices that used computer
systems compatible with MIQUEST software (EMIS/Meditel systems). We
numbered each practice and randomly selected three practices per
primary care group using the random number function on SPSS. We invited
these practices to join the study, and the first one from each group of
three to reply was recruited; if all three refused, we selected another
three practices (or as many as possible if there were fewer than three)
from that primary care group. In total, 65 practices were contacted, 24 volunteered, and 19 were recruited. One accepting practice had
inadequate diagnostic data recorded on computer, and it was excluded
from the study. Thus we recruited 18 practices. Ethical approval was
obtained for the study.
Variables
We used MIQUEST12 to extract the following data for the target population:
blockers, calcium channel blockers, lipid lowering drugs, diuretics,
and other antihypertensive drugs
Analysis
The main outcome variable was the difference in the
proportion of men and women with ischaemic heart disease taking lipid
lowering drugs. We used unconditional logistic regression to determine
differences in the recording and management of ischaemic heart disease
between men and women, simultaneously adjusting for known
cardiovascular risk factors (age, smoking status, obesity, diabetes,
hypertension). We also included a factor for the patients' general
practice in the multivariate logistic regression analysis. We performed
a subgroup analysis for patients with either a recorded myocardial
infarction or prescriptions for two or more different anti-anginal drugs.
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"First step" interventions for people with established
coronary artery disease*
Patients with established coronary artery disease should have
*As described in the national service framework for coronary artery disease2 |
blockers after a
myocardial infarction; (d) proportion of patients whose last
recorded blood pressure was under 140/85 mm Hg; (e)
proportion of men and women with diabetes who had satisfactory glucose control.
Sample size
Before the study we established that a sample of 4224 patients with ischaemic heart disease (2112 men and 2112 women) would
have a 95% power at the 0.01 significance level to detect a relative
risk of 1.5 for the use of lipid lowering drugs in men. This was based
on an exposure to lipid lowering drugs in women of 10% (pilot data).
Nineteen practices would need to be recruited to generate such a sample.
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Results |
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Study practices
The 18 practices were representative in terms of
morbidity, number of hospital admissions, and sociodemographic characteristics. Six practices had electronic links to the pathology laboratories (blood test results are posted into the patients' records automatically).
Study population
Of the 98 137 patients registered with the study
practices, 5891 (6%) had a recorded diagnosis of ischaemic heart
disease or at least one prescription for nitrate ever, or both of
these. Of the 5891 patients (2783 women) in the target group, 4326 (73%) had a Read code for ischaemic heart disease and 1565 had at
least one nitrate prescription but no Read code for ischaemic heart
disease. Of 1571 patients with a recorded diagnosis of myocardial
infarction, 1083 (69%) were men.
blockers or calcium channel antagonists.
Comorbidity and lifestyle data
Men were more likely than women to have a recorded
diagnosis of myocardial infarction (table 1). Women were more likely to
have a recorded diagnosis of hypertension, which was largely explained
by the greater proportion of women aged >75 years. No significant
differences were found between men and women for the recording of
diabetes or stroke.
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Use of aspirin and
blockers
Men were more likely to be recorded as taking aspirin
(table 3). No difference was found in the proportion of men and women
with a computer recorded contraindication to aspirin. No sex
differences were found in the proportion of patients taking
blockers in the whole population with ischaemic heart disease (table 3)
or in the subgroup of patients with a recorded myocardial infarction
(data not shown).
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Recording of fasting serum cholesterol concentration
Men were more likely to have a fasting serum cholesterol
concentration recorded (table 3); in the subgroup of practices with
electronic links for pathology results, men were still more likely than
women to have a recorded fasting serum cholesterol concentration (odds
ratio 1.8 (95% confidence interval 1.5 to 2.1); P<0.0001). This
suggests that the differences are not just a recording phenomenon but
that men are more likely to have their cholesterol concentration measured.
Diagnosis and treatment of hyperlipidaemia
Although men were more likely to have a test result
recorded, women were more likely to have an abnormal reading (fasting
serum cholesterol concentration >5 mmol/l). Despite this, men were
more likely to have a recorded diagnosis of hyperlipidaemia and to have
received lipid lowering treatment (table 3). When we restricted the
analysis to patients with a fasting serum cholesterol concentration >5
mmol/l, men were still more likely to receive lipid lowering treatment
(odds ratio 1.30 (1.08 to 1.58); P=0.0007).
Multivariate analysis
Table 4 shows the results of the multivariate analysis
to determine factors associated with having a fasting serum cholesterol
concentration recorded on computer. Men were almost twice as likely to
have this measurement recorded despite adjustments for their general
practice, age, diabetes, hypertension, obesity, and smoking status
(adjusted odds ratio 1.97 (1.67 to 2.32); P<0.0001). Similarly, men
were also more likely to receive lipid lowering drugs (1.42 (1.22 to
1.65); P<0.0001) (table 5).
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65 years.
We repeated the above analysis taking into account treatment with
blockers and aspirin in the multivariate model. Sex differences persisted despite the inclusion of these variables.
Diabetes mellitus
Patients with both ischaemic heart disease and diabetes
were more likely to be tested and treated for hyperlipidaemia than
patients without diabetes. Despite adjusting for age, men with both
diabetes and ischaemic heart disease were more likely to have their
most recently recorded blood pressure below 160/90 mm Hg (1.9 (1.3 to
2.8); P=0.001) and below 140/85 mm Hg (1.40 (1.04 to 1.97); P=0.030).
Smoking status
We found that patients aged
75 years and those recorded
as current smokers were less likely to be tested for hyperlipidaemia
(table 4). Patients aged
75 years were less likely to receive lipid
lowering drugs than younger patients (table 5). Both age and smoking
status were included as potential confounding variables, and, although
the differences were statistically significant, we need to be cautious
in how these findings are interpreted.
Patients with more severe ischaemic heart disease
The analyses were repeated for the subgroup of patients
with a diagnosis of myocardial infarction or two or more anti-anginal
drugs. These patients represent those with more severe ischaemic heart
disease. We found similar patterns both in the degree of differences
between men and women and in the significance of the analysis.
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Discussion |
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We found that among patients with ischaemic heart disease, women were less likely than men to have their risk factors (body mass index, smoking, blood pressure) recorded. Men are also more likely to have a fasting cholesterol concentration recorded. This is despite the higher consultation rates for women in general practice.13
Men were more likely to be smokers or former smokers, but women had higher rates of obesity and blood pressure readings over 140/85 mm Hg. A higher proportion of women had raised serum cholesterol concentrations. Clearly women with ischaemic heart disease in our study do not have lower risk profiles than men.
Despite this, more men take aspirin, have a diagnosis of hyperlipidaemia, and take lipid lowering drugs. These differences persist when age and other risk factors are adjusted for, and they suggest a systematic bias towards men in terms of secondary prevention of ischaemic heart disease. Our findings are consistent with the sex bias reported in studies of the management of ischaemic heart disease in secondary care. 6 7
The results of the Scandinavian simvastatin survival study and the cholesterol and recurrent events study have shown that lipid lowering treatment is clinically effective in both men and women.14 15 The national service framework for coronary artery disease does not suggest sex differences in the management of secondary prevention of ischaemic heart disease.2 We have searched the websites of Clinical Evidence, Bandolier, and the NHS Centre for Reviews and Dissemination and have found no authoritative guideline or statement recommending sex differences in management.
Strengths and weaknesses
We identified our target population from the practices'
computer system. We used powerful NHS software (MIQUEST) to collect
standardised datasets from practices and aggregate them for analysis.
We could not adjust for deprivation as the ethical considerations meant
that we were not allowed to extract strong patient identifiers, such as
postcodes. We have not been able to validate the diagnoses of ischaemic
heart disease by reference to manual records and previous
investigations (for example, exercise electrocardiography,
angiography), although validations done in previous studies show that
important discrepancies are unlikely.9 We do not think
this factor has confounded our results as the practices' diagnostic
criteria and recording accuracy would apply equally to men and women.
In addition, we performed a subgroup analysis on patients with more
severe ischaemic heart disease (defined as those with a myocardial
infarction or taking more than one anti-anginal drug), and our findings
remained unchanged. Any misclassification would have tended to
underestimate the odds ratios rather than the converse.
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Acknowledgments |
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We thank the 18 general practices that participated in the study.
Contributors: JH-C initiated the study, designed and undertook the analysis, interpreted the results, and jointly drafted the paper. MP contributed to the development of core ideas, the design, and the interpretation of the results and jointly drafted the paper. NC processed the ethical approval, recruited the practices, undertook the collection and manipulation of the data. NC and AM wrote the MIQUEST queries and contributed to the interpretation. AW contributed to the project management, the study design, and the interpretation of the results.
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Footnotes |
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Funding: Grant from the Trent regional office of the NHS Executive.
Competing interests: None declared.
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References |
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| 1. | Department of Health. Our healthier nation. London: Stationery Office, 1998. |
| 2. | Department of Health. National service framework for coronary artery disease: modern standards and service models. London: Stationery Office, 2000. |
| 3. | Hippisley-Cox J, Pringle M. Inequalities in access to coronary angiography and revascularisation: the effect of deprivation and location of primary care services. Br J Gen Pract 2000; 50: 449-454[Medline]. |
| 4. | Vogels E, Lagro-Janssen A, van Weel C. Sex differences in cardiovascular disease: are women with low socio-economic status at high risk? Br J Gen Pract 1999; 49: 963-966[Medline]. |
| 5. | Kee F, Gaffney B, Currie S, O'Reilly D. Access to coronary catheterisation: fair shares for all? BMJ 1993; 307: 1305-1307. |
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| 11. | Cannon P, Connell P, Stockley I, Garner S, Hampton J. Prevalence of angina as assessed by a survey of prescriptions for nitrates. Lancet 1988; i: 979-981. |
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| 13. | Royal College of General Practitioners. Morbidity statistics from general practice: fourth national morbidity survey 1991-2. London: HMSO, 1995. |
| 14. | Scandinavian Simvastatin Survival Group. Randomised trial of cholesterol lowering in 4444 patients with coronary heart disease: the Scandinavian simvastatin survival study (4S). Lancet 1994; 344: 1383-1389[CrossRef][Medline]. |
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Sacks FM, Pfeffer MA, Moye LA.
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(Accepted 23 January 2001)
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