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Journal of the New Zealand Medical Association, 19-February-2010, Vol 123 No 1309

Are at-risk New Zealand women receiving recommended cardiovascular preventive therapy?

Olivia Bupha-Intr, Sally B Rose, Beverley A Lawton, C Raina Elley,
Simon A Moyes, Anthony C Dowell

Abstract

Aim To determine whether use of cardiovascular medications by a sample of mid-life and older women is consistent with New Zealand cardiovascular risk guidelines.

Method Retrospective analysis of risk factor data collected during the Women’s Lifestyle Study involving 1089 40–74 year old women. Outcome measures included: 5-year cardiovascular (CVD) risk score calculated using the adjusted Framingham equation and self-reported use of cardiovascular medications.

Results Seven percent (76/1089) of women had established CVD, and a further 3% (33/1089) had a risk score greater than 15% (high risk). Of the 109 women at high risk (risk score ≥15% or established CVD); 36% (39/109) were taking aspirin, 55% (60/109) were taking blood pressure-lowering medication, 45% (49/109) were taking lipid-lowering medications and 17% (19/109) were taking all three medications. Triple therapy was being taken by 12% of women (4/33) for primary prevention (5-year risk score ≥15%) and only 19.7% of women for secondary prevention (15/76).

Conclusion These results suggest that women at high-risk are not receiving cardiovascular medications as recommended by the guidelines, reflecting a ‘treatment gap.’ Modifiable barriers to the management of women at risk for CVD need to be identified and addressed to reduce cardiovascular morbidity and mortality among women.

Cardiovascular disease (CVD) is the leading cause of premature death and disability in New Zealand for both men and women, accounting for 40% of all deaths.1 Although age-standardised deaths from coronary heart disease (CHD) are higher among men than women, deaths from all CVD (including CHD, hypertensive disease and cerebrovascular disease) are higher among women than deaths from all forms of cancer.1 The New Zealand cardiovascular risk guidelines were developed with the intent to systematically assess and manage the population at risk for CVD.2

Absolute risk-based approaches to CVD event prediction have been shown to be better than the traditional, single risk factor approach.3 The guideline recommendation is that any individual identified with a five-year cardiovascular risk of greater than or equal to 15% should be offered pharmacological intervention consisting of low dose aspirin, blood pressure-lowering medication and a lipid-lowering medication (sometimes referred to as combination or ‘triple therapy’).4 Use of triple therapy has been shown to halve the absolute risk of having a cardiovascular event.5–7

Despite the considerable potential for risk reduction, past research suggests that those at highest risk of cardiovascular disease are not receiving treatment recommended by the CVD guidelines.8 9-12 For example, analysis of primary care visits by men aged 45 and older, and women aged 55 and older in 2000 showed that only 28% of those with cardiovascular disease were taking a combination of blood pressure and lipid-lowering medication.8 Among a cohort of 29,000 patients with type 2 diabetes, two thirds of patients with cardiovascular disease and 44% of those at high risk were taking appropriate CVD treatment.10

A recent audit of data collected for 621 patients undergoing CVD risk assessment at a nurse clinic showed that 59% of patients with previous cardiovascular disease were taking triple therapy when first assessed, and this increased to 71% (51/72) at a follow-up assessment.12

Medication use in relation to cardiovascular risk has not been reported separately for men and women in past New Zealand research, so it is not clear to what extent, if at all, the treatment gap exists for women. There is also some controversy about the use of cholesterol lowering medication (particularly statins) for cardiovascular risk reduction in women,13 with evidence from secondary prevention (but not primary prevention) trials showing that statins reduce the risk of cardiovascular events in women.6

Primary prevention trials have been limited to men, and it has been argued that women respond differently to men and may not therefore benefit from statin use to the same extent.14 15 Despite the different levels of evidence for the efficacy of cardiovascular treatment for men and women, the cardiovascular treatment guidelines do not differentiate between men and women (except as a marker for absolute risk). The present study was therefore conducted to determine whether women with a 5-year cardiovascular risk of greater than or equal to 15% are being treated with triple therapy in line with guideline recommendations. Given the debate surrounding the use of statins for cardiovascular risk reduction in women, we also sought to investigate uptake of lipid-lowering agents for secondary disease prevention.

Methods

Participants—1089 women aged 40-74 years recruited through 17 general practices in the greater Wellington region for the Women’s Lifestyle Study between 2004 and 2005.16 17 Women were identified through General Practice registers and invited to attend a screening interview for a ‘lifestyle study’. Women were eligible for randomisation to an intervention (enhanced Green Prescription) or control (Usual care) if deemed physically inactive (self-reported undertaking less than 150 minutes of at least moderate intensity physical activity per week), and medically able to increase their activity levels.

Data collection—Data were collected in face to face interviews with a research nurse and included: demographics (age, ethnicity, NZ Deprivation score,18 highest education level), cardiovascular risk factor information (blood pressure and cholesterol measurements, diabetes and smoking status), family history of coronary heart disease or ischaemic stroke, past history of cardiovascular disease and current use of cardiovascular medications (aspirin, blood pressure-lowering and lipid-lowering medications). Participants attended a baseline visit (Time 1) and 2 subsequent annual visits (Time 2 and Time 3).

Calculating cardiovascular risk—A 5-year cardiovascular risk score was calculated using the adjusted Framingham risk equation for individuals with no previous cardiovascular history.19 The risk score estimates the probability of having a cardiovascular event (including ischaemic heart disease, cerebrovascular disease or peripheral arterial disease) in the next 5 years. Variables required for the equation are sex, age, systolic blood pressure, smoking, total cholesterol, HDL, diabetes, and ECG left ventricular hypertrophy (LVH). For the purposes of this study the ECG LVH was set at zero. Individuals with a cardiovascular history were classified as greater than 20% cardiovascular risk over the next 5 years as per the guidelines.2 At the time of the study, the New Zealand CVD guidelines recommended a 5% upward adjustment of risk level for any individual with:

A family history of premature coronary heart disease or ischaemic stroke in a first degree male relative before the age of 55 years or a first degree female relative before the age of 65 years
Māori, Pacific peoples or people from the Indian subcontinent
Both diabetes and microalbuminaemia
Type II diabetes for more than 10 years or who have an HbA1c consistently greater than 8%
The metabolic syndrome
These adjustments should be made only once for people who meet more than one criteria (the maximum adjustment is 5%).

Cardiovascular risk scores were calculated as described above and scores moved up one risk category (5%) as per the guidelines. Our study was limited in risk adjustment due to lack of data for some of the adjustment criteria:

The gender of siblings was not recorded when asked about family history of cardiovascular disease so we used a premature history in a sibling before the age of 60 years to estimate the risk
There was no data collected from the individuals about microalbuminaemia, the metabolic syndrome or HbA1c levels
The ethnicity data were grouped into five categories; New Zealand European, Māori, Pacific, Asian or Other. It is unclear which grouping peoples from the Indian subcontinent associated with so adjustment for Indian ethnicity was not possible

Cardiovascular medications—Cardiovascular medications were grouped as follows:

Antiplatelet agents
Blood pressure-lowering agents
Lipid-lowering agents

Participants were asked if they were currently taking any medications in each of the above categories. Individuals with a risk score of 15% or higher were assessed to determine whether they were taking medications as per the guidelines.

Outcome measures—Cardiovascular risk scores (grouped into the following categories: <10%, 10-14% and ≥15%, and ≥20%) and use of cardiovascular medications ascertained in relation to guideline recommendations.

Analyses— Proportions with high cardiovascular risk, and on medications in each risk category, were calculated for ethnic and socioeconomic subgroups. Odds ratios and p-values were calculated by constructing logistic regression models containing age, ethnicity and deprivation (socioeconomic status) using SAS 9.1.3.

Results

Table 1 displays the demographic and risk factor characteristics of the sample when first assessed (Time 1). The majority of women in the sample were aged between 50-64 years (mean age 58.9, SD 6.9). This was not a population based sample, but purposive recruitment of Māori and Pacific women resulted in the proportion of women in these ethnic groups being comparable to that of the census for women in the 50–65 year age-band.20

Cardiovascular risk profile—Not all participants attended all three study visits, and some of those who attended did not have their fasting blood test carried out, so full data were not available on all participants at all time points. Five-year cardiovascular risk scores were calculated for 1050 women (97% of the 1089 participants) at enrolment into the Women's Lifestyle Study (Time 1). Risk scores were calculated for 974 women (89%) at 12 months (Time 2) and 946 women (87%) at 24 months (Time 3). Table 2 presents the adjusted Framingham CVD risk scores stratified by age, ethnicity and deprivation for 1050 women at Time 1.

Table 1. Demographic and risk factor profile of 1089 participants in the Women’s Lifestyle Study (figures are n (%) unless otherwise denoted)

Characteristics	n	%
Age band
40-44	31	3
45-49	36	3
50-54	269	25
55-59	291	27
60-64	223	20
65-69	169	16
70+	70	6
Ethnicity
NZ European	846	78
Māori	111	10
Pacific	30	3
Asian	29	3
Other	71	7
Not stated	2	0
NZ Deprivation
Low (least deprived scores 1-3)	477	44
Medium (scores 4-7)	358	33
High (most deprived, scores 8-10)	162	15
No score available	92	8
Health measures
Smoker	141	13
Diabetes	61	6
Previous CVD*	76	7
Family History of CVD	330	30
BMI (kg/m2) mean, SD	29.15	5.90
Systolic BP (mmHg) mean, SD	124.37	18.07
Diastolic BP (mmHg) mean, SD	74.24	9.62
Total Cholesterol (mmol/L) mean, SD	6.07	1.06
HDL (mmol/L) mean, SD	1.69	0.44

* Previous CVD includes: Heart attack (n=21), Angina (n=43), CABG (n=14), Stroke (n=21).

The majority of women were low-risk with scores less than 10% (80%), and 33 women (3%) had calculated CVD risk scores of ≥15% (no previous CVD). Seven percent of women (76/1050) self-reported previous cardiovascular disease. Ten percent of women overall were classed as high-risk including those with established CVD and a risk score ≥15% (109/1050). Nineteen percent of Māori women were at high risk compared with 9% of European women in the study (p<0.001). Māori women in the study were significantly more likely to be at high risk than non-Māori women (odds ratio: 4.0 (95% CI: 2.05 to 7.8)), after adjusting for age and socioeconomic status.

While 7.5% of the women in the least deprived category were at high risk, 14.4% and 12.7% were at high risk among women in the moderate and high deprived categories, respectively (p=0.01).

When including only those participants for whom data were available at all three assessment periods (n=902), the proportion of women at high risk for cardiovascular disease (calculated score ≥15% or established CVD) increased over time.

Table 2. Adjusted CVD risk scores for 1050 women at Time 1 stratified by age, ethnicity and NZ Deprivation band

Characteristics	Total	5 Year CVD risk <10%		5 Year CVD risk 10-14%		5 Year CVD risk ≥15%*		Established CVD >20%		All high risk ≥15%**
Age band	n	n	%	n	%	n	%	n	%	n	%
40-44	26	24	92.3	2	7.7	0	0.0	0	0.0	0	0.0
45-49	26	19	73.1	4	15.4	1	3.8	2	7.7	3	11.5
50-54	258	233	90.3	6	2.3	2	0.8	17	6.6	19	7.4
55-59	289	247	85.5	20	6.9	3	1.0	19	6.6	22	7.6
60-64	218	169	77.5	26	11.9	8	3.7	15	6.9	23	10.6
65-69	165	108	65.5	33	20.0	8	4.8	16	9.7	24	14.5
70+	68	37	54.4	13	19.1	11	16.2	7	10.3	18	26.5
Ethnic group
NZ European	829	676	81.5	75	9.0	22	2.7	56	6.8	78	9.4
Māori	94	62	66.0	14	14.9	4	4.3	14	14.9	18	19.1
Pacific	27	21	77.8	2	7.4	4	14.8	0	0.0	4	14.8
Asian	29	21	72.4	5	17.2	1	3.4	2	6.9	3	10.3
Other	69	56	81.2	7	10.1	2	2.9	4	5.8	6	8.7
not stated	2	1	50.0	1	50.0	0	0.0	0	0.0	0	0.0
Deprivation band
Least deprived (scores 1-3)	468	391	83.5	42	9.0	11	2.4	24	5.1	35	7.5
Medium (4-7)	341	253	74.2	39	11.4	14	4.1	35	10.3	49	14.4
Most deprived (scores 8-10)	150	113	75.3	18	12.0	6	4.0	13	8.7	19	12.7
Not known	91	80	87.9	5	5.5	2	2.2	4	4.4	6	6.6
Total	1050	837	79.7	104	9.9	33	3.1	76	7.2	109	10.4

* Individuals with a calculated 5yr CVD risk ≥15% (without established CVD)

** Individuals considered as high risk as per NZGG guidelines (includes those with previous CVD, and those with a calculated 5-year CVD risk ≥15%)

Use of cardiovascular medications—At the first study visit (Time 1), 9% of women (96/1089) were taking aspirin, 25% (269/1089) were taking blood pressure-lowering medication, 13% (138/1089) were taking lipid-lowering medication and only 3% (29/1089) were taking all three medications. Figure 1 depicts the use of cardiovascular medications by women in relation to CVD risk scores at Time 1. Of 109 women at high risk (established cardiovascular disease or a calculated 5-year CVD risk score greater than 15%), the proportion taking the recommended medications was low; 36% (39/109) were taking aspirin, 55% (60/109) were taking blood pressure-lowering medication, 45% (49/109) were taking a lipid-lowering agent and 17% (19/109) were taking all three medications.

At Time 1, women with established CVD clearly had the highest uptake of cardiovascular medication, with 55% taking blood pressure medications (42/76), 47% taking lipid-lowering medication (36/76), 42% taking aspirin (32/76) and only 20% taking all three therapies (15/76). Those women without established CVD but with a calculated risk score greater than 15% had relatively low uptake of the recommended medications, with only 12% taking all three therapies (4/33). The proportions taking cardiovascular medications were similar across different ethnic groups after adjusting for age and socioeconomic status (p=0.5).

Figure 1. Use of cardiovascular medications by 1050 women at Time 1 in relation to CVD risk scores

Use of lipid-modifying medications—109 women were classified as high risk at Time 1 (76 had established CVD, 33 had a calculated score of at least 15%), with 45% taking lipid-lowering medication (49/109). The remaining 55% (60/109) of those who met the guideline criteria were not taking lipid-lowering medication for secondary prevention at the time of the interview, representing a ‘treatment gap’. The proportions of women in the high-risk category taking lipid-lowering medications were similar across ethnic groups at Time 1 after adjusting for age and socioeconomic status (p=0.9), with 44% of Māori women at high risk taking lipid-lowering medications and 45% of New Zealand European women.

Table 3 shows use of cardiovascular medications by women at high risk for CVD stratified by ethnic group over time. Use of aspirin was not recorded at Time 2 and 3, so use of triple therapy could not be determined beyond Time 1. The proportion of women taking blood pressure and lipid-lowering medications did not differ significantly over time. Our results suggested that Māori women at high cardiovascular risk (>15% or previous CVD) in the study were more likely to be on triple cardiovascular treatment than non-Māori women at high risk (odds ratio: 2.28 (95% CI: 0.6 to 9.2) after adjusting for age and socioeconomic status, although this result did not reach statistical significance, possibly due to the small numbers involved.

Table 3. Medications taken by women at high risk for CVD (5-year risk ≥15%, and established CVD) over time presented by Ethnic Group

Year	Ethnic group	Total high-risk	BP lowering		Lipid lowering		Combined BP and lipid lowering		Triple therapy
Year	Ethnic group	n*	n	%	n	%	n	%	n	%
2004 to 2005	NZ European	78	44	56.4	35	44.9	20	25.6	12	15.4
	Māori	18	10	55.6	8	44.4	7	38.9	5	27.8
	Other**	13	6	46.2	6	46.2	4	30.8	2	15.4
	Total (Time 1)	109	60	55.0	49	45.0	31	28.4	19	17.4
2005 to 2006	NZ European	65	41	63.1	34	52.3	25	38.5	Data not available***
	Māori	13	7	53.8	6	46.2	5	38.5
	Other	10	6	60.0	5	50.0	4	40.0
	Total (Time 2)	88	54	61.4	45	51.1	34	38.6
2006 to 2007	NZ European	60	38	63.3	33	55.0	24	40.0	Data not available***
	Māori	9	4	44.4	3	33.3	3	33.3
	Other	7	3	42.9	4	57.1	3	42.9
	Total (Time 3)	77	45	58.4	40	51.9	30	39.0

* Includes only those for whom complete data were available at each assessment.

** Ethnic groups other than NZ European and Māori were collated due to the small sample size (includes Pacific, Asian and Other ethnicities).

*** Data on aspirin were not collected at Times 2 and 3.

Discussion

This research suggests that there is a significant treatment gap between the New Zealand cardiovascular risk guideline recommendations and clinical practice for women at risk for cardiovascular disease. Over 80% of women meeting the cardiovascular guideline criteria for combined cardiovascular treatment (aspirin, BP-lowering and lipid modifying medications) were not taking all three. Of particular concern was the proportion of women with established cardiovascular disease (80%) who were not receiving the recommended triple therapy (61/76).

Consistent with existing knowledge, we found Māori women in the study to have higher rates of established cardiovascular disease compared with non- Māori.9 11 Encouragingly, there was no evidence of disadvantage in use of medication by ethnicity, with both Māori and non- Māori having the same rate of cardiovascular medication use, which is consistent with past research.9 11

Comparison with other studies—This cardiovascular treatment gap has been identified in past research that has included, but not separately reported on, the use of cardiovascular medication by women at risk.8 10 9 11 The proportion of at-risk women in our study receiving triple therapies was lower than found for males and females in previous studies (17.4% of all high-risk women, and 20% for secondary prevention at Time 1). Riddell et al reported use of triple therapy by 48% of Māori and 44% of non- Māori for secondary prevention9 and Peiris et al found that 50% of high-risk patients were receiving all three recommended therapies.11

Rafter et al found that 28% of patients were taking blood pressure and lipid-lowering medications for secondary prevention but their sample included both men and women.8 These cardiovascular ‘treatment gaps’ are not limited to New Zealand, research in the USA and United Kingdom has demonstrated similar findings for statin use for secondary prevention, with up to 88% of patients with coronary artery disease not taking statins in a US study,21 and only 13% of men and 8% of women with ischemic heart disease prescribed statins in a UK study.22

Although New Zealand has been a world leader in absolute risk based guidelines,23 uptake has been variable within primary care. The reasons for this are likely to be multiple and complex, involving a range of barriers to assessment and management of CVD risk at the health system, doctor and patient level. For example, surveys of family physicians in the United States suggest that cost of medications, side effects, knowledge and skills to recommend lifestyle changes and to facilitate patient adherence, time for counselling, and adherence to medications are significant barriers to CVD risk management.24 25

Furthermore, divided clinical opinion about the appropriateness of cholesterol lowering medication for women26 27 is likely to play a contributing role. Likewise the ongoing debate over whether aspirin reduces coronary heart disease events in women may also have contributed to the lack of uptake of the guidelines.28 Since this study was completed, a meta-analysis of primary prevention trials involving aspirin has been published and the results suggest that routine aspirin is not justified for primary prevention of coronary heart disease.29

Strengths and limitations—This is one of the first studies to describe cardiovascular medication use in relation to cardiovascular risk among a large sample of New Zealand women that includes good participation by both Māori and Pacific participants. Although not a representative sample, eligibility criteria for the Women’s Lifestyle Study was being ‘physical inactive’, therefore women in the present study might be expected to have higher overall risk profiles than women of this age group in the general population. Limitations of this study are that we are unable to determine the reasons for the ‘treatment gap’.

Medication data were based on self-report, and not checked against prescriptions, and it is unclear whether individuals had been offered the medication but declined to take it, or if there was a contraindication or previous adverse reaction to the medication. If so our treatment gap may have been overestimated. Likewise, previous cardiovascular events were self-reported not based on medical records, so the number of women with established cardiovascular disease may be over or under-reported here.

Conclusions

The low uptake of recommended medications by women who are at high risk of cardiovascular disease indicates there are still substantial gaps in the use of evidence based guidelines in clinical practice. Modifiable barriers to the successful management of women at risk for cardiovascular disease need to be identified and addressed to reduce cardiovascular related morbidity and mortality.

Competing interests: None known.

Author information: Olivia Bupha-Intr, 4th Year Medical Student, Department of Primary Health Care & General Practice, University of Otago, Wellington; Sally B Rose, Senior Research Fellow, Women’s Health Research Centre, Department of Primary Health Care & General Practice, University of Otago, Wellington; Beverley A Lawton, Director, Women’s Health Research Centre, University of Otago, Wellington, Department of Primary Health Care & General Practice; C. Raina Elley, Senior Lecturer, Department of General Practice & Primary Health Care, School of Population Health, University of Auckland, Auckland; Simon A Moyes, Statistician, Department of General Practice & Primary Health Care, School of Population Health University of Auckland, Auckland; Anthony C Dowell, Professor, Department of Primary Health Care & General Practice University of Otago, Wellington

Acknowledgement: We thank the National Heart Foundation of New Zealand for funding this summer studentship project.

Correspondence: Beverley Lawton, Women's Health Research Centre, Department of Primary Health Care and General Practice, University of Otago, P O Box 7343 Wellington South, New Zealand. Fax: 04 385 5473; email: bev.lawton@otago.ac.nz

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