High blood pressure despite treatment: Results from a cross-sectional primary healthcare-based study in southern Sweden

Abstract

Objective. To study degree of blood pressure (BP) control in primary healthcare (PHC) treated hypertensive patients in relation to sex, age, drug treatment, and concomitant diseases. Design. Random sample of patients with hypertension. Setting. Ten PHC centres in the Region of Skåne, Sweden. Subjects. All the 30- to 95-year-old patients with hypertension who during the period 12 September to 24 September 2004 attended their PHC (146 men and 229 women). Main outcome measures. Achievement of BP control (<140/90 mmHg) according to European guidelines. Results. Some 90% had been treated > 12 months, 40% had mono-therapy, 15% ≥ 3 drugs. Use of diuretics was more common in women while use of ACE inhibitors and calcium channel blockers was common in men. Inadequate BP control was related to age; only 22% had BP < 140/90 mmHg, 38% had a BP ≥ 160/100 mmHg. BP decline was inversely related to BP measured 12 months or more prior to the present follow-up (r = − 0.64, p < 0.001, for systolic and r = − 0.67, p < 0.001, for diastolic BP). The systolic or diastolic BP had in every fifth patient during treatment increased by ≥ 10 mmHg. No association was found between average BP decline and prescribed number of drugs. Conclusion. A minority of the patients had BP below the level (<140/90 mmHg) recommended by European guidelines. This study illustrates the need for continued follow-up of defined groups of patients in order to improve quality of care.

• Blood pressure control
• drugs
• family practice
• hypertension
• primary healthcare

Patients treated for hypertension should, according to European guidelines, have a blood pressure of (BP) below 140/90 mmHg; in the case of renal impairment or diabetes the upper limit is 130/80 mmHg [1–3].

The distribution of BP in patients treated for hypertension has during recent decades received only limited scientific attention [4–8]. According to the recently published report by the Swedish Council of Technology Assessment in Health Care (SBU) adequate BP reduction is in Sweden achieved in only 20–30% [9]. A similar percentage was reported from a cross-sectional study in the city of Malmö, Sweden [10].

Adequate blood pressure (BP) control is achieved in a minority of the patients treated for hypertension.

• Within primary healthcare in southern Sweden only 20% of the treated hypertensives had BP below the currently recommended target level (< 140/90 mmHg).

• No association was found between average BP decline and prescribed number of drugs.

• This study illustrates the need for continued follow-up of defined groups of patients in order to improve quality of care.

The objective of this retrospective follow-up from primary healthcare (PHC) in the Region of Skåne, Sweden, has been to study degree of BP control in patients treated for hypertension in relation to sex, age, drug treatment, and concomitant diseases.

Material and methods

Study population

The 10 PHC centres, urban and rural, are a collaborating network for studies in relation to treatment and prevention of cardiovascular disease. As the centres have not been chosen at random they cannot a priori be considered a representative regional sample. No centre had any particular organization for care of patients with hypertension. During the period 12 September and 24 September 2004, a period chosen at random, the centres were attended by a total of 381 patients diagnosed with hypertension. Number per centre ranged from 17 to 68 for staffing and demographic reasons. The representativeness of the sample has been assessed by a comparison with all the hypertensive patients who during the year 2004 had been in contact with five randomly selected regional PHC centres. No differences were found with regard to the age and sex distribution (Table I), whereas the prevalence of diabetes in the study sample was slightly higher (22.0% versus 16.8%, p = 0.004). The study was initiated by a request from the local health authorities for results illustrating the quality of care of patients treated for hypertension. For this reason no formal approval from the Ethics Committee was considered necessary.

Table I.  Comparison of the study sample (n = 380) of patients with hypertension who during a two-week study period chosen at random (12 September to 24 September 2004) attended 10 primary healthcare centres in the Region of Skåne, Sweden, and all patients with hypertension (n = 4504) who during the year 2004 had been in contact with five randomly selected PHC centres in the region.

			Age group
			30–64 years (%)	65–74 years (%)	75–95 years (%)
Study sample	Men, n	149	51 (44.0)	40 (44.0)	58 (33.1)
	Women, n	231	65 (56.0)	51 (56.0)	115 (66.9)
	Total, n	380	116	91	173
All	Men, n	1958	920 (49.9)	559 (45.1)	479 (33.7)
	Women, n	2546	924 (50.1)	680 (54.9)	942 (66.3)
	Total, n	4504	1844	1239	1421

Definition of hypertension and other risk factors

The physician-measured BP (mmHg) has been retrieved from a computerized file of records. The diagnosis of hypertension was considered established if the patient had the International Classification of Diseases (ICD)-10 code I10 to I15. Due to the retrospective design no information is available on how the BP was recorded, i.e. sitting or supine, number of recordings or time between recordings. A BP ≥140/90 mm Hg, in patients with diabetes ≥ 130/80 mm Hg, was considered non-optimal [9]. The cut-off point ≥ 160/ ≥ 100 mm Hg was in accordance with the European Society of Cardiology/European Society of Hypertension guideline [1] chosen to illustrate the number of patients having an at least 15% 10-year risk of stroke or myocardial infarction [1], [9]. History of cardiovascular disease, diabetes, smoking habits, current use of BP-lowering, lipid-lowering, or anti-diabetic medication, body weight, height, total cholesterol, creatinine, fasting blood glucose, and HbA1c was also collected from the computerized files of records. The presence of diabetes was defined as ICD10 code E10–E14 and history of cardiovascular disease as I20–I77.

Statistical methods

SPSS (version 10.0) was used for all statistical analyses. Change in BP during treatment was defined as the difference in diastolic and systolic BP, respectively, between the examination in September 2004 and values recorded 1–2 years prior to follow-up. A scatter-plot was used to illustrate change in diastolic BP and systolic BP, respectively; associations were expressed as the correlation coefficient (r). Differences in age- and sex-adjusted change in BP between PHCs were calculated using an analysis of covariance (ANCOVA) model.

Results

Baseline characteristics

Five patients were excluded due to missing values on actual BP (n = 4) or age (n = 1). Mean age was 70.8±12.7 years, 60% were women (Table II). One out of 10 had been diagnosed within the last 12 months, 57% more than 5 years ago. Some 10% were smokers; one out of five had diabetes. History of cardiovascular disease was reported by 6% of the patients aged 30–64 years and by 26% in the oldest age group (75–95 years). Lipid-lowering treatment had been prescribed for 20% of the patients.

Table II.  Distribution of biological, lifestyle factors, and present lipid- and blood pressure-lowering medications among 376 patients with hypertension who during a two-week study period chosen at random (12 September to 24 September 2004) attended 10 primary healthcare centres in the Region of Skåne, Sweden.

	Age groups
	30–64 years	65–74 years	75–95 years	All subjects
Number of subjects	112	91	173	376
No of men,%	43.8	44.0	33.5	39.1
Age, years	54.5±7.8	70.3±2.6	81.5±4.7	70.8±12.7
Duration of hypertension*
< 1 year,%	18.6	6.0	9.6	11.3
1–5 years,%	29.9	42.2	27.4	31.8
> 5 years,%	51.5	51.8	63.1	57.0
Systolic BP, mmHg	145±18	152±20	157±21	152±21
Diastolic BP, mmHg	85±9	80±10	80±10	82±10
BP ≥ 140/90 mmHg,%	67.9	79.1	83.7	77.9
Systolic BP ≥ 140 mmHg,%	63.4	79.1	83.2	76.3
Diastolic BP ≥ 90 mmHg,%	32.1	19.8	21.5	24.3
BP ≥ 160/100 mmHg,%	25.9	37.4	45.1	37.5
Current anti-hypertensive drugs
Median number of drugs	1.5 (0–4)	1.6 (0–4)	1.7 (0–4)	1.6 (0–4)
Without drugs,%	11.6	8.8	5.8	8.2
Monotherapy,%	40.2	37.4	40.5	39.6
Combination of 2 drugs,%	35.7	38.5	36.4	36.7
Combination of ≥ 3 drugs,%	12.5	15.4	17.3	15.4
Fasting glucose, mmol/L	6.3±2.4	6.3±2.2	6.2±1.6	6.3±2.0
Diabetes,%	19.6	29.7	20.2	22.3
HbA1C,% (among diabetics)	7.1±1.7	6.0±0.7	6.0±0.7	6.2±1.1
BP ≥ 130/80 mmHg,% (among diabetics)	100	88.0	97.1	95.1
History of cardiovascular disease,%	6.3	23.1	26.0	19.4
Current smokers,%	22.4	6.8	9.5	12.7
Former smokers,%	11.5	24.5	18.4	17.9
Total cholesterol, mmol/L	5.4±1.0	5.4±1.0	5.2±1.0	5.3±1.0
Use of lipid-lowering drugs,%	17.0	33.0	17.9	21.3
Body mass index, kg/m^2	30.0±4.6	30.1±5.6	26.8±3.8	28.6±4.8
s-creatinine, mmol/L	71.8±17.8	79.4±18.7	89.2±32.9	81.8±27.1

BP = blood pressure. *Information on duration of hypertension was not available in 39 patients. Data are presented as mean (SD), as proportions, or as median (range).

Use of antihypertensive drugs and BP level

Some 8% were on non-pharmacological treatment. The median number of drugs was 1.6. Four out of 10 patients had monotherapy, 40% had diuretics, 32% beta-blockers, 15% calcium channel blockers, 9% angiotensin converting enzyme (ACE) inhibition, and 4% angiotensin-II receptor antagonists. Combination treatment with two drugs was used in 37%; three or more drugs were used by 15%. Number of drugs used was similar in men and women. Treatment with diuretics was, however, more common in women (62% versus 41%, p < 0.001), and calcium channel blockers and ACE inhibition were more common in men (39% versus 26%, p = 0.017, and 25% versus 16%, p = 0.035, respectively). In 75% of the men and 80% of the women the systolic BP was ≥ 140 mmHg, the diastolic BP ≥ 90 mmHg or both. A total of 40% of the men and 36% of the women had BP ≥ 160/100 mmHg (see Table II). The proportion of patients having BP ≥ 140/90 increased from 68% among patient younger than 65 years to 84% in the oldest age group (≥75 years). The corresponding percentages with BP ≥ 160/100 mmHg in these two age groups were 26% and 45%, respectively. Adequate control of the diastolic BP was in all age groups, in both men and women, more common than adequate control of the systolic BP.

Relation between previous and current blood pressure

Information on previous BP was for different reasons not available for 148 patients, thus the analysis is based on 228 patients (Table III). This sample was, in terms of sex distribution, median number of anti-hypertensive drugs, prevalence of diabetes, and cardiovascular disease and the percentage having reached the recommended BP goal, similar to the entire sample of patients (see Table II).

Table III.  Present and previous blood pressure among 228 treated (for at least 12 months) patients with hypertension.

	Age groups
	30–64 years	65–74 years	75–95 years	All subjects
Number of subjects	64	59	105	228
No of men,%	43.8	44.1	33.3	39.0
Duration of hypertension
1–5 years,%	39.1	52.5	30.5	38.6
> 5 years,%	60.9	47.5	69.5	61.4
Number of anti-hypertensive drugs	1.6 (0–4)	1.8 (0–4)	1.8 (0–4)	1.7 (0–4)
Diabetes,%	20.3	35.6	22.9	25.4
History of cardiovascular disease,%	6.3	25.4	22.9	18.7
Current blood pressure, mmHg
Systolic BP	143±15	148±18	154±20	150±19
Diastolic BP	84±8	79±10	80±10	81±10
BP ≥ 140/90,%	64.1	74.6	82.9	75.4
Previous blood pressure, mmHg
Systolic BP	157±21	162±21	163±21	161±21
Diastolic BP	92±11	86±11	84±10	87±11
BP ≥ 140/90,%	89.1	91.5	94.3	92.1

Previous blood pressure was defined as blood pressure value recorded at least one year earlier than the present follow-up. BP = blood pressure. Data are presented as mean (SD), as proportions or as median (range).

There was in all age groups a significant decline in the mean BP (−11 mmHg (95% CI −14 to −8 mmHg) for systolic BP and −6 mmHg (95% CI −8 to −5 mmHg) for diastolic BP). The range for change in systolic and diastolic BP was –40 to +40 mmHg and −75 to +54 mmHg, respectively (Figure 1). There was a significant relationship between BP decline and BP 12 months or more prior to the present follow-up (r = − 0.64, p < 0.001, for systolic BP and r = − 0.67, p < 0.001, for diastolic BP). Many patients were still found to have very high pressures: an increase during treatment of at least 10 mmHg or more was observed in every fifth patient. Figure 2 shows that in each age group the magnitude of BP change was almost identical. Similarly, there were no major differences in magnitude of BP change between groups using one, two, or three or more drugs (Figure 3).

Figure 1.  Relationship between change (in mmHg) in diastolic blood pressure (BP) (upper panel) and systolic blood pressure (lower panel) and BP recorded at least one year prior to the present follow-up. The regression prediction line (with 95% confidence interval) and r-square value are depicted in the figure.

Figure 2.  Boxplot showing mean change (95% confidence interval) of diastolic (upper panel) and systolic (lower panel) blood pressure (BP) in age groups at present follow-up. Change in BP (in mmHg) was calculated as the difference between present BP and BP recorded at least one year prior to the present follow-up.

Figure 3.  Boxplot showing mean change (95% confidence interval) of systolic blood pressure (BP) in relation to number of BP-lowering drugs. Change in BP (in mmHg) was calculated as the difference between present systolic BP and systolic BP recorded at least one year prior to the present follow-up.

Discussion

The present study illustrates the feasibility of using a retrospective approach to assess change in pressure and degree of blood pressure control in patients being treated for hypertension. It is concluded that only about 20% of the patients had BP below the currently recommended target level [1–3]. This estimate is in line with results in previous surveys [4], [5], [8–10].

Absence of current national guidelines

An appropriate question is, of course, why so many – despite treatment – continue to be exposed to BP above the recommended level of 140/90 mmHg. Absence of current national guidelines for treatment of hypertension could be a contributing factor. An alternative explanation could be that the recommended target pressure according to the European guidelines [1], [11] is considered by many physicians in Sweden to be too low and that the achieved BP should be considered in relation to a global assessment of the patient's predicted cardiovascular risk [1], [11–13].

Awareness of treatment results

None of the 10 centres involved had any prior knowledge of their treatment results. Neither patients nor the Regional Board of Health and Welfare make any regular attempts through questions or surveys to assess treatment results. Hence, there are no premises for allocation of economic resources based on the quality of care.

Compliance with treatment

There may be marked differences in the achieved BP reduction between patients prescribed the same drug and dose. Patients’ attitude to treatment, age and education [14], occurrence of side effects, and concomitant diseases are some of the circumstances that may modify their compliance with treatment [15–18]. Inadequate lowering of the BP should hence make the doctor focus on these potential reasons, and on measures to improve the degree of BP control. It has been estimated that as many as 50% discontinue therapy by the end of the first year [19]. A rational approach could be to study compliance in relation to relevant patient circumstances and conditions in order early on to identify groups that are the most and least likely to cope with the prescribed mode of treatment.

Blood pressure reduction in relation to number of drugs

The median number of drugs prescribed per patient ranged from one to two. Only 1 patient out of 12 was prescribed 3 or 4 different drugs. No association was found between the achieved average BP decline and the prescribed number of drugs. This finding is in agreement with previous publications from the Swedish PHC [8]. There was no association either with the drug of treatment. The relative absence of combinations of drug treatment should, however, also be considered in relation to the recommended need for a global cardiovascular risk assessment [11]. Further studies are needed to assess the prevalence and treatment of other risk factors in patients with adequate BP control at the time of follow-up [9].

Prescription of drugs and gender differences

Some 62% of the female patients as opposed to only 41% of the men were treated with diuretics. The use of calcium channel blockers and ACE inhibitors was more common in men than in women. Further studies are needed to improve our understanding of patterns of prescription, e.g. who is treated with what and why.

Trends of morbidity and mortality in diseases related to high blood pressure

During the last decades there has been a decline in the incidence of and mortality from myocardial infarction [20], [21]. The trend for stroke is, however, the reverse in Sweden: in both men and women and in all age groups the incidence is going up [22], [23]. Whether this may be related to a growing proportion of subjects being exposed to high BP or be due to inadequate BP treatment [10] remains to be evaluated. In this present study the relative absence of adequate BP reduction in patients with hypertension is similar in men and women and in all age groups.

Benefits for patients versus benefits for populations

In treating patients with hypertension, with regard to the benefits, one should make a distinction between the single patient and the population with hypertension. From a public health point of view the objective is to reduce the morbidity and mortality in the society at large related to atherosclerotic diseases [2]. As high BP is only one of several modifiable risk factors for atherosclerotic disease there are a number of alternative options. It has been estimated that smoking and diabetes approximately double the risk for stroke in a cohort with hypertension [10]. The treatment goal for patients with hypertension should hence not only be defined in terms of mmHg but rather in terms of lowering the risk of stroke and myocardial infarction [11], [24].

Limitations of the study

No information is available on how BP was recorded in each case. It remains to be evaluated whether and how this could have influenced the distribution of the measured BP in the study. The procedure for selecting the PHCs, the study population with hypertension and diabetes [25] (i.e. hypertensive and diabetes treatment in the absence of established diagnosis did not qualify as inclusion criteria in the study group), the retrieval procedure for patients diagnosed with hypertension, the limited number of patients, and the lack of a global assessment of cardiovascular risk for each patient are other study limitations with a potential influence on the results.

The present study supports previous studies concluding that adequate BP control is achieved in a minority of the patients treated for hypertension. This observation illustrates the need for continued follow-up of patients in relation to predefined treatment goals and the need for studies that can improve our understanding of conditions and circumstances that have an influence on quality of care.