Obesity and Hypertension

High Body Weight is associated with an increasing Prevalence and Lack of Control of Obesity-Hypertension

Bramlage P. (1,2), Wittchen H.-U. (1), Pittrow D. (3), Kirch W. (3), Lehnert H. (4), Höfler M. (5), Unger T. (6), Sharma A. M. (7)

(1) Technical University of Dresden, Institute of Clinical Psychology and Psychotherapy, (2) Sanofi-Synthelabo GmbH, Berlin, (3) Institute of Clinical Pharmacology, Technical University, Dresden (4) Department of Endocrinology and Metabolism, University of Magdeburg, (5) Max-Planck Institute of Psychiatry, Munich, (6) Department of Pharmacology, Charité Berlin. (7) Franz Volhard Clinic-Charité, Berlin, Germany

Current address of corresponding author: Dr. Peter Bramlage, MD Institute of Clinical Psychology and Psychotherapy Technical University of Dresden Chemnitzerstrasse 46, D-01187 Dresden, Germany Tel: +49 351 4633 6985, Fax: +49 351 4633 6984 E-Mail: [email protected]

ABSTRACT Context Hypertension is largely uncontrolled in primary care and obesity is closely associated with higher blood pressure readings. Lack of data on the prevalence, treatment and control of obesity-hypertension in primary care. Objective To assess 1) blood pressure readings according to BMI in primary care in a representative survey of German primary care physicians, 2) the prevalence of hypertension in these patients, and 3) the diagnosis, treatment status and control rates of hypertension in obese patients as compared to patients with normal weight. Methods Cross-sectional point prevalence study of 45,125 unselected consecutive primary care attendees in a representative nationwide sample of 1,912 primary care settings. Main Outcome Measures Blood pressure readings in normal and overweight primary care attendees, prevalence of hypertension in obesity, treatment and control rates of hypertension according to BMI classes. Results Overall prevalence of hypertension in normal weight is 34.25 %, in overweight it is 60.84 %, grade 1 obesity 72.86 %, grade 2 obesity 77.12 %, and grade 3 obesity 74.14 %. But while hypertension is more frequently detected in overweight patients, the discrepancy between the number of treated and the number of controlled patients is also increasing with increasing weight. Conclusions: The increasing prevalence of hypertension and the decrease in control-rates documents the specific challenges that hypertension-control imposes in obese patients. Therefore is seems necessary to further investigate the reasons for poor control and question. Specific recommendations for treatment of hypertension in the obese should be issued.

Bramlage et al. Prevalence of Obesity-Hypertension

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INTRODUCTION Overweight and obesity have been recognized to be a major public health issue in most areas of the world [1]. For the US (1999-2000) Flegal et al. reported a prevalence of 64.5 % for overweight (BMI > 25 kg/m2) and 30.5 % for obesity (BMI > 30 kg/m2) [2]. In Germany the prevalence is somewhat lower albeit still high with 59.7 % of the German population being overweight and about 20.3 % obese [3]. Compared to prevalence data gathered in the early 90ies this represents a substantial increase and contributes considerably to the expenditure of health care [4]. There is a considerable amount of comorbidity in obese patients. Hypertension is one of the most important components that severely aggravate the further course of the disease. Among the patients with obesity, prevalence of hypertension is high having been reported to be around 50 % [5]. It increases with higher grades of obesity [6]. On the other hand, obesity is almost the rule among patients with hypertension with almost 70 % of hypertensive patients being overweight [7]. At the same time, early detection , treatment and its stringent control continues to be a problem in primary care, despite the fact that hypertension is a pivotal determinant of cardiovascular complications such as coronary heart disease, stroke, or renal insufficiency in obese patients and the protective effect of antihypertensive therapy well established [8, 9]. Probability of insufficient blood pressure control in obese patients is 50 % higher than in hypertensive patients with normal weight (BMI 18.5 – 24.9 kg/m2) [10]. Albeit the primary care system is the first step for most obese and hypertensive people into the health care system, little is known about the prevalence of hypertension in obese primary care attendees.


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Data on the particular challenges of primary care physicians with respect to obesity and hypertension have been limited so far. Thus, while conducting the “Hypertension and Diabetes Risk Screening and Awareness Study” in September 2001 [11], we gathered data on the prevalence of obesity and hypertension in primary care. These data are of particular value for the characterization of obesity-hypertension and may serve as the basis for future improvements in this field. Therefore in this article we report 1) blood pressure readings of patients in primary care according to age and BMI respectively, 2) the point prevalence of hypertension in obese patients based on the criteria adopted by NHANES, and 3) the proportion of treated controlled and uncontrolled hypertension in the sample population of obese primary care patients.


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METHODS Study design The design and instruments of HYDRA has been presented in greater detail elsewhere [11]. Briefly, HYDRA is based on a two-step epidemiological design. In step one, a nation-wide sample (n= 2,466) of primary care doctors completed a prestudy questionnaire (n=1,912; response rate: 79 %) to describe personal and structural characteristics of each practice and to assess self-perceived qualifications and attitudes related to recognition, diagnosis, and care of primary care patients. The 2nd step consisted of a target day assessment (half day September 18 or 20, 2001) of all patients attending the 1,912 doctors’ offices on this day. Patients were informed by posters and leaflets about participation of the respective practices in the study and that they were free to decline participation. Oral informed consent was obtained from all patients. They completed a self-report patient questionnaire, followed by a structured doctors’ clinical appraisal, including documentation of lab test findings from the charts, blood pressure measurements, and assessment of microalbuminuria and blood glucose in spot samples. Irrespective of their reason for contacting the primary care physician a total of n=45.125 consecutive primary care attendees, aged 16 and above and eligible for the study, were enrolled (response rate: 87 %; 18,065 males, 27,061 females). Typical for primary care settings, a large proportion of these patients was of older age (proportion aged 60 or above: 42.2 %).

Instruments: The prestudy questionnaire served to collect information on participanting physician’s profile (education and specialization), practice setting, and physician’s attitude and


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perceptions towards guidelines and programs for diabetes and hypertension management. The patient questionnaire was used to collect data on a variety of variables including biosocial characteristics, quality of life measures, life-style and behavioral risk factors, health status, and details on hypertension and diabetes history and treatment (if applicable). The doctor's clinical appraisal included rating of the current presence of hypertension and diabetes using the Clinical Global Impression Scale (CGI: not present, borderline, mild/moderate, severe/extreme) [12] and indicating comorbidities out of 22 predefined somatic and mental disorders. Information on blood pressure and clinical chemistry as well as the doctor’s assessment of diabetes and/or hypertension control was also collected. In addition, systolic and diastolic blood pressure was measured by indirect cuff sphygmomanometry after several minutes of rest in sitting position as recommended [13].

Diagnostic conventions In general, diagnostic findings reported rely on the doctor's clinical diagnoses as reported and coded in the clinical appraisal form. Diagnosis of hypertension was based on the definition adopted by NHANES [8] which defined hypertension as measured blood pressure equal to or greater than 140/90 mmHg and / or receiving antihypertensive therapy. Body weight and height information were taken from the patients questionnaire. The BMI was calculated from these self-report data (bodyweight in kg / height in meter squared) and classified according to international conventions [7, 14, 15] (Table 1).


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Statistical analyses Prevalence estimates have not been adjusted for drop outs that occurred either as the result of refusal to participate or because of exclusion of subjects because of incomplete reports. From the total HYDRA sample of 45,125 patients 6,252 dropped out due to missing values for weight and height, missing blood pressure readings and missing CGI ratings for diabetes and hypertension. Thus these point prevalence estimates are based on a sample of 38,873 primary care attendees. Cross tables, frequency distributions and descriptive statistics were used to compare the distributions of variables among all categories. All analyses were conducted using the Stata 7 software package (Stat Corp., USA 2001).


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RESULTS

Mean blood pressure readings Blood pressure readings in patients in primary care increase with age and higher body mass index (BMI). When dividing the patients into subgroups that are either untreated or treated for hypertension it becomes evident, that patients with treated hypertension still show higher readings, the mean of which is still in the hypertensive range (> 140 mmHg systolic, see figure 1).

Compared with controls, that show normal weight (mean blood pressure 126 / 78 mmHg) readings increase with increasing weight and mean blood pressure in grade 3 obese patients is highest with values of 142 / 84 mmHg. The blood pressure in patients with no treatment increases (+8/+4 mmHg) from normal to overweight body mass, in patients on treatment its only +1/+1 mmHg. Treated hypertensive patients with normal weight show an average blood pressure of 143 / 83 mmHg with a continuous rise up to 148 / 87 mmHg in treated hypertensive patients that are grade 3 obese. The more overweight / obese patients are the more they miss their recommended blood pressure goals.

Prevalence of hypertension (> 140 and/or > 90 mmHg) in overweight / obese patients The overall prevalence of hypertension is increasing with age in patients with normal weight as it does in patients with higher BMI classes (table 2). Primary care attendees with normal weight and young age have the lowest prevalence with 8.57 %. Grade 2 obese patients aged 60 – 74 have the highest prevalence with 89.20 %. But while the increase


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with age is most prominent in patients with normal weight (+ 67.66 % oldest vs. youngest age group) it is comparably small in patients with grade 2 obesity: 51.39 % of these patients are hypertensive already in the young (16-29 years), their older counterparts between over 74 years are hypertensive in 85.71 % (+ 34,32 %).

The prevalence of hypertension is generally higher in males than in females up to the age of 59. For example men aged 16-29 with normal weight have a prevalence of hypertension of 13.36 % while in women it is only 5.84 %. Grade 2 obese men have hypertension in 77.78 % of cases, women in only 35.56 %. But as soon as reaching the age of sixty prevalence of hypertension is often higher in women than in men. In patients beyond 75 the prevalence is consistently higher in all weight categories but one, namely the ones with grade 2 obesity, where men are hypertensive in 91.67 % and women in 84.31 % of cases.

Looking at patients between 45 and 59 it becomes clear that also the increase in body mass index is associated with an increase in hypertension prevalence. 37.16 % of these patients are hypertensive already in the subgroup with normal weight. But hypertension increases with increasing weight: 55.15 % of the patients that are overweight (OR=2.09; 95%CI=1.84-2.38), 73.29 % of the patients that are grade 1 obese (OR=4.53; 95%CI=3.635.66), 79.46 % of the patients that are grade 2 obese (OR=9.00; 95%CI=5.4314.92) and 79.57 % of the patients that are grade 3 obese (OR=5.02; 95%CI=2.82-9.58) are hypertensive. Generally the prevalence of obesity in the subgroup with the highest body mass index is slightly lower in the patients with grade 3 obesity, turning around the trend manifested in the less obese.


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Taken together the prevalence of hypertension is not only increasing with age and is higher in men than in women (at least in the younger age groups), but it is also steeply increasing in overweight and obese patients. Overall prevalence of hypertension in normal weight is 34.25 %, in overweight it is 60.84 %, grade 1 obesity 72.86 %, grade 2 obesity 77.12 %, and grade 3 obesity 74.14 %. It goes parallel with weight increase until grade 2 and is slightly under proportional in grade 3.

Prevalence of hypertension with a more stringent blood pressure target (> 130 and/or > 80 mmHg) in overweight / obese patients Taking more stringent blood pressure goals as applicable for patients with high cardiovascular risk as will be detailed on further down the situation is much worse. Starting with 67.83 % of the patients with normal body weight (for these the lower targets would not apply), prevalence of hypertension increases to 87.06 % for these overweight (OR=2.1, 95%CI=1.99-2.22), 92.1 % for grade 1 obese (OR=3.94, 95%CI=3.64-4.26), 95.04 % for grade 2 obese (OR=6.03, 95%CI=5.21-6.98) and 91.72 % for grade 3 obese patients (OR=5.52, 95%CI=4.43-6.88).

Hypertension diagnosis, treatment and control In male patients with normal weight 60 % (66 % female) of actually hypertensive patients are diagnosed as such, 51 % (58 % female) are on treatment and only 18 % (20 % female) are controlled (< 140 and < 90 mmHg). With increasing weight (BMI) the proportion of diagnosed patients is increasing (84 % in patients with a BMI > 40) (86 % in female) as


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does the number of treated patients (73 % in male, 75 % in female). Thus the gap between diagnosed and consequently treated patients is similar throughout all BMI classes (roughly 10 %). But the proportion of patients that are controlled is constant with 18 % of patients that are controlled (20 % female). It even declines in patients up to grade 2 obesity, but improves in grade 3 obese (22 % of men and 20 % of women are controlled). Therefore the discrepancy between patients that are “diagnosed and treated” and the ones that are controlled increases with higher BMI classes and is highest in patients with grade 2 obesity. (Bramlage: Still need actual figures from Mr. Höfler)


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DISCUSSION In this paper we demonstrated that the prevalence of hypertension in overweight and obese patients in primary care is high and is steeply increasing with the grade of obesity. Overall prevalence of hypertension in normal weight is 34.25 %, in overweight it is 60.84 %, grade 1 obesity 72.86 %, grade 2 obesity 77.12 %, and grade 3 obesity 74.14 %. But although hypertension is more frequently detected in overweight patients, the discrepancy between the number of treated and the number of controlled patients is also increasing with increasing weight. Taking into account more stringent blood pressure goals, that are not yet established but would consider the increased cardiovascular risk of these patients, the prevalence of hypertension considerably increases with weight, being as high as between 91.72 and 95.02 % in obese patients.

Increasing blood pressure and increasing body weight (BMI) We were able to demonstrate the substantial increase in blood pressure not only with increasing age, but also with increasing body mass. Furthermore, blood pressure readings in patients that are treated for hypertension are still considerably higher than in patients without treatment. A large proportion of patients still misses the blood pressure goal of 140/90 mmHg. Doll et al. recently showed that both systolic and diastolic blood pressure increase in a linear manner over the whole range of body mass (BMI) or waist circumference [16]. In regression models corrected for the age-related rise in blood pressure, a gain of 1.7 kg/m2 for men or 1.25 kg/m2 for women in BMI is associated with an increase in systolic blood pressure of 1 mm Hg [17]. (Bramlage: still needs some discussion)


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Prevalence of Hypertension. Hypertension is a pivotal risk factor of cardiovascular complications in obese patients. These complications comprise coronary heart disease, stroke, or renal insufficiency and lead to an increased morbidity and mortality. The Third National Health and Nutrition Examination Survey (NHANES III), which was conducted from 1988 to 1994 reported an increasing rate of hypertension with increasing BMI class [6]. While the prevalence of Hypertension (> 140 and / or > 90 mmHg) was 23.47 % for men with normal weight (23.26 % for women) it was 34.16 % (38.77 %) for overweight, 48.95% (47.95 %) for class 1 obesity, 65.48 % (54.51 %) for class 2 obesity and 64.53 % (63.16 %) for class 3 obesity. The steep increase in prevalence is in good agreement with the one reported in this study, though the profile is somewhat different in that the prevalence of hypertension is considerably higher throughout all BMI classes. This may be attributable to the fact, that the population that has been under investigation in this study is different in NHANES III (general population based study) and in HYDRA (primary care attendees).

Optimal Blood Pressure Levels in Obese Patients Current guidelines define blood pressure values below 120/80 mmHg as optimal, values below 130/85 mmHg as normal, values between 130/85 to 139/89 mmHg as high normal, and values greater than 140/90 mmHg as hypertensive [8, 9]. For obesityhypertension there are no specific recommendations. An estimate based on the metabolic context of obesity and its cardiovascular complications would suggest blood pressure goals for obesity-hypertension similar to the ones of patients with type-2-diabetes: Type-2-diabetes is tightly correlated with body


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weight and age [18, 19]. Young patients that are obese and who already have developed manifest arterial hypertension are extremely likely to be insulin resistant and, in turn, are at high risk of developing type-2 diabetes [20]. In addition, higher age is associated with type2 diabetes [19]. For type-2 diabetics, it has been shown that tight blood pressure control is one of the most important treatment strategies that should be initiated early. It would therefore make sense to treat obese hypertensive patients in a similar way as hypertensive type-2-diabetics.

Lack of diagnosis, treatment and control Most patients with obesity-hypertension are classified as having a high or very high cardiovascular risk [8, 9]. Therefore these patients should be given special attention and special recommendations are warranted for the treatment of obesity-hypertension. But though treatment of these patients has been documented to be a particular challenge, recent guidelines for the treatment of hypertension (WHO / ISH, JNC) have not recommended special approaches for overweight patients besides the rather general recommendation to lose weight [8, 9]. Previous analyses of the HYDRA study have been showing, that the gap between the number of people on treatment and the ones that are finally controlled is substantial [11]. These findings of 18.7% of controlled hypertension in primary care are also in the same magnitude to the 23 % of hypertensive patients with controlled hypertension reported in NHANES III for the United States using the same cut off [21]. Taking into account differences in the sample composition the findings appear to be also similar to the rates for diagnosis and control reported in the Framingham 4-years follow up


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of untreated hypertensive patients, revealing control rates of 31% to less than 140/90 mmHg [22]. Classifying the primary care attendees according to weight as has been done in this study makes evident, that increasing weight adds considerably to this in that the number of treated but uncontrolled patients outnumber the ones that are finally controlled by far. Probability of insufficient control of blood pressure in obese patients is 50 % higher than in hypertensive patients with normal weight (BMI 18.5 – 24.9 kg/m2) [10].

Potential limitations Blood pressure readings have been obtained only once on the study day after three minutes of rest. Therefore one might argue that not all patients that had a blood pressure reading in the hypertensive range ( > 140 and / or > 90 mmHg) may have actually been hypertensive patients. While this may hold true when looking at single individuals for which the predictive value of a one time test may be limited, it has been shown that one time blood pressure testing is feasible and gives reliable estimates for large cohorts of patients [23].

Conclusion This study documents the high prevalence of hypertension in overweight and obese patients and the striking lack of control as compared to hypertensive patients with normal weight. Consequently the likeliness for these patients to develop cardiovascular morbidity and subsequent mortality is greatly enhanced. Obviously control is particularly difficult in


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obese patients. This calls for evidence based recommendations for the treatment for obesity-hypertension.

Acknowledgments This study was supported by an unrestricted educational grant by SanofiSynthelabo, Germany. We acknowledge the commitment of the participating physicians and their staff, without whom the present study would not have been possible.


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Hu, F.B., et al., Diet, lifestyle, and the risk of type 2 diabetes mellitus in women. N Engl J Med, 2001. 345(11): p. 790-7.

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Cowie, C.C. and M.I. Harris, Physical and metabolic characteristics of persons with diabetes., ed. N.I.o.D.a.D.a.K.D. National Diabetes Data Group. Bethesda: National Institutes of Health. 1995. 117-164.

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Table 1: BMI categories underweight

< 18.5 kg/m2

normal weight

18.5 – 24.9 kg/m2

overweight

25 – 29.9 kg/m2

obesity obesity grade 1 obesity grade 2 obesity grade 3

>= 30 kg/ m2 30 – 34.9 kg/m2 35 – 39.9 kg/m2 > 40 kg/m2


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Figure 1: Blood pressure readings are increasing with age and higher BMI


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Figure 2a: Diagnosis, Treatment and Control in Hypertensive Men Diagnosis, Treament and Control in Hypertensive Men

Percent

0 10 20 30 40 50 60 70 80 90 100

by BMI (kg/m2)

18.5-24.9

25.0-29.9

30.0-34.9

diagnosed diagnosed + treated + controlled

35.0-39.9

40+

diagnosed + treated

Figure 2b: Diagnosis, Treatment and Control in Hypertensive Women Diagnosis, Treament and Control in Hypertensive Women

Percent

0 10 20 30 40 50 60 70 80 90 100

by BMI (kg/m2)

18.5-24.9

25.0-29.9

30.0-34.9

diagnosed diagnosed + treated + controlled

35.0-39.9

40+

diagnosed + treated

Figure Legend: Hypertension is either BP > 140 and or 90 mmHg or on antihypertensive medication


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