1 Department of Hygiene and Epidemiology, School of Medicine, University of Athens, Greece
2 Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA
3 Department of Ichthyology and Fisheries, Technological Educational Institute of Epirus, Igoumenitsa, Greece
Correspondence: Dimitrios Trichopoulos, Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA. E-mail: dtrichop{at}hsph.harvard.edu
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Abstract |
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Methods In the context of the Greek component of the European Prospective Investigation into Cancer and nutrition (EPIC), 26 913 volunteers, aged 2086 years, were recruited from several regions of Greece. Blood pressure measurements were taken by trained physicians and standard interviewing procedures were used to record medical history, and socio-demographic and lifestyle characteristics. The data were modelled through multiple regression.
Results The prevalence of hypertension (based on two arterial blood pressure measurements on a single occasion) is 40.2% for men and 38.9% for women (age-adjusted to the adult Greek population of 2001). In the sample examined, awareness among hypertensives is 54.4%, pharmaceutical treatment among those aware is 83.9%, and effective control among hypertensives is 15.2%. Prevalence of hypertension increases with age and is higher in rural areas and among individuals of lower education. Awareness and control of hypertension is higher among older individuals, among women and among the highly educated. Moreover, awareness of hypertension is higher among rural residents, whereas control of hypertension is more effective among urban residents.
Conclusions In a large sample of the general Greek population, the prevalence of hypertension among men is lower than the average among the EU countries, whereas the corresponding prevalence among women is higher. Awareness and control of hypertension is lower in Greece than in other western countries, making them public health priorities.
Accepted 10 May 2004
Premature mortality from cardiovascular diseases could be prevented, to a considerable extent, by the effective control of hypertension, a major risk factor for this group of diseases.1 Hypertension is the third killer, according to the World Health Organization, accounting for one in every eight deaths worldwide.2 It increases the risk of stroke, myocardial infarction, congestive heart failure, sudden cardiac death, peripheral vascular disease, and renal insufficiency.36
Results from the Seven Countries study have suggested that the relative increase in mortality from coronary heart disease for a certain increase of blood pressure is similar among different populations. When comparing absolute risks of death at the same level of blood pressure, however, rates varied substantially, with rates in the US and northern Europe being higher in comparison with rates in Mediterranean southern Europe and Japan.7,8
Apart from the Seven Countries study, which has used samples from two islands in Greece, data for hypertension in Greece have been presented in the ATHENS study (sample from Athens),9 the Didima study (sample from a rural area),10 and the ATTICA study (sample from the province in which the capital of the country is located).11 Nationwide data for the status of hypertension in the adult population of Greece are not available. The purpose of this study was to provide data for Greece overall, concerning the prevalence, awareness, treatment, and control of hypertension. The relationship of hypertension with level of education and type of residence was also examined.
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Materials and methods |
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For this study, hypertension was defined as SBP 140 mmHg, or DBP
90 mmHg, or previous diagnosis of hypertension, or current use of antihypertensive medication or any combination of the above. Definition of hypertension in this study includes two, on a single occasion, ascertainments of blood pressure. Awareness of hypertension was defined as a subject's report of a previous medical diagnosis of hypertension. Treatment of hypertension was defined as current use of a prescribed medication intended to lower blood pressure. Study participants with evidence of hypertension were asked whether they are using pharmaceutical treatment for hypertension (not including dietary supplements or lay medicines). Control of hypertension was defined as SBP <140 mmHg and DBP <90 mmHg. Control could be achieved by either pharmaceutical or non-pharmaceutical means.
Educational attainment was determined through years of schooling. For the purpose of this analysis, each subject was classified into one of three categories: elementary educational level included people who were no more than graduates of primary school (6 years of education); secondary educational level included attendees or graduates of secondary and technical school (>6 years but
14 years of education); higher educational level included university attendees or graduates (>14 years of education). Type of residence was determined according to the size of the area where the subject resided. Urban areas were those having >10 000 inhabitants, whereas rural (including semi-urban) areas were those with
9999 inhabitants.17
For the analysis, study subjects were classified by gender, age, any evidence of hypertension as previously defined, awareness of their condition, pharmaceutical treatment for it and effectiveness of treatment. Subsequently, odds ratios (OR) contrasting the indicated groups (those with evidence of hypertension versus no evidence; among hypertensives, those with awareness of hypertension versus no awareness; among those aware, those with drug treatment versus no treatment; among those receiving pharmaceutical treatment, those with effective versus ineffective treatment; and among hypertensives, those with effective control versus no control) by gender, age, type of residence, and educational level were estimated by modelling the data through multiple logistic regression. The STATA package was used.18
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Results |
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Discussion |
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Hypertension is a universal problem and is an important risk factor for stroke, the mortality from which is considerably higher in Greece than the European Union countries average, particularly with respect to women.20 Our findings provide a possible explanation of the problem, since in our study the prevalence of hypertension is as high among women as among men in contrast to what is found among other European Union countries in which the prevalence of hypertension is generally higher among men than among women.21 Greek women are more obese than all other nationals in the European EPIC study, providing an indication of the likely root of the problem.2224 The underlying role of obesity is reflected in the difference in hypertension prevalence between people educated 6 years in comparison with those educated for
15 years. Among the least educated, the prevalence of hypertension is more than twice that among the most educated and the contrast is more striking among women than among men (Table 2). Similarly, the least educated have higher body mass index compared with the most educated and the contrast is more striking among women than among men (mean values, among men 28.6 versus 27.4; among women 30.5 versus 25.8) (crude comparisons, unpublished data).
Comparisons of prevalence of hypertension among population groups in different countries is hindered by the fact that in various studies variable operation definitions and methodologies are used for the ascertainment of hypertension and age- and gender-adjustment is not uniformly done. Age- and gender-adjustment depends on both sample composition and adjustment to the standard population chosen, but the demographic similarity of most North American and European Union populations makes the second issue less critical. Overall, it appears that the prevalence of hypertension among Greek men is not higher than the European average, whereas the prevalence of the condition among Greek women is at a comparatively higher level.2530 It is also of interest that the prevalence of hypertension and mortality from stroke are both lower in the US and Canada than they are in Greece; in Greece, the problem is also compounded by the lower levels of awareness and effective control of the condition, in comparison with other developed countries.3133
In contrast to prevalence of hypertension that has both biological and lifestyle components, awareness and effective control of the condition strongly depend on aspects of the health care system. Although medical doctors in Greece tend to be concentrated in urban areas, their very large number (approaching 60 000 in a population of slightly over 10 million) allows adequate staffing of community clinics, which are available in virtually all rural areas. Antihypertensive medication is provided at minimal charge in both urban and rural areas. In rural areas, community clinics are staffed by young doctors, who do a mandatory one-year service and they are likely to be less experienced in the proper management of hypertension, but quite liberal in subscribing mild antihypertensive regimens. Both awareness and effective control are lower in the Greek population than in populations of more developed western countries,2533 which points the way towards a need for prevention of the hypertension-related stroke mortality that is particularly high in Greece. The results of our study (Table 4) are compatible with earlier observations in indicating that control of SBP may be more difficult that control of DBP.34 Detection of hypertension is the necessary first step towards control of this condition at the population level, and the findings of our study (last column in Table 5) indicate that resistance to effective control is higher among younger men, of limited education, particularly in rural areas. These results of course are culture-specific, but they are compatible with those reported from other countries.25
Advantages of the present study are the large sample study, its general population coverage, its nationwide scope, and its reliance on a standardized protocol. The study is considerably larger than earlier investigations in Greece that have targeted population groups in specific towns or geographical areas.911
Our sample was not strictly representative, since for ethical and practical reasons it had to rely on volunteers. Achieving the necessarily very high response fraction for a nationwide representative population sample for procedures that involve clinical examinations is next to impossible, at least for the Greek population. Identifiable selection factors, however, including age, gender, education, and residence were adjusted for in the multivariate analysis, so that the validity of the results concerning the impact of these factors on prevalence, awareness, treatment, and control of hypertension is preserved. Prevalence of hypertension may have been overestimated35 and effective control of the condition underestimated because the two blood pressure measurements were performed on one occasion only. This, however, should have minimal effects on the results concerning the within the sample comparison and it is an inherent problem of large size epidemiological investigations.36 Information bias may have been present with respect to both recall of hypertension diagnosis and treatment and the validity of some of the predictor variables (example given educational level), but we consider the extent of such biases and the possible impact on the results minimal, given the confidential nature and the health objectives of the EPIC investigation. Moreover, exclusion from the analysis of individuals who had a previous diagnosis of hypertension, but are currently normotensives without treatment, could have created a more extensive bias in the study base. Misclassification of blood pressure measurements is unavoidable, notwithstanding the quality control processes that were in place throughout the study. The effects of non-differential misclassification should be minimal with respect to prevalence estimation, but are likely to have led to some attenuation of the effect measurements (regression coefficients). Since the mid 1990s, the prevailing view in the medical community in Greece was that hypertension could be defined on the basis of the cut-offs of 140/90 mmHg, so that there has been no secular change in the operational definition of the condition.
In conclusion, in a large countrywide general population in Greece we have documented that the prevalence of hypertension among men is lower than the average among the European Union countries, whereas the corresponding prevalence among women is higher. This pattern is reflected in the high mortality from stroke among women in Greece. Awareness and control of hypertension is lower in Greece than in highly developed western countries, making prevention of hypertension a public health priority in this country. On the basis of findings concerning sociodemographic predictors of effectiveness of hypertension control it is evident that hypertension efforts should be concentrated among the less-educated population groups.
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Acknowledgments |
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References |
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