Abstract
Introduction. Cardiovascular disease (CVD) is a major cause of mortality, and has risk factors, which can be treated by lifestyle changes or medications. Abdominal obesity has been identified as the second strongest risk factor for myocardial infarction. Objectives. To assess the frequency of abdominal obesity and its relationship with hypertension (HT) and CVD in patients in Poland, and to compare frequencies of adiposity, HT and CVD between Poland and the North-West Europe Region, obtained in the IDEA study. Methods. In Poland, general practitioners included 5371 patients, aged 18–80 years, eligible for analysis. Waist circumference (WC) was measured, and the presence of HT and CVD recorded. Results. Increasing WC was significantly associated with HT and CVD, after adjustment for age (p<0.001). The frequency of abdominal obesity (WC >102/88 cm) was higher in Poland than in North-West Europe (36% vs 33% in men and 54% vs 45% in women, respectively, p<0.0001). Similarly, the frequency of HT in Poland was higher than in North-West Europe (47 vs 36% in men and 45 vs 30% in women, respectively p<0.001). In Poland CVD was 1.7-fold more frequent in men and 2.5-fold more frequent in women, compared with North-West Europe. Conclusion. In Polish adiposity, both WC and body mass index (BMI) were strongly related to HT and CVD. The frequency of abdominal obesity, obesity, HT and CVD in primary care patients is substantially higher in Poland than in North-West Europe.
Introduction
Cardiovascular disease (CVD) is a major cause of morbidity and mortality in the contemporary world (Citation1). Therefore, the identification of potentially modifiable risk factors for CVD is of great importance. The metabolic syndrome, a cluster of potentially modifiable risk factors, is becoming more prevalent around the world, reaching the level of nearly 50% in the older age groups (Citation2–5). Obesity and, in particular, abdominal obesity, is a growing clinical and public health problem, which has been consistently associated with hypertension (HT), type 2 diabetes (Citation6–8) and CVD (Citation9). In the INTERHEART study, abdominal obesity was the second strongest risk factor for myocardial infarction (Citation10,Citation11).
There are substantial regional differences in the frequency of abdominal obesity, ranging from 8% among men in Greenland to 65% among women in Spain (Citation12). The level of abdominal obesity in the United States reaches very high values in the general population with a continuous increase over the last decades (Citation13). Waist circumference (WC) measurement is a practical way to assess abdominal obesity in everyday practice (Citation14,Citation15). However, until recently, little was known about the worldwide frequency of abdominal obesity in primary care.
The IDEA study was the first global survey in primary care and it aimed to evaluate the level of obesity and abdominal obesity (Citation16,Citation17). This report presents data of Polish participants in the IDEA study: the frequency of adiposity and its relationship with and CVD in patients attending primary care physicians. These findings were compared with those obtained in the IDEA study from the North-West Europe Region (Austria, Belgium, Denmark, Finland, France, Germany, Ireland, The Netherlands, Norway, Sweden, Switzerland).
Methods and materials
Design
The International Day for Evaluation of Abdominal Obesity (IDEA) study was an international, non- interventional, cross-sectional study, designed to collect worldwide data on abdominal obesity in patients visiting primary care physicians. The detailed study design and methods were previously described (Citation17).
The Idea Poland study was designed and performed following the same procedures and protocol as the International IDEA study, which recruited primary care physicians randomly, to obtain a representative sample with a balance of rural and non-rural practices.
Participants
A total of 5916 patients aged between 18 and 80 consulting their primary care physicians on the two pre-specified half days were asked for informed consent and invited to participate in the study, irrespective of their reason for consultation. They gave written informed consent. Women with known pregnancies were excluded.
Before the IDEA days, the physicians underwent a short course on the IDEA project – the procedure to recruit patients, collect data and measure WC. Each physician was asked to record age, gender, height, weight and WC (measured midway between the lowest rib and the iliac crest – consistent with the World Heart Foundation recommendations) of all recruited patients. Furthermore, they collected data regarding the presence of reported CVD (defined on the form as coronary heart disease, stroke or revascularization), diabetes (type 1 or 2), HT or dyslipidemia. The study was non-interventional and performed according to good clinical practice. All patients provided written, informed consent.
Sample size
The number of patients included in the IDEA study ranged between 1100 and 9600 per country, in order to estimate obesity frequency with a precision of 1–3%. In Poland, the sample size was defined at 5900.
Randomization of primary care physician centers
All centers participated in the IDEA study have been randomly selected in order to have a good representation of the sample of physicians in each country. In Poland, 599 general practitioners were contacted by Cedegim, a clinical research organization; 200 physicians agreed to participate in the study.
On-site quality assurance procedures were conducted by qualified personnel, for random selections of 10 patients attending 5% of the study sites. Quality control procedures were completed within 5 days following the data form collection from the selected study sites.
Statistical analysis
Patient characteristics are presented as frequencies, means with SD, medians with quartiles and min, max. Obesity was defined as a body mass index (BMI) ≥30 kg/m2 and overweight BMI between 25 and 30 kg/m2. Abdominal obesity was defined according to the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATPIII) recommendations (WC>102 cm in men and >88 cm in women) (Citation3), and the International Diabetes Federation (IDF) criteria (WC≥94 cm in men and ≥80 cm in women) (Citation4). Age-adjusted odds ratios (ORs) for HT and CVD were calculated for 1SD increase in WC and BMI, separately for men and women, using logistic regression with age as a continuous variable. The frequency of known HT and CVD for men and women, adjusted for age and smoking status, by gender-specific WC tertiles, and BMI categories were calculated using logistic regression with age as a continuous variable. For comparison between Polish data and findings from the North-West Europe, proportions were analyzed using χ2 tests. Calculations used Stata software v. 10.0 (Stata Statistical Software: Release 10, Stata Corporation, College Station, TX).
Results
Study participants
In Poland, a total of 5916 patients were screened for entry into the study; 5371 patients (91%) fulfilled the entry criteria, and had no missing or invalid data. The mean age of participants was 50±16 years. The study included 2024 men and 3347 women from all geographic areas of the country. Characteristics of the patients (WC, obesity, CVD, HT, lipid disorders and smoking status) in males and in females are presented in .
Table I. Characteristics of patients in Poland.
Distribution of WC
Mean WC was 91 cm in women and 99 cm in men. Overall 38% of men and 54% of women had abdominal obesity using the NCEP-ATP III criteria (Citation3). Using the IDF Caucasian criteria (WC≥94/80 cm for men/women) (Citation4), the frequency of abdominal obesity increased to 65% in men and to 74% in women.
Obesity status according to BMI
We found that men in Poland were more frequently overweight (BMI 25–30 kg/m2) compared with women, respectively 41% vs 33% (p<0.001), whereas we did not find a difference in obesity (BMI≥ 30 kg/m2) between men and women (both 33%).
HT and CVD: impact of WC and body mass index
The frequency of known HT was 47% in men and 45% in women and CVD was more common in men (32%) than in women (28%) (p<0.001).
Increasing WC and BMI were independently and significantly associated with HT and CVD, as shown in . The WC and BMI were more strongly correlated with HT than with CVD, for both men and women ().
Table II. Age-adjusted odds ratios (ORs) and 95% confidence intervals (CI) for hypertension and cardiovascular disease (CVD) associated with a 1SD increase in waist cirumference (WC) or body mass index (BMI) in Poland.
The frequency of CVD and known HT, adjusted for age and smoking status, increased with WC within each BMI category and with BMI in each WC tertile ( and ), for both men and women. Moreover, both HT and CVD were associated with WC, even in non-obese patients with BMI below 25 kg/m2.
Figure 1. Synergistic effect of waist circumference and body mass index (BMI) on the frequency of hypertension in men (A) and women (B). The results are adjusted for age and smoking status.
Figure 2. Synergistic effect of waist circumference and body mass index (BMI) on the frequency of cardiovascular disease (CVD) in men (A) and women (B). The results are adjusted for age and smoking status.
The results showed that WC and BMI were more strongly associated with HT, than with CVD. This observation was confirmed also among non-obese patients (i.e. with BMI<25 kg/m2) in both sexes ( and , or and ).
Relationship between abdominal obesity and reported HT and CVD
The analysis of the association between abdominal obesity, measured by WC according to the NCEP/IDF criteria, and the frequency of HT and CVD, showed its strong influence on the frequency of both conditions. The age-adjusted ORs for HT and CVD according to the NCEP/IDF criteria of abdominal obesity are shown in .
Figure 3. The age-adjusted odds ratios (ORs) for hypertension (A) and cardiovascular disease (CVD) (B) according to the National Cholesterol Education Program (NCEP)/International Diabetes Federation (IDF) criteria of abdominal obesity.
Comparing patients from the lowest and the highest tertiles of WC showed more than threefold increase in HT frequency and over a twofold increase in CVD frequency.
Impact of smoking status
Smoking was associated with lower WC in women (p<0.001), but not in men (p >0.1). Statistical analysis with and without adjustment for smoking status revealed very similar odds ratios in both models, indicating that the relationship between abdominal obesity and cardiovascular risk is independent of smoking status.
Frequency of abdominal obesity, HT and CVD in Poland in comparison with North-West Europe
The mean patient age was similar in Poland and in North-West Europe (52 years for both locations). Significant differences in the frequencies of obesity, abdominal obesity, HT and CVD in primary care patients in Poland and North-West Europe were found.
The frequency of obesity was higher in Poland than in the North-West Europe Region (33% vs 23% among both men and women; p<0.001 for both). Abdominal obesity, defined according to the NCEP classification, was also higher in Poland than in North-West Europe. This difference was more striking for women (54% in Poland vs 45% in North-West Europe, p<0.001) than for men (38% vs 33%, respectively; p<0.01). Similarly, the frequency of recorded HT in Poland was higher than that in North-West Europe (47% vs 36% for men and 45% vs 30% for women, respectively: p<0.001 for both). Finally, CVD in Poland was 1.7-fold more frequent in men and 2.5-fold more frequent in women than in their counterparts from North-West Europe. The frequency of reported CVD in Poland and North-West Europe was 32% vs 19% for men and 28% vs 11% for women (p<0.001 for both) ().
Table III. Prevalence (%) of obesity, abdominal obesity using the NECP classification, known hypertension and cardiovascular disease (CVD) in Poland and North-West Europe.
Discussion
The present study provides the first data on the frequency of abdominal obesity, adiposity and associated risk factors in patients attending primary care physicians in Poland. Similarly to other countries, both obesity and abdominal obesity are strongly related with HT and CVD. However, the frequencies of obesity, abdominal obesity, HT and CVD are substantially higher in Poland than in North-West Europe. It is particularly striking that CVD among patients attending primary care physicians in Poland is 1.7-fold more frequent in men and 2.5-fold more frequent in women compared with their counterparts from North-West Europe.
Relationship between abdominal obesity and HT and CVD
WC could be the simplest method for measuring the abdominal obesity since a close correlation was found between WC and the amount of intra-abdominal fat found on computed tomography (Citation18).
WC and BMI were strongly associated with HT and CVD. Moreover, both HT and CVD were associated with WC, even in non-obese patients with BMI below 25 kg/m2. This indicates a high likelihood of under diagnosis of individuals at risk, unless WC is measured in parallel with BMI, provided the reference values for WC are good predictors of metabolic risk (Citation19).
These observations are consistent with the overall results of the IDEA study, indicating that the negative effect of overall fat excess is increased in cases where abdominal adipose tissue is increased (Citation20). The presence of abdominal or visceral fat signifies an increase in metabolic activity, an increase in unfavorable inflammatory markers, and a higher insulin resistance, leading to perturbation of glucose homeostasis (Citation21–24).
Abdominal obesity, expressed as waist-to-hip ratio, was shown to be associated with the risk of CVD (myocardial infarction namely) in the INTERHEART study. After smoking, abdominal obesity was the strongest risk factor for the development of myocardial infarction (Citation10,Citation11).
Comparison with previous studies in Poland
Comparing the results of the IDEA study with the NATPOL PLUS study carried out in 2002, on a representative sample of Polish citizens, the frequency of abdominal obesity, defined according to the NCEP criteria, was higher in the IDEA population (37% in men and 54% in woman) than in NATPOL PLUS survey (20% in men and 37% in women) (Citation25,Citation26).
Similarly, overweight and obesity (according to the level of BMI) were more frequent in the IDEA study (74% in men and 66% in women) than in NATPOL survey (58% men, 48% woman) (Citation5). HT was less prevalent in NATPOL survey than in the IDEA study (29% vs 46%), with no major differences between genders in these studies.
There are several factors that might explain differences between the two studies. First, participants in the IDEA study were primary care patients, whereas the NATPOL study was carried out on a nationally representative sample of adult Polish citizens (n = 3051). Participants in the IDEA study were consulting a primary care physician (for any reason), whereas in NATPOL study the sample was randomly selected to assure that it was representative of the general Polish population.
Second, participants in the IDEA study were older than NATPOL participants (52±16 vs 46±17 years). Thus, inclusion criteria and characteristics of the enrollment strategy might explain the higher frequency of concomitant diseases (such as hypertenion, diabetes or hyperlipidemia) in the IDEA study. Last but not least, the NATPOL study was performed in 2002, and perhaps the high frequency of obesity in the recently completed IDEA study reflects body weight changes in the population, as observed in other populations around the world, now reaching epidemic range in some of them (Citation27).
Comparison with the North-West Europe
Obesity, abdominal obesity, HT and CVD were more frequent in Poland than in North-West Europe. Abdominal obesity and BMI were strongly associated with HT, indicating that obesity may contribute to the elevated levels of blood pressure in a large proportion of Polish hypertensive patients. A high frequency of obesity-related HT might, at least partially, explain increased rates of CVD in the Polish population compared with North-West Europeans.
It is likely that non-hemodynamic factors associated with obesity may also contribute to CVD burden in Poland.
Limitations of the study
The primary limitation of this study is that the population included in IDEA is not representative of the general Polish population. The IDEA study included patients who consulted their primary care physicians on the IDEA days. Thus, results from the study cannot be extrapolated to the general population of the country. Secondly, the diagnosis of diseases (such as HT or CVD) were taken from primary care doctors’ reports, as this was a non-interventional study, and no diagnostic procedures were carried out. On the other hand, doctors’ reports are more trustworthy than patient reports, on which several other studies have been based. Thirdly, IDEA Poland and International study databases lack precise data regarding antihypertensive medication, which influence the body weight and adipose tissue distribution.
Important strengths of the IDEA study include the method of WC measurement, the training of all primary care physicians in the measurement of abdominal obesity, weight and height and the common worldwide management and analysis of the data.
In conclusion, our findings indicate that abdominal obesity, HT and CVD in primary care patients occur more frequently in Poland than in North- West Europe. The high frequency of abdominal obesity and HT in primary care physician setting might contribute to an increased burden from CVD in Poland, and require novel preventive strategies focusing on these risk factors.
Acknowledgements
The authors wish to extend their gratitude to the physicians and the subjects in Poland for their participation and contribution to the study. The interpretation of data and the decision to submit the manuscript was made by K. Narkiewicz, IDEA National Co-ordinator in Poland, independently of the funding source. The authors would also like to thank Ewa Kraszewska, Statmed Poland and Sandrine Brette, Statistician, Lincoln, France for statistical support. We thank Dr Balkau and Dr Després for editorial comments.
Data analysis/interpretation, concept/design, critical revision of article: M. Chrostowska, K. Narkiewicz and P. Paczwa. Approval of article: K. Narkiewicz. Drafting of article: M. Chrostowska, P. Paczwa and A. Szyndler. All authors had access to study data that supported the publication.
Funding: The IDEA study was funded by an educational grant from Sanofi-Aventis.
Conflict of interest: Dr Narkiewicz has received grant funding and honoraria from Sanofi-Aventis, Abbott and Roche. Dr Chrostowska has received grant funding and honoraria from Sanofi-Aventis and Abbott. Dr Szyndler does not have any conflict of interests. Dr Paczwa is an employee of Sanofi-Aventis.
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