Prevalence, awareness, treatment and control of hypertension in a Canarian population. Relationship with glucose tolerance categories. The Guía Study

North African influences and potential bias in case-control association studies in the Spanish population

Background

Despite the limited genetic heterogeneity of Spanish populations, substantial evidences support that historical African influences have not affected them uniformly. Accounting for such population differences might be essential to reduce spurious results in association studies of genetic factors with disease. Using ancestry informative markers (AIMs), we aimed to measure the African influences in Spanish populations and to explore whether these might introduce statistical bias in population-based association studies.

Methodology/Principal Findings

We genotyped 93 AIMs in Spanish (from the Canary Islands and the Iberian Peninsula) and Northwest Africans, and conducted population and individual-based clustering analyses along with reference data from the HapMap, HGDP-CEPH, and other sources. We found significant differences for the Northwest African influence among Spanish populations from as low as ≈5% in Spanish from the Iberian Peninsula to as much as ≈17% in Canary Islanders, whereas the sub-Saharan African influence was negligible. Strikingly, the Northwest African ancestry showed a wide inter-individual variation in Canary Islanders ranging from 0% to 96%, reflecting the violent way the Islands were conquered and colonized by the Spanish in the XV century. As a consequence, a comparison of allele frequencies between Spanish samples from the Iberian Peninsula and the Canary Islands evidenced an excess of markers with significant differences. However, the inflation of p-values for the differences was adequately controlled by correcting for genetic ancestry estimates derived from a reduced number of AIMs.

Conclusions/Significance

Although the African influences estimated might be biased due to marker ascertainment, these results confirm that Northwest African genetic footprints are recognizable nowadays in the Spanish populations, particularly in Canary Islanders, and that the uneven African influences existing in these populations might increase the risk for false positives in association studies. Adjusting for population stratification assessed with a few dozen AIMs would be sufficient to control this effect.

Blood pressure, antihypertensive treatment and factors associated with good blood pressure control in hypertensive diabetics: the Tarmidas study

Numerous population studies confirm the high prevalence of hypertension in type II diabetic (DM2) subjects and that intensive antihypertensive treatment is more beneficial to diabetic than to nondiabetic hypertensive subjects, yet not many of these are specific to Spain. To assess the degree of blood pressure (BP) control and the effects of antihypertensive drugs in the medical management of hypertension in diabetic patients in specialist care centres throughout Spain, we studied the socio-demographic, clinical and relevant laboratory parameters of 796 hypertensive patients with DM2 (mean age 66.09 (95% confidence interval (CI): 64.08-68.10). The percentage of diabetic patients responding positively to BP control measures was lower when compared to the nondiabetic population in both Spain and Europe. The degree of control was poorer for systolic than for diastolic BP, yet 40.6% of the patients were only on monotherapy. The fact that antihypertensive treatment was modified in only 40% of the poorly controlled patients was also highly significant and could be attributed to a nonstringent use of clinical guidelines. Among the other differences between well-controlled and poorly controlled patients, we found that well-controlled patients presented with lower levels of cholesterol and triglycerides, a lower prevalence of excess weight/obesity, and a greater prevalence of cardiovascular and/or cerebrovascular disease despite having a greater percentage of patients on antiplatelet therapy. Better application of therapeutic guidelines and the prevention and treatment of compounding factors could improve the response rate to BP control measures in poorly controlled patients.

Treatment and blood pressure control in 47,964 people with diabetes and hypertension: a systematic review of observational studies

BACKGROUND

Many patients with diabetes also have hypertension, greatly increasing their risk for cardiovascular disease. It has been suggested that hypertension is poorly treated in those with diabetes.

OBJECTIVE

To examine treatment and control of hypertension in people with diabetes.

DATA SOURCES

Data sources included MEDLINE, EMBASE, HealthSTAR, CINAHL, Web of Science, clinical evidence and government health and statistical Web sites.

METHOD

Databases were systematically reviewed and hand searches of the bibliographies of relevant studies (1990 to 2004) were conducted. Two investigators selected studies and extracted the data independently.

RESULTS

A total of 44 studies (77,649 subjects with diabetes, 47,964 [62%] of whom also had hypertension) were included. While 83% (range 32% to 100%) of patients with hypertension received drug therapy, only 12% (range 6% to 30%) had their blood pressure (BP) controlled to 130/85 mmHg or less. While BP control rates differed by definition of control (those studies with the least stringent definitions for BP control--160/90 mmHg or less--reported mean control rates of 37%), treatment and control rates did not differ appreciably between countries or health care settings.

CONCLUSIONS

Fewer than one in eight people with diabetes and hypertension have adequately controlled BP, with remarkable uniformity across studies conducted in a variety of settings. There is an urgent need for multidisciplinary, community-based approaches to manage these high-risk patients.

Prevalence of the metabolic syndrome in the island of Gran Canaria: comparison of three major diagnostic proposals

AIMS

The present study was conducted to estimate the prevalence of the metabolic syndrome in a Canarian population, and to compare its frequency as defined by the most commonly used working definitions.

METHODS

Cross-sectional population-based study. One thousand and thirty adult subjects were randomly selected from the local census of Telde, a city located on the island of Gran Canaria. Participants completed a survey questionnaire and underwent physical examination, fasting blood analyses, and a 75-g standardized oral glucose tolerance test. The prevalence of the metabolic syndrome was estimated according to the definitions proposed by the World Health Organization (WHO), the European Group for the Study of Insulin Resistance (EGIR) and the National Cholesterol Education Program (NCEP), the latter with the original (6.1 mmol/l) and the revised criterion (5.6 mmol/l) for abnormal fasting glucose.

RESULTS

The adjusted prevalence of the metabolic syndrome was 28.0, 15.9, 23.0 and 28.2%, using the WHO, EGIR, NCEP and revised NCEP criteria, respectively. The measure of agreement (kappa statistic) was 0.57 between the WHO and the original NCEP definitions, and 0.61 between the WHO and the revised NCEP definitions. After excluding diabetic subjects, the agreement between the EGIR and WHO proposals was fairly good (kappa=0.70), whereas concordance of the EGIR with the original and the revised NCEP definitions was moderate (kappa=0.47 and 0.46, respectively).

CONCLUSIONS

Whichever the considered diagnostic criteria, the prevalence of the metabolic syndrome in this area of the Canary Islands is greater than that observed in most other European populations.

Factores de riesgo cardiovascular en la población española: metaanálisis de estudios transversales

BACKGROUND AND OBJECTIVE

To review published studies on the prevalence of the main vascular risk factors -hypertension, hypercholesterolemia, diabetes mellitus, obesity and tobacco smoking- in Spain, and to combine their results in an estimate for the Spanish population.

MATERIAL AND METHOD

After a bibliographic search, the studies fulfilling the following inclusion criteria were selected: cross-sectional design, sampling on Spanish population, results including prevalence data of at least one of the above mentioned risk factors, and objective [corrected] (not self-referred) determination of arterial blood pressure, total serum cholesterol, basal glucose, weight, size and body mass index. The combined prevalence was obtained by means of the random effects model, including weight for the proportion that the studied population supposes on the total Spanish population.

RESULTS

Forty-eight studies were identified including a total of 130.945 subjects. According to these studies, the most frequent vascular risk factors were hypertension in the elderly (66.7%, CI 59-74%), overweight/obesity in adult women (48,3%, CI 41-55%) and smoking among men (41.1%, CI 38-44%). In the Spanish population as a whole, 23% showed total cholesterol levels above 250 mg/dl; 33% were smokers (41,1% in men and 24% in women); 34% suffered hypertension; 20% were obese (18% in men and 23% in women); and diabetes affected 8% women and 12% men.

CONCLUSION

Cardiovascular risk in Spain is high. Monitoring the vascular risk factors at a population level is basic for preventive and health care measures.