The project “Lindavista Study” is a multiple intervention trial on cardiovascular risk factors, encompassing a convenience sample of urban middle-class Mexico City inhabitants, with two parallel arms, one where therapeutic interventions were conducted by cardiologists and the second group where such interventions were made by general practitioners in primary care clinics or private offices. For the purpose of this paper we present the data from both groups.

The hypothesis of the study was that intensive care could abate in 20% the combined mortality of stroke and coronary events in ten years. When the study began in 1995, the rate of such combined mortality in Mexico was 372.7 per 100,000 persons, corrected for age.

Using the equation for sample size calculation for proportions, and assigning a value of α of 0.01, and a power of 90%, it was estimated a total sample size of 1084 subjects per group, but anticipating a 20% of losses at follow-up, we recruited 2602 subjects. All subjects were recruited and signed informed consent at Hospital 1o. de Octubre ISSSTE and randomly assigned to study groups.

The protocol was approved by Ethics and Research Institutional Committees and the study was conducted according to standards derived from the Declaration of Helsinki,16 the Mexican Federal regulations17 and the recommendation guidelines of Good Clinical Practice.18

Recruited subjects were aged 35 or older, of either gender, with no history or current clinical manifestations of vascular disease, who accepted to voluntarily participate in the study over a period of no less than 10 years. All participants underwent medical history and complete physical examination.

Using a validated questionnaire, demographic data were recorded (gender, age, marital status, education level, employment and income), as well as familial and personal history of dyslipidemias, hypertension, diabetes, obesity and/or cardiovascular events. Smoking status was also registered, including the magnitude of daily consumption; nicotine dependence was quantified with the Fagerström scale.19 For the purpose of this survey, passive smoker was defined as a non-smoker person inhaling secondhand smoke produced by smokers within his/her vicinity (home or labor place) for at least eight hours.

Body weight was measured, in kilograms, with a calibrated clinical scale, and height was measured, in meters, with a wall-stadiometer; the body mass index (BMI) was calculated dividing the weight between the squared height. Waist (abdominal) circumference was measured with a fiberglass tape, midway between the last rib and the iliac crest20; the result was registered in centimeters.

Blood pressure (BP) was determined, by qualified personnel, with a calibrated mercury sphygmomanometer, in accordance to the recommendations of the American Heart Association.21 Systemic arterial hypertension (SAH) was diagnosed when BP was ≥140/90 in three visits. Blood chemistry determinations were made exclusively in venous blood. The techniques for collection and sample processing, and the measurements of lipids and lipoproteins, were made according to the Mexican Association for the Prevention of Atherosclerosis and Its Complications (AMPAC) guidelines.22 Total cholesterol (TC), high density lipoprotein cholesterol (HDL-c), and triglycerides (TG) were determined using colorimetric assay kits, and according to the manufacturer's instructions. Low-density lipoprotein cholesterol (LDL-c) was calculated using the Friedewald formula23; in subjects with TG values higher than 400mg/dL, the “non-HDL cholesterol” (CT-HDL-c)24 was used instead.

For every variable, except abdominal circumference, we used the cut-off points established in the latest recommendations of the Adult Treatment Panel III (ATP-III) of the National Cholesterol Education Program (NCEP),24 the American Diabetes Association,25 and the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7).26,27 Overweight was diagnosed with a BMI greater than 25 and less than 30kg/m2, and obesity when BMI was ≥30kg/m2. LDL hypercholesterolemia was considered when LDL-c was above the established for each of the Framingham risk categories28; hypertriglyceridemia was diagnosed when TG≥150mg/dL, and hypoalphalipoproteinemia when HDL-c was <40mg/dL in both genders. According to the American Diabetes Association,25 fasting blood glucose (FG) level was considered normal when it was less than 100mg/dL; a diagnosis of impaired fasting glucose was established with glycemia between 100 and 125mg/dL and, of diabetes mellitus, when glycemia was ≥126mg/dL. Two atherogenic indices were also calculated, as following: TC/HDL-c or LDL-C/HDL-c.29 For abdominal circumference, the specific cut-off points established for Mexicans were taken into account: ≥80cm in women, and ≥90cm in men.30

Finally, based on the Framingham regression equations,31 the absolute risk of nonfatal myocardial infarction and coronary death at 10 years was estimated, and subjects were further categorized in the three ATP-III original categories of risk (<10%, 10–20% and >20%).24

Table 1 shows the frequency in each variable. Age range was 35–76 years of age (mean 50±10 years). Approximately 70% of the subjects had high school or higher education, reflecting middle and upper middle-income social stratus. About 40% of the participants had income 10 times higher than Mexico's minimum wage at the time of recruitment.

Results (Table 2) show that approximately 75% of the subjects (both genders) were overweight or obese; 88% of the women had an abdominal circumference≥80cm, while 74% of the men had a circumference≥90cm.

The frequency of smoking in the studied sample was shown in Table 3. 47% of women and over two-thirds of the men had, or had had contact with cigarette smoke. The prevalence was higher in men than in women. About 5% of the subjects were considered passive smokers. The majority of the active smokers reported a reduced number, i.e., less than 5, of cigarettes daily. Dependence was higher in men.

Hypertension was present in 841 participants (32%) had hypertension. Of the total diagnosed as hypertensive, 272 subjects (32%) were unaware of their condition; within the 569 (68%) that were aware, 479 (56%) claimed to regularly consume an antihypertensive drug, but only 175 patients (36% of those treated and 20% of the entire hypertensive population) had good control of their systemic arterial blood pressure, i.e., below 140/90mmHg for systolic and diastolic pressures, respectively (Fig. 1).

Figure 1.

Percentage of hypertensive subjects in the sample (insert). Relative awareness, treatment and control rates in hypertensive subjects.

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Hundred-sixty patients (6%) were diagnosed with diabetes mellitus. In addition, 385 subjects (14.7%) showed abnormal fasting blood glucose.

Table 4 shows the distribution of the study sample according to their serum lipids and lipoproteins levels. About 36% of participants had borderline total hypercholesterolemia, while 30% had elevated levels of serum total cholesterol. Although TC gender differences were not significant, there was a higher proportion of women with hypercholesterolemia≥240mg/dL. Of all participants, 62% had HDL-c values <40mg/dL. Women had a lower proportion of hypoalphalipoproteinemia than men (52 vs. 78%). Only a small percentage of subjects, mainly women, had HDL-c≥60mg/dL. Ten percent of subjects had optimal values of LDL-c (≤100mg/dL); 25% had near to optimal (110–129mg/dL), 31% borderline (130–159mg/dL), 20% high (160–189mg/dL), and only 14% had very high (≥190mg/dL) levels. Only in a small percentage of the subjects it was necessary to calculate the value of “non-HDL cholesterol”; in 55% of these people, the results were very high, ≥190mg/dL. Slightly less than half the women and nearly two-thirds of the men had values of TG≥150mg/dL. The mean levels of lipids and lipoproteins also are shown in the same table. TC was above the acceptable level of 200mg/dL; HDL-c level in women was significantly higher than in men. LDL-c was about 150mg/dL, without statistical differences between genders. TG was above the normal limit of 150mg/dL, and more elevated in men. Coronary risk, as assessed by atherogenic ratios, was high in both groups, but significantly higher in men than in women. Nevertheless, few patients were stratified in the elevated risk category according to the Framingham score. Fig. 2 shows the collection of cardiovascular risks factors in the study sample: as can be seen, most participants presented from one to three risk factors.

Figure 2.

Relative presence of cardiovascular risk factors (age, systemic arterial hypertension, dyslipidemia, smoking, obesity, and diabetes) in the sample.

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More than half the individuals were diagnosed with MS. Among the cohort, the most common concurrent components of the syndrome were abdominal adiposity and low HDL-c (Fig. 3).

Figure 3.

Relative presence of metabolic syndrome markers in the sample.

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