Abstract
Background:
Factor analysis reduces a set of directly measured variables into a smaller set of underlying factors representing unique statistically independent domains termed “factors.” In middle-aged people, previous factor analyses of the components of the metabolic syndrome have identified two to four factors. Many of these analyses report blood pressure as one of these factors.
Methods:
We performed a factor analysis of the individual continuous components of the metabolic syndrome among 198 men and 203 women comprising 65% of all 75 year olds from the city of Västerås in Sweden.
Results:
The metabolic syndrome comprised two factors. Factor 1, the metabolic factor, consisted of waist circumference, high-density lipoprotein cholesterol, triglycerides, and fasting glucose, whereas factor 2, the blood pressure factor, consisted of systolic and diastolic blood pressure. These two factors explained 58% (factor 1, 31%, and factor 2, 27%) of the total variation in men. The corresponding figures for women were 63% (factor 1, 36%, and factor 2, 27%). Factor 1 was significantly related to a decreased 10 years of survival for men, with a hazard ratio (HR) of 1.30 (95% confidence interval [CI] 1.07–1.58, P = 0.008), and nearly significantly for women, with a HR of 1.27 (95% CI 0.98–1.64, P = 0.071). In a pooled analysis adjusting for sex, known cardiovascular disease, and hypertension, high blood pressure, and current smoking, the HR for factor 1 was 1.20 (95% CI 1.02–1.49, P = 0.026). Factor 2 was not significantly related to survival.
Conclusions:
Factor analysis of the basic variables of the metabolic syndrome among 75 year olds from a general population identified a metabolic factor and a blood pressure factor. The former factor was significantly related to 10-year survival and the relationship remained after adjusting for known cardiovascular disease and hypertension and current smoking.
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