Strong social gradient in the metabolic syndrome

There is a strong social gradient in the metabolic syndrome, which is not caused by differences in psychosocial or lifestyle factors.

It is well documented that individuals with higher social status have lower risk of coronary heart disease (CHD). This is generally not explained by differences in lifestyle factors such as smoking and lack of exercise. It has been suggested that some of the social gradient in CHD is caused by differences in psychosocial factors such as perceived stress, depression and lack of social network.

This study explores the socio-economic gradient in the metabolic syndrome and whether this is explained by differences in psychosocial factors or lifestyle factors. Results are based on examination of 6038 randomly selected healthy men and women in the Copenhagen City Heart Study, conducted in 2001-2003 in Copenhagen, Denmark.

Approximately 20% of study individuals had metabolic syndrome but among individuals with highest level of education (of five levels) only 10% had metabolic syndrome whereas among individuals with the lowest level of education 26% had metabolic syndrome. These percentages were similar in men and women.

Individuals with higher level of education were at considerably lower risk of having all of the factors included in the metabolic syndrome: abdominal obesity, hyper-lipidemia, hypertension, high blood-glucose, c-reactive protein and fibrinogen. We explored distribution of psychosocial factors and found that individuals with lower level of education scored higher on depression/fatigue scale and had poorer social network but there was no difference in reporting of perceived stress. As in most other studies, individuals with higher level of education tended to have a healthier lifestyle: they smoked less and exercised more but also drank more alcohol.

When combining the factors in the metabolic syndrome, individuals with the highest level of education had 68% lower risk of having the metabolic syndrome than individuals with the lowest educational level. Surprisingly, this difference was not explained by differences in lifestyle or psychosocial factors: when taking these factors into account individuals with highest level of education still had 60% lower risk of having the metabolic syndrome. This is equal to a 2.5 higher risk of metabolic syndrome in the lowest socio-economic position compared to the highest.

In conclusion, this study confirms that cardiovascular risk factors tend to accumulate with lower socio-economic position. This is particularly true for the cluster of risk factors in the metabolic syndrome. Although both psychosocial stressors and life-style factors such as smoking, lack of exercise and alcohol consumption are important in linking social position and cardiovascular health, these risk factors do not offer simple answers for how individuals at lower social positions are at increased risk for the metabolic syndrome.