The Women’s Health Study has found that women who have high blood pressure levels are three times more likely to develop diabetes than women with low blood pressure levels.
This effect was independent of body mass index and other conditions that are known to predispose people to cardiovascular disease and diabetes.

The researchers from the Brigham and Women’s Hospital, Harvard Medical School and the Harvard School of Public Health, USA, followed over 38,000 female health professionals for ten years.
At the start of the study in 1993, all the women were free of diabetes and cardiovascular disease. Follow-up continued to the end of March 2004.

The researchers divided the women into four groups: those with optimal blood pressure ( BP ), below 120 mmHg systolic, 75 mmHg diastolic; those with normal BP ( 120-129 mmHg systolic, 75-84 mmHg diastolic ); those with high normal BP ( 130-139 mmHg systolic, 85-89 diastolic ); and those with established hypertension ( at least 140 mmHg systolic, 90 mmHg diastolic, and/or self-reported history of hypertension or treatment for the condition ).

After 10 years of follow-up 1.4, 2.9, 5.7 and 9.4% of women in the four categories respectively had developed type 2 diabetes.
After adjusting for various factors such as age, ethnicity, smoking, alcohol intake, body mass index ( BMI ), exercise, family history of diabetes etc, the researchers found that women with hypertension had a three-fold risk of developing diabetes compared with women with optimal blood pressure.

. Researchers found that obesity was also a strong and independent risk factor for the development of type 2 diabetes. However, statistical analyses showed that the relationship between blood pressure and the onset of type 2 diabetes was similar among women who were normal weight, overweight or obese.
There was a three-fold increase in risk from the lowest to the highest BP category within all three weight categories.
This analysis showed that the association between blood pressure and diabetes was not explained by weight alone.

Women who had an increase in blood pressure during the study also had an increased risk of developing diabetes. Those whose blood pressure rose but who remained within the range of normal blood pressure had an increased risk of 26% compared to women who had stable or decreasing blood pressure. Women who progressed to hypertension had a 64% increased risk.

Compared with an overall rate of 4.5 events per 1,000 person-years, the incidence rates in the optimal BP category was 1.5 events per 1,000 person-years, showing that these women have a very low risk of developing diabetes. On the other hand, women with high normal BP had a much higher risk compared with women with normal BP, and the risk among those with established hypertension was substantial: after ten years almost 10% of these women had diabetes, a rate of ten events per 1,000 person-years.

The authors suggest a possible mechanism for the relation between bllod pressure and diabetes may be endothelial dysfunction.
The progression of endothelial dysfunction may cause worsening of both blood pressure and blood glucose.

In conclusion “ The findings provide strong evidence that blood pressure and progression of blood pressure are associated with an increased risk of diabetes. They highlight the fact that cardiovascular risk factors are interrelated and occur in clusters.

Source: European Heart Journal, 2007

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