In our present study of patients treated with primary PCI for STEMI the prevalence of diabetes was higher in older women compared to similarly aged men. In younger patients, however, we found no differences between men and women. Also, in patients without diabetes, a higher admission glucose could only be demonstrated in older women as compared to older men. Both diabetes and increased admission glucose in patients without diabetes, were associated with a higher one-year mortality in both women and men.
Our study confirmed the increased prevalence of diabetes and acute hyperglycemia in women compared to men [5–7]. A new finding however in STEMI patients is that this association is age-dependent and only present in the older age-group. Diabetes (both known and unknown) confers to a greater risk for adverse cardiovascular events in women than in men [6, 7]. Therefore, the increased risk induced by diabetes in patients presenting with STEMI is predominantly observed in older women.
In assessing the risk of adverse events in patients presenting with STEMI, both age and gender are important factors to consider. Importantly, the increased prevalence of diabetes in older women compared to older man is part of a different risk profile. Consistent with the literature, we found that men more frequently had ischemic heart disease in the medical history [6, 7]. Hypertension however was more common in both older and younger women, and this is interesting because hypertension has been associated with the development of diabetes [13–15]. Hypertension may be an early sign of microvascular disease and increased risk of pre-diabetes and STEMI in (aging) women. The association between hypertension and diabetes is also important, since both risk factors induce microvascular and more diffuse coronary artery disease, which is more prevalent in older women [16–19].
Our findings may have implications for medical treatment for patients with STEMI, since it has been shown that some antiplatelet drugs are more effective in patients with diabetes [20, 21]. Particularly since older women with abnormal glucose metabolism have a worse prognosis, optimal medical treatment is mandatory in this subgroup.
It is important to discriminate diabetes from acute hyperglycemia at admission [1, 22]. High admission glucose in patients with diabetes is mainly due to glucose intolerance in the setting of diabetes. Whereas in patients without diabetes, hyperglycemia is probably associated with acute stress, induced by abnormal hemodynamics [1, 23, 24].
There are several explanations for the increased prevalence of acute hyperglycemia in older women without diabetes. Firstly, although we excluded patients with increased HbA1c, several older women may have had abnormal chronic glucose metabolism. Therefore, women are more susceptible for hyperglycemia in response to a stressor, as compared to patients with completely normal glucose metabolism. Secondly, older women with STEMI may have had more acute stress as there is evidence that women more often present with cardiogenic shock compared to men . Also, in our study population older women had more often signs of heart failure on admission as compared to older men, whereas in the younger age group there was no difference in heart failure between men and women. However, after adjustment for the observed differences in heart failure, we found that older women still had increased admission glucose levels. Finally, gender-differences to stress in STEMI patients may be more present in elderly woman than in similarly aged men.
Our study has several limitations. The number of patients in some subgroups were small, and the study was not powered to detect small differences between these subgroups. Also, the sample size was too small to demonstrate survival differences between men and women within the different age groups. Information regarding renal failure, liver failure, obesity, physical activity, inflammatory markers and socioeconomic status were lacking. Therefore, we were unable to adjust for these potential confounders. Finally, our data cannot be extrapolated to non-STEMI patients,non-cardiac patients admitted to intensive care wards, or unstable patients since our study included only STEMI patients and only 8% of these patients had a killip class higher than 1.