Uncontrolled blood pressure in T2D participants with (diagnosed or unrecognized) hypertension was associated with male sex, BMI < 30 kg/m2, no previous MI, and study site. Similarly, uncontrolled blood lipid levels in T2D participants with dyslipidemia (diagnosed or unrecognized) were more frequent in men, those who had not suffered MI and attendees of the older DIAB-CORE studies.
Lack of treatment for hypertension was related to younger age, male sex, smoking, BMI < 30, no history of MI or stroke, and study site. Male T2D participants without concomitant hypertension and who had not suffered MI had significantly greater odds of untreated dyslipidemia than other participants in DIAB-CORE.
Socioeconomic features such as educational level and income were not significantly associated with either disease control or pharmacotherapy; lifestyle factors were only associated in some models.
On the one hand, the results of our analyses indicate that the vast majority of patients with T2D in Germany are not adequately treated for hypertension and/or dyslipidemia, even though these conditions have been found to considerably increase the risk of co-morbidities and complications such as MI, stroke, nephropathy and retinopathy.
On the other hand, we confirmed the presumption that patients with additional risk factors, such as advanced age, previous MI, previous stroke or obesity are treated more often for hypertension and dyslipidemia and (apart from those with older age) more frequently achieve adequate blood pressure and lipid target levels. The difference between female and male participants was pronounced and consistent over all sub-analyses.
Strengths and limitations
The essential strength of our study is the large population-based sample drawn from the general German population, aged 45 to 74 years, and the fact that both, laboratory measurements and information on medication intake were available.
Differences in the frequencies of hypertension and dyslipidemia between studies were probably due to the relatively small numbers of affected participants within the individual studies and analyses. Due to the pooling process, only similarly collected and coded data of all six studies could be used and the least common denominator had to be found. Therefore, the definition of diabetes was based on self-report of physician’s diagnosis and treatment with anti-diabetic agents rather than on clinical diagnosis and medical records. Blood pressure was calculated using the mean of the second and third measurements in all studies except for DHS, where only two measurements were performed and used to calculate the mean.
Moreover, measurements of blood pressure and lipids based on a single testing opportunity provide evidence for the respective condition, but are not equal to a clinical diagnosis with repeated measurements. We cannot exclude cases of ‘white coat hypertension’, i.e. elevated blood pressure caused by the excitement of the unfamiliar situation.
Due to compliance issues, women might have reported their medication intake more reliably than men, thus pharmacotherapy in men could have been underestimated and consequently, sex-specific differences overestimated in these analyses.
Patient-centered studies in Germany and other countries have so far examined awareness, treatment, control and factors associated with insufficient control of co-morbidities in patients with and without diabetes. A systematic review by McLean et al. from 2008, which included 26 studies from different countries with 66,833 diabetes patients with co-morbid hypertension, concluded that 83% (range 32-100%) of patients were treated, yet only about 29% (range 5-59%) had their blood pressure controlled to < 140/90 mmHg. The proportions of treatment to control were similar and thus equally insufficient between studies and countries. Unfortunately, the authors did not report person-related factors associated with disease control.
Differences by gender
There are very few studies that have reported factors associated with cardiovascular disease control in patients with diabetes, as opposed to adults in general, irrespective of diabetes status. However, a number of recent studies that focused on gender differences[25–30] found that female patients with diabetes had a worse cardiovascular risk profile and were less controlled compared to their male counterparts. Our study confirmed these results in part; women in DIAB-CORE had higher total cholesterol values than men. However, since HDL-cholesterol values were also higher, the TC/HDL ratio was lower and thus more beneficial in women. In all studies[25–30], blood pressure was higher in women, especially in patients with cardiovascular disease. Although this sex difference was abrogated in some analyses after adjustment for associated variables[27, 28]. There was either no sex difference in the amount of antihypertensive and lipid-lowering medication, or women took more medication, which is in agreement with our study. Furthermore, our results indicate that men are about twice as often unaware of their hypertension and dyslipidemia as women, which is well in line with known gender differences concerning health behaviour. Especially in the age group of about 30 to 60 years, men use health care services less than women and tend to undervalue health care and health behaviour[31, 32]. Several authors hypothesize that societally dominant ‘traditional masculinity’ leads men to adopt beliefs and behaviours that increase health risks and support the ideal of the ‘bulletproof superhero’ who would be embarrassed to check his cholesterol level[33–35].
Influence of age
Findings on the influence of age on hypertension control are controversial (e.g.[36, 37]). An explanation for less control with simultaneously intensified treatment, as seen in our study, might be that resistant hypertension occurs more often in older persons. Accordingly, this association was not detected for dyslipidemia. A cross-sectional study in Sweden examined the assumption that the excess cardiovascular risk of persons with diabetes compared to persons without diabetes decreases with increasing age. However, the authors found that the burden of CVD risk factors clustered over the entire life span with increasing glucometabolic disturbance, especially in older women. Likewise, self-rated health decreased with increasing cardio-metabolic risk and age. The authors suggest that a decreased burden of risk in older patients with diabetes might be due to a survival bias.
Association with body mass index
In our study obese participants (BMI ≥ 30 kg/m2) received medication more frequently and were more often well treated for hypertension, although they were more often affected with hypertension than leaner individuals (data not shown). A Swedish population-based study in hypertensive 60-year-old persons with and without diabetes by Carlsson et al. found an inverse, direct association of high waist circumference with uncontrolled hypertension. The same seems to be true for patients in primary care irrespective of diabetes status. Bramlage et al. found that the odds of good blood pressure control in diagnosed and treated individuals was significantly smaller in overweight and obese primary care patients than in patients with normal weight. Using data of physician diagnosed hypertensive DIAB-CORE participants without diabetes (n = 5012), we found that 29.2% of those with BMI < 25 had controlled hypertension (41.2% were uncontrolled and 29.6% untreated) compared to 28.6% of those with BMI ≥ 30 (50.9% uncontrolled and 20.5% untreated). These results indicate that obese people may be more difficult to treat and obtain goal blood pressure than lean persons; however, they appear to be more aware of their disease. The same seems to be true for a comparison of hypertensive people with and without T2D. Those with T2D are more often treated and well-controlled, much more often treated but not controlled, half as often untreated and half as often unrecognized, irrespective of BMI group (data not shown) than those without T2D. All in all, obese individuals do more often present with a blood pressure ≥ 140/90 mmHg, irrespective of treatment. Thus, people with additional risk factors (such as obesity and diabetes) may be more aware of their blood pressure and more often treated but at the same time, they are more difficult to effectively treat.
Effect of socio-economic differences
We expected to find a significant negative association of high socio-economic status with uncontrolled co-morbidities, however no significant associations were observed with any socio-economic characteristics and the outcome variables. This might, in the case of school education, be due to the unequal frequencies of low (about 80%) vs. high and middle status, which owns to the high mean age of the study population (63 years) and the fact that older people mostly attended junior high school only. In the previously mentioned Swedish study, lack of health care due to low income was independently associated with uncontrolled hypertension in men (OR = 2.71, 95% CI 1.09-6.78) but not in women. In contrast, living in an apartment instead of a house (as an indicator of lower socio-economic status) remained a significantly protective factor in an adjusted model in women (OR = 0.55, 95%CI 0.35-0.85). The authors stated that the finding was puzzling and offered no explanation.
Association with previous cardiovascular disease
Carlsson et al. confirmed that previous cardiovascular disease or coronary heart disease has a protective effect on uncontrolled hypertension, probably because of more intense treatment, better medication adherence and/or symptom relief of angina pectoris.
Influence of more complex factors
There are a number of possible influences on uncontrolled hypertension and dyslipidemia that we could not consider. For example, the Swedish study by Carlsson et al. included data on nutrition and found that daily intake of fruit had an independent, protective effect in men but not in women.
Steckelings, 2004 et al. used data from primary care patients, irrespective of diabetes status (the HYDRA Study: Hypertension and Diabetes Screening and Awareness Study), to describe possible determinants of unsatisfactory hypertension control in Germany. Less than 30% of treated and 19% of all patients, treated or untreated, had controlled blood pressure <140/90 mmHg. The frequency of diagnosis was particularly low in young people, probably due to insufficient blood pressure screening. The authors found that physicians used outdated guidelines and based treatment on diastolic pressure. The great majority of participants (94%) stated that they knew that hypertension is an important risk factor for serious diseases, and most of them (63%) occasionally measured their own blood pressure. However, the physicians participating in the study often misclassified their patients as ‘well controlled’ even though they had BP measurements ≥ 140/90 mmHg.
According to a review by Düsing et al. 2006, more complex, hindering factors could also be insufficient education and motivation provided to the patient by physicians, patients’ reluctance to change lifestyle factors or commence/modify drug treatment, lack of awareness of the risks associated with hypertension, and poor compliance. The latter is a complex and thoroughly explored concept and challenge (e.g.). Apparently, many people with hypertension do not seem to recognize high blood pressure as a progressive chronic illness, but rather misinterpret it as a risk factor in a gamble with a potentially positive outcome[44, 45].
Finally, the sex of the attending physician has been shown to play a role in the quality of risk factor control in patients with hypertension and dyslipidemia. In a cross-sectional study by Journath et al., diabetic men and women achieved goals for blood pressure control, and men achieved goals for cholesterol control more often if they were treated by female physicians. Likewise, a German study including 51,053 diabetes patients treated by 3,096 physicians concluded that female physicians achieved a better quality of care than their male counterparts, especially in risk management important for future disease prognosis.
Differences between Europe and the United States/Canada
Interestingly, there appears to be an intriguing difference in hypertension prevalence and control, irrespective of diabetes status, between Europe and the United States/Canada that has not been appreciated and examined sufficiently. Wolf-Maier et al.[48, 49] compared sample surveys conducted in the 1990s in Germany, Finland, Sweden, England, Spain, Italy, Canada, and the United States and found that even though mean BMI was very similar across these countries, the prevalence of hypertension, defined as blood pressure > 140/90 mmHg or intake of anti-hypertensive medication, differed remarkably. The European average was 44.2% compared with 27.6% in North America. Germany had the highest prevalence with 55.3%. Treatment and control of hypertensive participants within the individual studies was also significantly better in the United States than in Europe with 7.8% hypertension control in the population (29.9% in treated hypertensive participants) in Germany compared to 28.6% (54.5% in treated hypertensives) in the United States.
In order to improve awareness, creative new approaches have been successfully implemented in the United States, e.g. by addressing the issue and counseling black men during a visit at a barbershop. Such innovative ideas might also work in Germany – possibly for younger men with diabetes and no previous cardiovascular complications.