Wednesday May 21 2008
The study followed 2,306 diabetic men for four years
“Men with diabetes who are having trouble keeping an erection could be at increased risk of serious heart problems”, BBC News reported. It said that a study has found that those with erectile dysfunction are twice as likely as other men with diabetes to develop heart disease. This finding could apparently be used to “alert both patients and healthcare providers to the future risk of coronary heart disease”.
This study followed 2,306 diabetic men for four years and found that the men with erectile dysfunction were 1.58 times more likely to have a cardiac event (fatal or non-fatal heart attack or surgery for heart disease). It has some potential weaknesses, for example it might not have used the most accurate method for classifying erectile dysfunction, some of the participants may already have had heart disease before the study began, and other drugs they were taking could have had an effect.
Despite its shortcomings however, this research corroborates what other studies have suggested. It suggests that an assessment of erectile dysfunction could be useful when assessing the risk of heart disease in men with diabetes.
Where did the story come from?
Dr Ronald Ching-Wan Ma and colleagues from the Chinese University of Hong Kong carried out the research. The study was supported by an MSD University Grant and by the Hong Kong Foundation for Research and Development in Diabetes. The study was published in the (peer-reviewed) Journal of the American College of Cardiology.
What kind of scientific study was this?
It is known that men with diabetes have a higher risk of erectile dysfunction and its prevalence increases with age, and duration and severity of the diabetes. Previous research has suggested a close association between erectile dysfunction and atherosclerosis, while other studies have indicated that it could be used as an indicator of coronary, peripheral or cerebrovascular disease.
The authors of this study aimed to be the first to use a prospective analysis to see if the presence of erectile dysfunction can be used as a predictor of adverse cardiovascular events such as coronary heart disease. In this prospective cohort study, the researchers included men with diabetes at the Prince of Wales Hospital Diabetes Centre, Hong Kong between 1995 and 2005. The suitability of 3,640 men who had been referred to the centre was assessed. The researchers excluded any men who had type 1 diabetes, cardiovascular disease at the start of the study (through medical history or abnormal ECG or stress test) or for whom there was incomplete information on erectile dysfunction.
This left 2,306 men with type 2 diabetes who had been assessed for the complications and risk factors associated with their condition. The participants had a series of clinical and laboratory assessments, including at least two urine collections to measure protein levels. This would give an indication of kidney function. In addition, they were asked whether they suffered from erectile dysfunction (they could answer yes or no).
The researchers followed up the participants for an average of four years, during which time they collected data on hospital admissions and mortality. In Hong Kong, all residents have a unique identification number and researchers used this to link hospital records and diagnoses (e.g. death from acute heart attack or other coronary cause, or non-fatal cardiac events) with the participants’ original data from the study. In this way, they could see if there was an association between heart problems and erectile dysfunction in men with diabetes.
When analysing this association, the researchers took into account other factors that can have an influence on erectile dysfunction or heart disease, including; smoking history, age, how long they had diabetes, use of blood pressure and other medications, blood pressure, blood cholesterol, BMI and waist circumference.
What were the results of the study?
The researchers found that at the beginning of the study, 27% of the men reported having erectile dysfunction. These men were older, had higher blood pressure, had had diabetes for longer, and had higher blood cholesterol.
During approximately four years of follow up, new cardiac events occurred in about 5% of men. Men with erectile dysfunction were 1.58 times (HR 1.58, 95% CI 1.08 to 2.30) more likely than men without erectile dysfunction to experience a cardiac event during follow up. This analysis took into account some other factors that might be responsible for the association. Erectile dysfunction was not the only factor that increased cardiac events; age, duration of diabetes, high levels of protein in urine, and use of medications for high blood pressure were also independently associated.
What interpretations did the researchers draw from these results?
The researchers conclude that there is an association between erectile dysfunction and new cardiac events in men with type 2 diabetes. They say that erectile dysfunction is a “surrogate marker” for future heart problems.
What does the NHS Knowledge Service make of this study?
The researchers raise several possible problems associated with this study. These should be kept in mind when interpreting the results:
- Studies that assess sensitive topics such as erectile dysfunction are difficult to carry out accurately. The men who took part might not have fully reported the extent of their erectile dysfunction, leading to an underestimation of the problem. For example, if a large number of men with erectile dysfunction did not report it and were free of cardiac events during follow up, their results may have swayed the conclusions to being not significant. On the other hand, if some men didn’t report their erectile dysfunction and experienced cardiac events, the study will have underestimated the strength of the association.
- The researchers say that the single question they asked to determine whether a man suffered from erectile dysfunction, may not have been as appropriate as using other questionnaires that ask more objective questions. If men with more severe dysfunction were more likely to answer yes, then the study’s findings would be biased.
- The study was carried out in Hong Kong and the men who took part might not be representative of men from other countries. In particular, it’s unclear if the findings from the study are applicable to men in western countries as lifestyle factors across cultures may contribute differently to a person’s overall risk profile.
- Though the researchers tried to exclude any men with evidence of cardiac problems, they say that “comprehensive cardiac assessments were not routinely performed in asymptomatic patients”. This means that people with no obvious clinical symptoms could have been included. If this were the case, the researchers had no way of identifying those whose erectile dysfunction was actually a result of their heart problems.
- This study suggests that there are several independent factors associated with erectile dysfunction – namely age, use of medications, duration of diabetes and high protein levels in urine. Determining which of these is the most important is difficult. Future studies should particularly assess the contributions made by drugs such as lipid lowering statins that are known to cause erectile dysfunction. Most people with diabetes will be on multiple drugs with the potential to cause this condition.
It is known that men with diabetes are more likely to have erectile dysfunction and that this problem is associated with atherosclerosis (narrowing and hardening of the arteries). This study provides data to support the association that other studies have found between erectile dysfunction and cardiac problems. It is important that these results are confirmed in larger populations and across cultures.