Blood pressure and heart rates/pulses that are on the lower end of normal or even a little lower than normal are common findings in people with Down syndrome (see this article on hypertension and hypotension and this blood pressure study). Much of the control of our heart rate and blood pressure is through the autonomic nervous system (the part of the nervous system that controls body functions without us thinking about them). The findings of lower blood pressure and pulse seem to be due to differences in the function of the autonomic nervous systems of people with Down syndrome. Most people with Down syndrome do not experience negative effects from these findings. In fact, a positive of this difference is that hypertension (high blood pressure) is an infrequent finding in people with Down syndrome.
When blood pressure and pulses are too low
Blood pressure and pulses that are too low can be problematic for some people with Down syndrome. When the heart rate and blood pressure go too low, an individual can pass out or faint. This is called syncope. Often, this is due to the differences of the function of the autonomic nervous system. When we are in pain, frightened or anxious it is typical for our pulse and blood pressure to go down and we may pass out (vasovagal syncope). This response appears to be exaggerated or heightened in some people with Down syndrome.
Causes of syncope (fainting)
It is important to remember that not all syncope in people with Down syndrome can solely be explained by differences in autonomic nervous system function. Additional factors need to be considered.
Dehydration: Our experience is that many people with Down syndrome don’t drink enough fluids and are often (at least mildly) dehydrated which can contribute to syncope. When someone is dehydrated, a normally functioning autonomic nervous system will respond by raising the heart rate and blood pressure. In people with Down syndrome, these compensatory measures also seem to be different, less sensitive, or less functional. Therefore, additional factors like dehydration will increase the chance that a person with Down syndrome will faint. For many people with Down syndrome this is not a serious underlying condition, and it can be managed with drinking more fluids and not restricting salt. Our Tips for Staying Hydrated article shares ways to drink more fluids.
Heart disease: Heart disease can be a cause of syncope. Some individuals will have a heart rate that is so slow due to heart disease that more intervention is required. Some individuals will require the implantation of a pacemaker. Some young people with Down syndrome and congenital heart disease will require pacemakers as a complication of their congenital heart disease. As people with Down syndrome are living longer, we are also seeing some of our older adults develop more severe changes in the function of the control of their heart rate. As we age, many people’s bodies are not able to maintain a normal heart rate as easily. This appears to be true for some older people with Down syndrome as well. This can occur in both individuals with congenital heart disease and without a history of congenital heart disease. Additional information is available in this article on atrioventricular septal defect and this study on sinoatrial node disease.
Depending on the symptoms, the severity of the low heart rate and blood pressure, and the person’s other health conditions, a pacemaker may be recommended. In our practice, as we have seen more and more older adults with Down syndrome, we have seen more adults with Down syndrome require pacemakers. In our experience, the insertion of a pacemaker can generally be done safely in people with Down syndrome but a discussion with the person’s health care team (primary doctor, cardiologist, and possibly cardiovascular surgeon) to review the indications of implanting the pacemaker, the overall health of the individual, and the risks of the procedure is recommended.
Other conditions: Other conditions that can be associated with a lower heart rate, blood pressure, or both leading to syncope include anemia and hypothyroidism. An assessment for these conditions and perhaps other conditions should be done. For some for whom these other conditions have been assessed and addressed, who still tend to have low blood pressure and syncope, medications can be prescribed to raise the blood pressure.
There are conditions that can cause syncope that are not related to the heart. Moyamoya disease is a vascular condition in the brain that is more common in people with Down syndrome. It can present as syncope, but it is not necessarily associated with low heart rate or blood pressure.
Connection to Alzheimer's disease?
One additional finding is that there also may be a connection between low blood pressure and Alzheimer’s disease. The nature of the connection has not been determined yet. Does low blood pressure contribute to the onset of Alzheimer’s disease? Does developing Alzheimer’s disease impair the body’s ability to control blood pressure and pulse? We do know that both low blood pressure and Alzheimer’s disease occur more commonly in people with Down syndrome. However, it is not clear that one causes the other.
In our experience, we have seen a number of people with Down syndrome who developed Alzheimer’s disease who also developed abnormally low heart rates and blood pressures that required treatment. However, like the question of the chicken and the egg, it is often not clear which came first, or which may have caused the other. We do suspect, in at least some individuals, the development of Alzheimer’s disease not only results in impaired cognition but also in impairment of the autonomic nervous system leading to symptoms associated with lower heart rate and pulse.
This article was adapted from a Q&A developed in partnership with LuMind IDSC Foundation. This Q&A is available for free along with other Q&As at www.myDSC.org.