What Causes Varicose Veins?
- Posted on: Jun 27 2017
We do know a lot, but not as much as you’d think. We have a good grasp of the risk factors, and we have a pretty good intuition about why these risk factors are risky–which may be good news for patients who hope to avoid the condition or repeat treatment. But for doctors like me who seek the next breakthrough in vein treatment, or for patients who are simply curious, it is surprising how little we know about the basic causes. Much to my amusement, our lack of insight was underscored with a recent article in the Journal of Vascular Surgery.
The risk factors are clear enough. We know there is a strong hereditary component (your odds go to 90% if both parents have them) and that they are associated with obesity, multiple pregnancies (the more the worse), and prolonged standing. They are more common in northern Europeans, women, and in the left leg. Diets and pills do not prevent them. Good news! -.crossing your legs does not cause varicose veins.
Looking at these factors, it is easy to see some common themes: (1) pressure on the veins from above (obesity, prolonged standing and pregnancies) and (2) hormones (pregnancy and women). However, as researchers love to point out, “correlation is not causation” [e.g., just because drinking a lot of coffee is correlated with an increased incidence of prostate cancer does not mean that coffee is the cause.] These observations simply beg the question: Why, exactly, do heredity, pressure and hormones create varicose veins?
Turning to laboratory studies, we find that no animal ever gets varicose veins. Moreover, it is not possible to induce varicose veins in animals artificially, whether by adding or removing any particular drug or nutrient. This fact may give great relief to animal rights activists. However, it does complicate the task for researchers, since they cannot work with animal models in the laboratory, and must instead look solely at humans. Practically speaking, researchers study varicose veins that have been surgically removed to determine what factors cause the veins and valves to weaken.
The pioneer in this field of inquiry is Dr. Thomas Wakefield, director of the Conrad Jobst Vascular Research Lab at the University of Michigan. Dr. Wakefield is a gifted physician, accomplished researcher, and lovely person to boot. Every year, Dr. Wakefield and his research fellows report their progress at the meeting of the American Venous Forum, and the discoveries are always interesting. However, each year I am struck by Dr. Wakefield’s inability to identify a convincing “smoking gun.”
As if to confirm my impression, Dr. Wakefield recently published a summary of the most promising approaches to this vexing issue. He surveys a motley crew of suspects –elastin and collagen gone awry due to a host of enigmatic enzymes and genes such as Delta-like ligand 4, Hey 2, IncRNA-GASS, annexin A, CLUT1, CA9, VEGF, BNIP3, TIMP1, and MMP-9 and many, many others. However, his concluding paragraph says it all:
Varicose veins are a complex and multifactorial disease, and it remains an open question as to which inciting factor is responsible for their development, if any one particular factor is in fact solely responsible. It is unclear whether local dysfunction in the vein wall leads to valvular incompetence or whether the reverse is true. Given the varied environment, genetic, histologic, and hemodynamic factors demonstrated in the literature, it is likely that [the cause of varicose veins] results from an imbalance in more than one of these factors.
In other words, we just don’t know.