What Are the Main Causes of Varicose Veins?

Varicose veins develop when the one-way valves inside leg veins stop closing properly, allowing blood to pool and stretch the vessel walls outward. That valve failure is the immediate mechanical trigger, but the reasons those valves fail in the first place involve a tangle of genetics, hormones, body weight, daily habits, and simple aging. Roughly one in four adults will develop visible varicose veins at some point, and the condition is far more than cosmetic for many of them.

How Veins Break Down From the Inside

Healthy leg veins push blood upward against gravity using a series of small flap-like valves that open to let blood through and snap shut to prevent it from sliding back down. When those valves weaken or the vein wall around them stretches, blood flows backward (a process called reflux), pressure builds in the vein segment below, and the vessel gradually bulges. The question researchers have debated for years is which comes first: does the valve fail on its own, or does the vein wall weaken first, pulling the valve leaflets apart? Evidence suggests both pathways can operate at the same time. Primary structural changes in the valves can make them leaky, with progressive reflux then damaging the wall; alternatively, focal dilation near valve junctions can widen the vein enough that the valve leaflets no longer meet, and reflux follows as a secondary event.¹

Regardless of which defect kicks things off, the vein wall itself undergoes real structural changes. Compared with normal veins, varicose saphenous veins have significantly larger wall areas and higher amounts of collagen.² The smooth muscle cells that give a vein its tone become irregularly arranged, and collagen fibers infiltrate and disrupt the orderly muscle layers. That loss of organized muscle structure likely reduces the vein’s ability to contract and resist stretching.³ Once the wall weakens and the valve fails, the rising venous pressure accelerates both problems, creating a self-reinforcing cycle of dilation and reflux.

Genetics and Family History

If your parents had varicose veins, your odds of developing them go up substantially. A large prospective study of roughly half a million people in the UK Biobank found that heritable genetic factors account for about 28% of the population variance in varicose vein disease.⁴ That is a meaningful chunk, though it leaves plenty of room for non-genetic contributors. The same study found that the strongest genetic overlap was not with obesity or peripheral artery disease but with a history of deep vein thrombosis, suggesting shared biological pathways between clotting disorders and varicose veins. There was also a notable genetic correlation with height: taller individuals carry a measurably higher genetic predisposition, likely because longer venous columns produce greater hydrostatic pressure in the legs.

These findings matter because they reframe the question of prevention. You can modify your weight or your job, but you cannot modify your genes or your height. For people with a strong family history, managing the modifiable risk factors becomes more important, not less, because the genetic baseline already tilts toward disease.

Age

Aging is the single biggest non-genetic risk factor. Prevalence roughly doubles after age 65, and population studies have documented rates as high as 82% in people aged 71 to 80.⁵ The reasons are straightforward: vein walls lose elasticity over decades of use, valve leaflets stiffen, and the calf muscles that help pump blood upward weaken with age. These changes are gradual, which is why varicose veins often appear first in middle age and worsen over the following decades. The widespread impression that varicose veins are mainly a condition of older adults is largely correct, though younger people with strong genetic loading or other risk factors can develop them too.

Pregnancy and Hormones

Pregnancy is one of the most common triggers. The growing uterus compresses the pelvic veins, impeding blood return from the legs. Blood volume increases by nearly half during pregnancy, and hormonal shifts soften vein walls. Estrogens and progesterone have been shown to facilitate varicose vein development in people already predisposed by factors like family history, prolonged standing, or obesity, and they can worsen existing superficial venous problems.⁶ Functional symptoms like heaviness and swelling often appear years before visible vein dilation, suggesting that hormonal effects on the venous wall precede the structural damage you can see.

The hormonal picture extends beyond pregnancy. Both estrogen and progesterone receptors have been detected in the inner and middle layers of vein walls in both women and men. In varicose segments, estrogen receptors are more abundant than in the healthy portions of the same vein, especially in women.⁷ The exact mechanism through which sex hormones contribute to varicosis is still being worked out, but these receptor-level findings help explain why varicose veins tend to flare during hormonal transitions like pregnancy, menopause, or long-term use of hormone-containing contraceptives.

Who Gets Varicose Veins More Often, Women or Men?

The common belief is that varicose veins are overwhelmingly a women’s problem. Reality is more complicated. Most population-based surveys do find higher rates in women, with prevalence estimates ranging from about 1% to 73% in women and 2% to 56% in men, depending on how the condition is defined and which population is studied.⁸ But a few studies have reported higher rates in men, and some find no significant difference at all.⁵ Part of the discrepancy comes from the fact that men are less likely to seek evaluation for visible leg veins, so they may be undercounted in clinical data. The safest summary: women probably have a somewhat higher overall risk, driven partly by the hormonal and pregnancy-related factors described above, but men develop varicose veins at rates high enough that it is not primarily a female condition.

Obesity and Abdominal Pressure

Carrying excess weight, particularly in the abdomen, creates a mechanical problem for the veins draining the legs. Elevated intra-abdominal pressure acts like a partial roadblock on the venous highway, forcing leg veins to work harder to push blood upward. In obese patients, the clinical stage of venous disease tends to be more advanced than in non-obese patients with comparable underlying vein anatomy, likely because the higher abdominal pressure leads to greater reflux, wider vein diameters, and higher venous pressures.⁹

A telling demonstration of this effect comes from research on people with large abdominal panniculi (the apron of tissue that hangs over the belt line in severe obesity). When the panniculus was physically lifted off the abdomen, the diameter of both common femoral veins and the great saphenous vein increased measurably, and blood flow volume in the left femoral vein rose by an average of about 63 milliliters per minute. In other words, simply removing the mechanical compression of the abdominal tissue immediately improved venous outflow from the legs. The severity of obesity also correlated with the extent of venous disease.¹⁰ This finding highlights that weight loss can have a direct, measurable impact on the forces driving varicose vein progression.

Prolonged Standing and Occupational Risk

Jobs that keep you on your feet for hours are one of the most replicated risk factors in the literature. A 12-year prospective study tracking the entire Danish working-age population found that people in occupations requiring prolonged standing or walking had roughly 1.8 times the risk of being hospitalized for varicose veins compared with workers in other roles. The researchers estimated that prolonged standing at work accounted for more than one-fifth of all varicose vein cases among working-age adults.¹¹ That fraction is surprisingly large for a single occupational exposure. Teachers, nurses, factory workers, retail staff, and chefs are among the groups most affected. The mechanism is simple: standing still defeats the calf muscle pump, so blood sits in the leg veins under the full column of hydrostatic pressure for hours at a stretch.

Sitting for long periods carries a similar, though probably somewhat lower, risk for the same reason: the calf muscles are not contracting. The critical factor is not whether you are upright versus seated but whether your calf muscles are actively pumping. Brief walks, calf raises, or flexing the feet at intervals during long stationary periods all help keep blood moving.

The Calf Muscle Pump and Why Exercise Matters

Your calf muscles act as a secondary heart for the venous system. Every time they contract during walking, they squeeze the deep veins and push blood upward. When this pump is weak, whether from muscle atrophy, a sedentary lifestyle, or neurological conditions, venous pressure in the lower legs stays chronically elevated. A randomized trial showed that a structured exercise program restored calf pump function to a normal range after six months in people with chronic venous insufficiency, improving how effectively the muscles ejected blood from the leg and reducing the amount of blood left pooling after each contraction.¹² The exercise did not reverse the reflux itself, meaning the faulty valves remained faulty, but it improved the hemodynamics enough to matter clinically.

A systematic review of exercise interventions in chronic venous insufficiency confirmed that training improves blood flow mechanics and muscle strength in milder cases, though in severe disease the evidence for improvements in quality of life or reversal of reflux is less convincing.¹³ The practical takeaway is that regular calf-focused movement, whether through walking, cycling, or targeted exercises, can meaningfully offset several of the risk factors discussed above, especially for people whose work or lifestyle involves extended immobility.

Heat Exposure

People with varicose veins frequently report that their symptoms worsen in hot weather, hot baths, or heated work environments, and the physiology backs up the complaint. Heat causes blood vessels to dilate, increases the volume of blood pooling in the legs, and intensifies swelling and discomfort. Cold does the opposite, producing temporary constriction and short-term symptom relief. For workers in high-heat occupations like kitchens, foundries, or outdoor construction in summer, this thermal vasodilation compounds the standing-related risk. Avoiding unnecessary heat exposure to the legs and using cool water rinses are common clinical recommendations for symptom management, though heat does not appear to cause varicose veins on its own in the absence of other risk factors.

Uncommon Causes Worth Knowing About

Most varicose veins arise from the common risk factors already covered, but a handful of rarer conditions can produce them in unexpected settings. May-Thurner syndrome occurs when the left common iliac artery compresses the left common iliac vein in the pelvis, restricting blood flow from the left leg. It can cause deep vein thrombosis, pelvic congestion, and varicose veins, sometimes appearing in young people who would not otherwise be at risk. Case reports describe it presenting in adolescents with painful vulvar and labial varicosities that resolved once the compressed vein was stented open.¹⁴

Klippel-Trenaunay syndrome is a congenital condition involving varicose veins, capillary and venous malformations, lymphatic abnormalities, and overgrowth of bone or soft tissue, usually affecting one limb.¹⁵ People with this syndrome develop varicose veins in childhood or early adolescence, often with an unusual distribution or associated birthmarks. Because the underlying anatomy is abnormal from birth, treatment planning differs substantially from standard varicose vein management.

The Fiber and Constipation Myth

A long-standing theory, popularized in the 1970s, proposed that low-fiber Western diets cause constipation, which in turn raises intra-abdominal pressure and contributes to varicose veins. It is a plausible-sounding chain of logic, and it still circulates in popular health advice. But when it was directly tested in the Edinburgh Vein Study, a general-population investigation, the data did not support it. There was no association between dietary fiber intake, constipation, and the presence or severity of varicose veins.¹⁶ That does not mean fiber is irrelevant to overall health, but “eat more fiber to prevent varicose veins” is not supported by the evidence.

What Happens When Varicose Veins Progress

Left untreated over many years, varicose veins can progress beyond cosmetic concern. The sustained high pressure in the superficial venous system eventually affects the skin and soft tissue around the ankle, the area where pressures are highest. Venous reflux promotes the accumulation and leakage of inflammatory cells across the small blood vessel walls in the skin. Those inflammatory cells remodel the surrounding tissue, increasing the expression of enzymes called matrix metalloproteinases that break down the tissue scaffold.¹⁷

The earliest visible sign of this process is stasis dermatitis: itchy, reddened, sometimes scaly skin around the lower calf and ankle. If the cycle continues unchecked, the skin can break down into venous ulcers, which are notoriously slow to heal and prone to recurrence. Complications of stasis dermatitis also include skin infections, contact dermatitis from topical treatments, and in severe cases, osteomyelitis of the underlying bone.¹⁸ This progression is not inevitable. Most people with varicose veins never develop ulcers. But the risk increases with time, which is one reason vascular specialists often recommend treating significant reflux even when symptoms are mild.

Compression Stockings After Treatment

Compression stockings are a staple of varicose vein management, both before and after treatment procedures. After thermal ablation, one of the most common modern treatments, wearing compression stockings in the first week or so reduces pain compared with skipping them. A meta-analysis of trials comparing post-procedure compression with no compression found that stockings significantly lowered pain scores in the first ten days and modestly shortened the time to return to normal activities.¹⁹ However, compression made no significant difference in bruising, long-term quality of life, complications, or the rate at which the treated vein stayed closed. A randomized trial confirmed the same pattern: less pain in the compression group during the first few days, no difference in clinical severity scores or quality of life at six months.²⁰ For patients who find stockings uncomfortable or impractical, this evidence suggests the consequences of skipping them after a procedure are limited mainly to more discomfort in the first week, not worse long-term outcomes.