Hernias happen when tissue or an organ pushes through a weak spot in the muscle or connective tissue that normally holds it in place. The most common version is an abdominal wall hernia, where something inside the abdomen bulges outward through a gap in the surrounding muscle. This weakness can be something you’re born with, something that develops over years of wear, or something created by surgery. The reasons vary by hernia type, but they all come down to two factors working together: a structural weak point and enough pressure to push through it.
How the Abdominal Wall Fails
Your abdominal wall is a layered structure of muscle and connective tissue that keeps your organs contained. Certain spots in this wall are naturally thinner because they have built-in openings for blood vessels, nerves, or other structures to pass through. These natural gaps are where most hernias form.
In men, the tubes that carry sperm travel from inside the abdomen through an opening in the groin called the inguinal canal. This is the single most common site for a hernia. Inguinal hernias account for the vast majority of cases, and men develop them far more often than women. Lower in the groin, blood vessels pass from the abdomen into the legs through another opening, and hernias can form there too (these are called femoral hernias, and they’re more common in women). The belly button is another vulnerable spot, since the abdominal wall never fully closed after the umbilical cord detached.
Globally, inguinal, femoral, and abdominal hernias affect an estimated 32.5 million people at any given time. Older adults carry the heaviest burden, with roughly 3.62 million prevalent cases among people over 60 in 2021 alone. Older men consistently show higher rates than older women.
Pressure: The Force That Pushes Things Through
A weak spot alone doesn’t always produce a hernia. What tips the balance is increased pressure inside the abdomen that forces tissue outward through that gap. Several everyday situations raise this internal pressure:
- Chronic coughing repeatedly drives pressure against the abdominal wall, making it one of the most well-established hernia triggers.
- Straining during bowel movements from chronic constipation creates the same kind of sustained downward force.
- Carrying excess weight adds constant pressure against the abdominal wall. People with a BMI over 30 have significantly higher hernia rates.
- Heavy lifting spikes abdominal pressure, especially when combined with breath-holding.
- Pregnancy stretches and thins the abdominal wall while the growing uterus pushes outward. Umbilical hernias are a recognized complication both during and after pregnancy.
Think of it like a tire with a thin spot in the sidewall. Normal driving might be fine, but hit a pothole hard enough and the inner tube bulges through. Chronic coughing, straining, or carrying extra weight is the equivalent of hitting that pothole over and over.
Genetics and Connective Tissue Quality
Not everyone exposed to the same pressures gets a hernia, and genetics help explain why. Your abdominal wall’s strength depends heavily on collagen, the protein that gives connective tissue its structure. Two types of collagen are especially important: type I provides rigidity, while type III provides flexibility. The ratio between them matters.
Research published in the journal Gut identified a specific gene (COL3A1) that encodes type III collagen as a risk factor for hiatal hernias, particularly in men. People with certain variants of this gene had altered collagen in their tissues, which affected the strength and flexibility of the connective tissue holding things in place. This same gene plays a role in wound healing, which connects to why some people heal poorly after surgery and develop hernias at the incision site.
If your parents or siblings have had hernias, your own risk is higher. The connective tissue you inherit sets your baseline vulnerability, and then life circumstances determine whether that vulnerability ever becomes an actual hernia.
Hernias After Surgery
Incisional hernias form at the site of a previous abdominal surgery where the wound didn’t heal with full strength. They’re surprisingly common, occurring in 9 to 38% of patients after abdominal incisions depending on the type of surgery and the patient’s risk profile.
Wound infection is one of the strongest predictors. Patients who develop a surgical site infection are about 1.9 times more likely to develop an incisional hernia afterward, with 36% of infected patients eventually developing one compared to 19% of those who healed without infection. Obesity compounds the risk: people with a waist circumference over 100 cm (about 39 inches) face notably higher odds. Patients who had a temporary stoma (an opening created during bowel surgery) saw hernia rates as high as 59% at the stoma wound site.
These numbers explain why surgeons pay close attention to wound closure technique, infection prevention, and sometimes place reinforcing mesh during the original operation in high-risk patients.
Hiatal Hernias: A Different Location, Similar Logic
Not all hernias involve the abdominal wall. A hiatal hernia occurs when the upper part of the stomach pushes upward through a small opening in the diaphragm, the flat muscle separating your chest from your abdomen. Your esophagus normally passes through this opening (called the hiatus) on its way to the stomach. When the surrounding muscle weakens, the stomach can slide up through the gap into the chest cavity.
The diaphragm weakens with age, which is why hiatal hernias become increasingly common in older adults. Some people are born with an unusually large hiatus, giving the stomach more room to migrate. Repeated vomiting, intense coughing, straining, and heavy exercise can all accelerate the process by putting sustained pressure on the diaphragm. Injury from trauma or certain chest and abdominal surgeries can also damage the area enough to allow a hernia to develop.
Hiatal hernias often cause acid reflux because the normal angle between the esophagus and stomach changes when the stomach shifts upward, making it easier for stomach acid to flow the wrong direction.
Age and the Gradual Weakening Process
Age is one of the strongest risk factors across all hernia types. Collagen production slows as you get older, and the collagen you do have becomes less organized and weaker. Muscles lose mass and tone. The combination means that the same abdominal wall that held up fine at 30 may develop vulnerable spots by 60 or 70.
This aging process explains why hernia incidence climbs sharply in older adults. The global incidence rate among people over 60 is roughly 135 new cases per 100,000 people per year, and the prevalence rate (people currently living with a hernia) reaches about 331 per 100,000. Men are disproportionately affected at every age, likely due to the inguinal canal creating a larger structural vulnerability combined with the male-specific genetic factors identified in collagen research.
When a Hernia Becomes Dangerous
Most hernias are uncomfortable but not immediately harmful. The real danger comes when a hernia gets trapped. If tissue pushes through and can’t slide back in, it becomes incarcerated. Blood still flows to the trapped tissue at this stage, but if the surrounding muscles squeeze tightly enough to cut off that blood supply, the hernia becomes strangulated. Trapped intestine can begin to die in as little as four hours once blood flow is reduced.
Strangulation is a surgical emergency. Warning signs include sudden, severe pain at the hernia site, nausea and vomiting, the hernia becoming firm or tender, and skin over the hernia turning red or dark. A hernia that you could previously push back in but suddenly can’t is the classic signal that something has changed. This is the main reason many surgeons recommend repairing even painless hernias before they grow large enough for tissue to get stuck.