What causes constipation?
Constipation is caused by stool spending too much time in the colon. The colon absorbs too much water from the stool, making it hard and dry. Hard, dry stool is more difficult for the muscles of the rectum to push out of the body.

Common factors or disorders that lead to constipation are

• Diets low in fiber
• Lack of physical activity
• Medications
• Life changes or daily routine changes
• Ignoring the urge to have a bowel movement
• Neurological and metabolic disorders
• G.I. tract problems
• Functional G.I. disorders

Diets Low in Fiber
The most common cause of constipation is a diet with too little fiber. Fiber is a substance in foods that comes from plants. Fiber helps stool stay soft so it moves smoothly through the colon. Liquids such as water and juice help fiber to be more effective.

Older adults commonly do not get enough fiber in their diets. They may lose interest in eating because food does not taste the same as it once did, they do not feel hungry as often, they do not want to cook, or they have problems with chewing or swallowing. These factors may lead an older adult to choose foods that are quick to make or buy, such as fast foods or prepared foods, which are often low in fiber.

Lack of Physical Activity
A lack of physical activity can lead to constipation. Constipation often occurs after an accident or during an illness when a person must stay in bed and cannot exercise. Lack of physical activity is thought to be one of the reasons constipation is common in older adults.

Medications
Medications that can cause constipation include

• Pain medications, especially narcotics
• Antacids that contain aluminum and calcium
• Calcium channel blockers, which are used to treat high blood pressure and heart disease
• Medications that treat Parkinson’s disease—a disorder that affects nerve cells in a part of the brain that controls muscle movement—because these medications also affect the nerves in the colon wall
• Antispasmodics—medications that prevent sudden muscle contractions
• Some antidepressants
• Iron supplements
• Diuretics—medications that help the kidneys remove fluid from the blood
• Anticonvulsants—medications that decrease abnormal electrical activity in the brain to prevent seizures

Constipation can also be caused by overuse of over-the-counter laxatives. A laxative is medication that loosens stool and increases bowel movements. Although people may feel relief when they use laxatives, they usually must increase the dose over time because the body grows reliant on laxatives to have a bowel movement. Overuse of laxatives can decrease the colon’s natural ability to contract and make constipation worse. Continued overuse of laxatives can damage nerves, muscles, and tissues in the large intestine.

Life Changes or Daily Routine Changes
During pregnancy, women may be constipated because of hormonal changes or because the uterus compresses the intestine. Aging can affect bowel regularity, because of a gradual loss of nerves stimulating the muscles in the colon, which results in less intestinal activity. People can also become constipated while traveling, because their normal diet and daily routine are disrupted.

Ignoring the Urge to Have a Bowel Movement
People who ignore the urge to have a bowel movement may eventually stop feeling the need to have one, which can lead to constipation. Some people delay having a bowel movement because they do not want to use toilets outside their home, particularly public restrooms, or they feel they are too busy.

Neurological and Metabolic Disorders
Certain neurological and metabolic disorders can cause food to pass through the digestive system too slowly, leading to constipation. Metabolic disorders, such as diabetes and hypothyroidism, disrupt the process the body uses to get energy from food. Hypothyroidism is a disorder that causes the body to produce too little thyroid hormone, which can cause many of the body’s functions to slow down.

G.I. Tract Problems
Some problems in the G.I. tract can compress or narrow the colon and rectum, causing constipation. These problems include

• Adhesions—bands of tissue that can connect the loops of the intestines to each other, which may block food or stool from moving through the G.I. tract
• Diverticulosis—a condition that occurs when small pouches, or sacs, form and push outward through weak spots in the colon wall; the pouches are called diverticula
• Colon polyps—growths on the surface of the colon that can be raised or flat
• Tumors—abnormal masses of tissue that result when cells divide more than they should or do not die when they should
• Celiac disease—an immune reaction to gluten, a protein found in wheat, rye, and barley, that causes damage to the lining of the small intestine and prevents absorption of nutrients

Functional G.I. Disorders
Functional G.I. disorders are problems caused by changes in how the G.I. tract works. People with a functional G.I. disorder have frequent symptoms; however, the G.I. tract does not become damaged. Functional constipation often results from problems with muscle activity in the colon or anus that delay stool movement.

Functional constipation is diagnosed in people who have had symptoms for at least 6 months and meet the following criteria for the last 3 months before diagnosis:

• Two or more of the following symptoms:
  • straining to have a bowel movement at least 25 percent of the time
  • having lumpy or hard stools at least 25 percent of the time
  • feeling as though stool is still in the rectum after a bowel movement at least 25 percent of the time
  • feeling as though something is blocking stool from passing at least 25 percent of the time
  • using their fingers to help with stool passage at least 25 percent of the time
  • having fewer than three bowel movements per week
• Rarely passing loose stools without the use of laxatives
• Not having irritable bowel syndrome (IBS)