UTIs: Causes and Risk Factors

UTI risk factors
© Verywell, 2018 

One of the most common types of infection, urinary tract infections (UTIs), occur when harmful microscopic organisms enter your urinary tract. Although these organisms can include fungi and viruses, most UTIs are caused by bacteria.

Your body typically eliminates these bacteria before they can trigger symptoms, but risk factors ranging from sexual activity to underlying health problems can increase the likelihood of developing a urinary tract infection.

Common Causes and Risk Factors

While a UTI can occur in any part of your urinary system (including the bladder, kidneys, ureters, and urethra), most UTIs affect the bladder and urethra (i.e. the lower urinary tract). Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis are among the bacteria most commonly linked to UTIs.

Gender

Because of certain anatomical factors, women face a much higher risk of UTIs (compared to men). This is because women have a shorter urethra, which allows bacteria to reach and infect the bladder far more easily. What’s more, the opening to the urethra in women is significantly closer to the rectum, where UTI-causing bacteria are known to dwell.

Pregnancy

Due to pregnancy-related changes in the urinary tract, UTIs may also be more common during pregnancy (especially from week six through week 24). It’s said that the increased size and weight of the uterus may prevent the complete drainage of urine from the bladder, which can make pregnant women more UTI-prone.

Menopause

Women who have gone through menopause may also have a greater risk of urinary tract infections, possibly due to hormonal changes that might affect the beneficial bacteria responsible for fighting off harmful microorganisms in the urinary tract.

Health Conditions

Several chronic health problems may increase UTI risk as well.

These include conditions associated with impaired immune response (such as diabetes), which can weaken your body’s ability to fend off bacteria. Age-related issues like Alzheimer’s disease may also factor into UTI risk, since they may interfere with personal hygiene.

In addition, the following people may be more likely to develop urinary tract infections:

  • those with spinal cord injuries or nerve damage around the bladder, which can prohibit complete emptying of the bladder
  • those with kidney stones, enlarged prostate, or any other issue that blocks the normal flow of urine and encourages bacterial growth
  • those with vesicoureteral reflux (VUR) or other abnormalities of the urinary tract
  • those who have recently used a urinary catheter
  • those with bowel incontinence

Genetics

Some emerging research suggests that genetics may play a role in urinary tract infections. In a 2011 report published in the journal Nature Reviews: Urology, for instance, scientists state that genetic variation in immune response may either influence the severity of UTIs or protect against infection. However, more research is needed before the possible genetic causes of UTIs can be fully understood.

Lifestyle Risk Factors

A number of lifestyle factors may contribute to the development of urinary tract infections.

Sexual Activity

Sexual activity is one of the most common lifestyle risk factors for UTIs, particularly for women. It’s thought that sexual intercourse may transport bacteria from the genitals and anus into the urethra and, in turn, lead to infection.

For men, unprotected sexual activity involving women with a vaginal infection may increase risk of UTIs.

Birth Control

Use of certain types of birth control (such as diaphragms or spermicide) may also raise UTI risk in women.

Personal Hygiene

Several personal hygiene habits are also considered risk factors for UTIs. These habits include:

  • use of douches and feminine hygiene sprays or powders
  • wiping from back to front after urinating or having a bowel movement, especially for women
  • retaining urine for an abnormally prolonged period (i.e. “holding it in”)
  • extended periods of immobility (such as during recovery from an injury or illness)

Sources:

Flores-Mireles AL, Walker JN, Caparon M, Hultgren SJ. “Urinary tract infections: epidemiology, mechanisms of infection and treatment options.” Nat Rev Microbiol. 2015 May;13(5):269-84.

Moore EE, Hawes SE, Scholes D, Boyko EJ, Hughes JP, Fihn SD. “Sexual intercourse and risk of symptomatic urinary tract infection in post-menopausal women.” J Gen Intern Med. 2008 May;23(5):595-9.

The National Institute of Diabetes and Digestive and Kidney Diseases. “Bladder Infection (Urinary Tract Infection—UTI) in Adults.” March 2017.

Ragnarsdóttir B, Lutay N, Grönberg-Hernandez J, Köves B, Svanborg C. “Genetics of innate immunity and UTI susceptibility.” Nat Rev Urol. 2011 Jul 12;8(8):449-68. 

U.S. National Library of Medicine. “Urinary Tract Infections (UTI).”