Caffeine and Detrusor Instability

January 2001; Volume 3; 7-8

By Jean L. Fourcroy, MD, PhD, MPH

Source: Arya LA, et al. Dietary caffeine intake and the risk for detrusor instability: A case-control study. Obstet Gynecol 2000;96:85-89.

A recent article by brown university school of Medicine authors examines the association between high caffeine intake and detrusor instability in 259 consecutive women referred for evaluation of urinary incontinence to the urodynamic center. Participants all had symptoms of urinary incontinence, completed a 48-hour voiding diary detailing caffeine and fluid intake, and had undergone a standardized multichannel urodynamic study. The final study population included 131 women with detrusor instability (defined by provocative cystometry and a maximum urethral closure pressure greater than 20 cm of water) and 128 controls, who did not have detrusor instability but had stress incontinence. Women with diabetes, neurologic disorders, on anticholinergic or alpha-adrenergic agonists, or on antagonist medications were excluded from the study. Caffeine intake of < 100 mg/d was defined as minimal, 100-400 mg/d as moderate, and > 400 mg/d as high. Table 1 indicates how the investigators made the calculation of caffeine.

Table 1-Caffeine content calculation
Beverage Caffeine content
Brewed coffee, 5 oz 128 mg
Coffee, instant 66 mg
Iced tea, 8 oz 47 mg
Tea, hot nonherbal, 5 oz 38 mg
Cola soft drinks, 8 oz 24 mg
Cocoa, 5 oz 4 mg
Coffee, decaf, 5 oz 3 mg

The two groups were similar in parity, weight, estrogen status, and number of prior surgical procedures. The mean age of those with detrusor instability was older (55.6 ± 2.3) than those without detrusor instability (45.2 ± 1.2).

Risk factors identified in this study for detrusor instability were age, current smoking, and high caffeine intake. Smoking may be a confounding factor because of its relationship with dietary caffeine intake. Women older than 55 years of age had an increased risk for detrusor instability than women younger than 55 (odds ratio [OR] 1.7, 95% CI 1.03-2.9, P = 0.028). Women with high caffeine intake had significantly higher odds for detrusor instability than women with low caffeine intake (OR 2.7, 95% CI 1.2-5.8, P = 0.006). Controlling for both age and smoking, the adjusted risk was 2.4 (95% CI 1.1-6.5, P = 0.018) for women with high caffeine intake compared with women with minimal caffeine intake. Moderate caffeine intake was not a significant risk.

Although this is an excellent study several things should be noted. Urinary incontinence can be divided intro three major types—urge or detrusor instability (also termed overactive bladder), stress, and mixed. About one third of women will have mixed incontinence symptoms and signs that include elements of both urge and stress incontinence. The incidence of urge incontinence increases with age. The most important risk factors for stress incontinence are vaginal delivery and hysterectomy. It is highly unusual that consecutive patients would not include any patients with mixed incontinence. However, if a decrease in caffeine intake decreases urge symptoms in women with detrusor instability, one can assume that incontinence of mixed category also will respond. The next important study to do would be to test whether a decrease in caffeine intake decreases urinary symptoms. Also, total fluid intake could have an effect on detrusor instability. Future studies should also take into account the total fluid intake; rapid bladder filling has been posited as a detrusor irritant. A woman who is ingesting 400 mg caffeine from 17 cans of cola is filling her bladder more rapidly than someone whose caffeine comes from four cups of coffee. If the effect of caffeine were purely pharmacologic, there would be a significant association between urge incontinence and moderate caffeine intake.

Caffeine is an interesting drug. A little caffeine makes you vigilant and alert while too much causes shaking. High caffeine levels are prohibited in Olympic sports. Symptoms of too much caffeine (usually more than 500 mg/d) include anxiety, agitation, restlessness, insomnia, and a general feeling of being wired. Both caffeine overdose and withdrawal may be associated with headaches. Caffeine withdrawal (which may be precipitated by an intake of less than 250 mg/d) is associated with irritability, lethargy, and occasional nausea.

Caffeine, along with nicotine and alcohol, are the most commonly used drugs worldwide. About 10 billion pounds of coffee are consumed yearly throughout the world and in the last decade there has been an increase in the number of coffeehouses as well as the consumption of coffee. Caffeine long has been blamed for urinary and other symptoms without scientific proof. Gastroesophageal reflux responds to a decrease or avoidance of caffeine, probably by a gastric acid secretion mechanism.1 The effect of caffeine on fibrocystic changes of the breast is controversial.2

Patients with increased urinary frequency, particularly of any inflammatory origin (including interstitial cystitis), have been counseled to decrease intake of caffeine as well as alcohol and spicy foods. Food diaries long have been important in evaluating patients to identify possible food intolerance that could contribute to symptoms.

Why would caffeine have an effect on urinary incontinence? Caffeine may have an excitatory effect on smooth muscle and is thought to cause an increased effect during bladder filling. It has also been shown to induce transient contraction of smooth muscle through the release of intracellular calcium from intracellular storage sites.

The authors are to be congratulated in studying the risks of caffeine and detrusor instability. However, the key follow-up clinical study should be designed to identify whether or not removal of caffeine from the diet improves urge symptoms. Perhaps we should consider decreasing caffeine in the diet of women with urge incontinence prior to considering medication or surgery.

Dr. Fourcroy is Assistant Professor at Uniformed Services University of Health Sciences in Bethesda, MD.


1. Boekema PJ, et al. Coffee and gastrointestinal function: Facts and fiction. A review. Scand J Gastroenteral Suppl 1999;230:35-39.

2. Heyden S, Fodor JG. Coffee consumption and fibrocystic breasts: An unlikely association. Can J Surg 1986;29:208-211.