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This paper reviews the US National Institutes of Health (NIH) classification system for prostatitis and summarizes North American data on the incidence and prevalence of NIH category III chronic prostatitis/chronic pelvic pain syndrome, focusing upon a baseline demographic analysis of the US Chronic Prostatitis Cohort Study, a longitudinal study of 488 patients diagnosed with category III prostatitis.
Stamey T, Urinary tract infections in males. In: Stamey T, editor. Pathogenesis and treatment of urinary tract infections. Baltimore: Williams and Wilkins; 1980. p. 342–429.
]. As early as 1980, the National Ambulatory Medical Care Survey reported 20 office visits per 1000 men per year for symptoms compatible with prostatitis [
Koch H, Office visits for male genitourinary conditions. Washington, DC: Office for Health Research, Statistics and Technology, Public Health Service; 1980.
]. Data from the National Center for Health Statistics showed that in the USA in 1985 there were actually more physician visits for prostatitis than for benign prostatic hyperplasia or prostate cancer [
]. Because of the significant impact of CPPS, considerable attention has been directed to elucidating its epidemiology and demographics.
2. Epidemiology
The epidemiology of prostatitis is concerned with understanding the distribution and determinants of the condition. To discuss the epidemiology of prostatitis, a definition is essential. However, the task of defining prostatitis has been confounded by the fact that there are several types of “prostatitis” (bacterial and nonbacterial), each with different characteristics and treatments. The common term “prostatitis” has traditionally been used both in practice and in literature to cover all of these conditions.
3. Definition
The traditional classification of “prostatitis” included acute and chronic bacterial prostatitis, which affect less than 5% of men with prostatitis and for which treatment and management are usually successful [
Stamey T, Urinary tract infections in males. In: Stamey T, editor. Pathogenesis and treatment of urinary tract infections. Baltimore: Williams and Wilkins; 1980. p. 342–429.
]. The majority of patients with prostatitis were traditionally judged to have either nonbacterial prostatitis or prostatodynia. Both of these conditions are characterized by pelvic pain, but only the former is associated with inflammatory cells in the prostatic fluid.
In 1995, a workshop on chronic prostatitis convened by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) of the US National Institutes of Health (NIH) created a new working definition and classification of prostatitis syndromes as follows [
Acute bacterial prostatitis, acute infection of the prostate.
(II)
Chronic bacterial prostatitis, recurrent infection of the prostate.
(III)
Chronic nonbacterial prostatitis/chronic pelvic pain syndrome (CP/CPPS), where there is no demonstrable infection. Subgroups of this class are:
(A)
Inflammatory chronic pelvic pain syndrome, where leukocytes are found in the expressed prostatic secretions (EPS), urine obtained after prostate massage (voided bladder urine-3 [VB-3]), or semen.
(B)
Non-inflammatory chronic pelvic pain syndrome, where no evidence of inflammation is found in the EPS, VB-3, or semen.
(IV)
Asymptomatic inflammatory prostatitis (AIP), where there are no subjective symptoms, but white blood cells are found in prostate secretions or in prostate tissue during an evaluation for other disorders.
Unlike patients in categories I and II, patients with category III prostatitis do not have any detectable colonization or infection of the prostate, as determined by conventional microbiological techniques; abnormalities in the EPS are the primary objective feature of category III prostatitis. Chronic pain is the primary subjective symptom. The majority of patients with “prostatitis” are in category III [
Koch H, Office visits for male genitourinary conditions. Washington, DC: Office for Health Research, Statistics and Technology, Public Health Service; 1980.
The most commonly used measures of disease occurrence (or frequency) in epidemiology are prevalence and incidence. The prevalence of prostatitis refers to the proportion of people who have prostatitis at a specific instance in time. In contrast, the incidence of prostatitis refers to the rate of occurrence of new cases. Of the almost 13 million visits to US urologists in 1991, 5.3% were reported to be for inflammatory diseases of the prostate [
Schappert S. National Ambulatory Medical Care Survey, 1991 Summary. Hyattsville, MD: National Center for Health Statistics. Vital Health Stat 1994;13:116.
]. A community-based cohort study in Minnesota by Roberts utilized data from the Olmstead County study of urinary symptoms and health status among men [
]. In 1992–1996, they found the overall prevalence of physicians’ diagnoses of prostatitis was 11%. In a survey of younger men from the Wisconsin National Guard, Moon et al. found that 5% of respondents reported a history of prostatitis [
]. In a Canadian study, Nickel et al. surveyed 5000 primary care physicians and 545 urologists regarding their practice patterns and this condition and estimated the prevalence to be 9.7% [
]. Among men with a previous diagnosis of prostatitis, the cumulative incidence (the proportion of men without prostatitis in a population who develop the condition over a specified period of time) of subsequent episodes of prostatitis was much higher: 20%, 38%, and 50% among men aged 40, 60, and 80 years, respectively. Few published data are available for the epidemiology of prostatitis outside North America. A population-based study in northern Finland found a high overall lifetime prevalence of prostatitis of 14.2%; of those reporting current or past episodes of prostatitis, 27% experienced symptoms at least once a year, while 16% suffered from persistent symptoms [
5. The Chronic Prostatitis Cohort Study: demographics and baseline analysis
The NIDDK funded the Chronic Prostatitis Collaborative Research Network (CPCRN) in 1997 to conduct basic and clinical research in CPPS. The CPCRN developed a prospective longitudinal Chronic Prostatitis Cohort (CPC) Study and also coordinated the development and validation of a symptom severity index, the Chronic Prostatitis Symptom Index. This index, known as the NIH-CPSI, is an integral component of the symptom measurements within the CPC Study [
The National Institutes of Health chronic prostatitis symptom index: development and validation of a new outcome measure. Chronic Prostatitis Collaborative Research Network.
Leukocyte and bacterial counts do not correlate with severity of symptoms in men with chronic prostatitis: The NIH Chronic Prostatitis Cohort (CPC) Study.
Patient accrual for the CPC Study began on 16 October 1998. All 488 patients who had been successfully screened and enrolled into the CPC cohort prior to closing recruitment on 22 August 2001, were selected for this statistical analysis. The NIH-CPSI, including subscores, was used to measure symptoms. A comprehensive history, physical examination, and demographic profile were obtained from each participant. Generalized Mantel–Haenszel procedures were used to investigate baseline associations between selected factors and symptoms.
5.2 Age
The 488 men in the cohort study had a mean age of 42.8 years (range 30–83 years) and a mean duration of chronic prostatitis of 6.9 years (Table 1). Utilizing case control studies, Berber et al. [
] revealed that cases (n=34) compared to controls (n=50) were more often older (mean age 40 versus 33). A study of the National Ambulatory Medical Care Survey (NAMCS) 1990–1994 revealed that compared to men age 66 and older, prostatitis was more commonly diagnosed in men 36–65 years of age than in men 18–35 years of age [
The age-specific incidence rates for men with a diagnosis of acute prostatitis or prostatitis not otherwise specified (NOS), and chronic prostatitis show different patterns [
]. For men with acute prostatitis or prostatitis NOS, rates were highest between the second and fifth decades, from 3.2 to 3.6 per 1000 person-years, decreased slightly, then increased to 5.4 per 1000 person-years in men in the seventh decade (Fig. 1). For chronic prostatitis, the incidence remained low until the middle of the fifth decade (Fig. 2).
Fig. 1Age-specific incidence rates of acute prostatitis and prostatitis not otherwise specified (NOS; see text for definition) [9].
There is no apparent impact of race on the diagnosis. Analysis of the 1990–1994 NAMCS database revealed no statistically significant trend toward a higher likelihood of prostatitis visits among black men compared to white men [
] (Table 2). The majority of CPC Study participants are white, well educated, and affluent (Table 3). However, lower education, lower income and unemployment were associated with more severe CPPS symptoms. Patient age, duration of CPPS symptoms, race or living status were not significantly associated with overall NIH-CPSI scores. However, the NIH-CPSI score was inversely associated with education. Participants reporting a family income of less than US$ 50,000 yearly had a higher mean NIH-CPSI. Employment status was also significantly related to mean NIH-CPSI.
Table 3Distribution of race, education and employment characteristics and NIH-CPSI by subgroup in 488 CPC Study participants
Table 4 lists summary statistics for NIH-CPSI symptoms, subscores, 24-hour and night-time voiding frequency, and quality-of-life scores. There was a broad spectrum of the CPPS on each subscale as well as the overall CPSI since participant responses varied over the whole range with a median near the midpoint of each scale. Of the 465 participants with complete voiding diary information, 11% had a 24-hour frequency of 15 times or more, and 20% voided at least three times nightly.
Table 4Summary statistics on NIH-CPSI and subscores, SF-12 quality of life score, 24-hour and night-time voiding frequency in 488 CPC Study participants
Patients most frequently reported pain in the perineum and tenderness in the prostate. The most common self-reported diseases were genitourinary (55%), allergies (53%), neurological (40%) and hematopoietic, either lymphatic or infectious (40%). CP/CPPS has a significant negative impact on both mental and physical domains of quality of life. Previous treatments were common. Nearly all (95%) patients reported antimicrobial drug usage. (Among these 488 participants, 280 (57%) reported having used, or currently using, five or more categories of prostatitis-related treatments.) Over half of the patients had undergone cystoscopic evaluation (Table 5). The pain, urinary and quality-of-life subscales as well as overall NIH-CPSI significantly increased (indicating greater impairment) with an increasing number of procedures or treatments.
Table 5Prevalence of previous procedures and treatments for CPPS reported at baseline screening in 488 CPC Study participants
No. (%)
Previous procedures
Cystoscopy
259 (53.73)
Other
164 (34.82)
Bladder hydrodistention
44 (9.69)
Urethral dilation
28 (6)
Chronic pelvic pain syndrome treatment before or at screening
The National Institutes of Health chronic prostatitis symptom index: development and validation of a new outcome measure. Chronic Prostatitis Collaborative Research Network.
Among all 488 men in the cohort study, 50% had urethral leukocytes; and among 397 with EPS samples, 194 (49%) and 122 (31%) had >5 or >10 white blood cells in EPS, respectively. The prevalence of category IIIA ranged from 54% to 90%, depending on the composite set of cut points. None of the CPSI measures were statistically different (p>0.10) for selected leukocytosis subgroups. Based on prostate and semen cultures, 37 of 488 men (8%) had at least one localizing uropathogen. None of the CPSI measures were statistically different (p>0.10) for selected bacterial culture subgroups. Other studies evaluating infectious agents [
] have failed to show that infectious agents have a significant role in CPPS.
6. Conclusion
CP/CPPS is a multifactorial problem affecting men of all ages and demographics. Patients with CPPS have a dismal quality of life, and many have benefited only minimally from empiric, goal-directed therapy. Long-term follow-up of this CPPS cohort will answer important questions about the natural and treated history of this syndrome.
Although men with chronic prostatitis routinely receive anti-inflammatory and antimicrobial therapy, we found that leukocyte and bacterial counts, as we defined them, do not correlate with severity of symptoms. These findings suggest that factors other than leukocytes and bacteria also contribute to symptoms associated with CPPS.Open discussion following the presentation by Dr. Anthony SchaefferDr. John Krieger: Let me just raise the urethritis issue, the question being that there certainly is some overlap between patients with what is called chronic urethritis and patients who met the criteria for the cohort study.Dr. Schaeffer: That is how we designed it. We did not want to exclude those men who had a few white cells but no urethral discharge. In 50% of the patients we found a few white cells; none of them ever had a positive test for chlamydia. But having said that, you are raising the point that some of these gentlemen may have had overt urethritis in the past.Dr. Curtis Nickel: But truly, it would be surprising to find somebody who had inflammation in the prostate gland and no white blood cells further downstream at some point in their day, for example, after ejaculation, voiding, or a bowel movement. I would be surprised if you would find a patient with localization and white blood cells in the EPS who at some point in his 24-hour career of going through life’s tribulations would not have urethral white cells; it is a sampling issue. So you definitely do not want to exclude those patients in a clinical trial or else the results are going to be skewed.
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Epidemiology of prostatitis in Finnish men: a population-based cross-sectional study.
Stamey T, Urinary tract infections in males. In: Stamey T, editor. Pathogenesis and treatment of urinary tract infections. Baltimore: Williams and Wilkins; 1980. p. 342–429.
Koch H, Office visits for male genitourinary conditions. Washington, DC: Office for Health Research, Statistics and Technology, Public Health Service; 1980.
Schappert S. National Ambulatory Medical Care Survey, 1991 Summary. Hyattsville, MD: National Center for Health Statistics. Vital Health Stat 1994;13:116.
The National Institutes of Health chronic prostatitis symptom index: development and validation of a new outcome measure. Chronic Prostatitis Collaborative Research Network.
Leukocyte and bacterial counts do not correlate with severity of symptoms in men with chronic prostatitis: The NIH Chronic Prostatitis Cohort (CPC) Study.
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