Karin Coyne, United BioSource Corporation, Center for Health Outcomes Research, 7101 Wisconsin Avenue, Suite 600, Bethesda, MD 20814, USA. e-mail: firstname.lastname@example.org
To estimate and compare the prevalence and associated bother of lower urinary tract symptoms (LUTS) in the general populations of the USA, UK and Sweden using current International Continence Society (ICS) definitions, as no previous population-based studies evaluating the prevalence of LUTS in the USA, using the 2002 ICS definitions, have been conducted.
SUBJECTS AND METHODS
This cross-sectional, population-representative survey was conducted via the Internet in the USA, the UK and Sweden. Members of Internet-based panels were randomly selected to receive an e-mailed invitation to participate. If interested, respondents selected a link to an informed consent page, followed by the survey. Participants were asked to rate how often they experienced individual LUTS during the previous 4 weeks, on a five-point Likert scale, and, if experienced, how much the symptom bothered them. Descriptive statistics were used to summarize and present the data.
Responses rates for the USA, the UK and Sweden were 59.6%, 60.6% and 52.3%, respectively, with a final sample of 30 000 (USA 20 000; UK 7500; Sweden 2500). The mean age (range) of the participants was 56.6 (40–99) years; the mean percentages for race were 82.9% white, 6.7% black, 6.0% Hispanic and 4.4% Asian/other. The prevalence of LUTS was defined by two symptom frequency thresholds, i.e. at least ‘sometimes’ and at least ‘often’ for all LUTS except incontinence, where frequency thresholds were at least ‘a few times per month’ and at least ‘a few times per week’. The prevalence of at least one LUTS at least ‘sometimes’ was 72.3% for men and 76.3% for women, and 47.9% and 52.5% for at least ‘often’ for men and women, respectively. For most LUTS, at least half of the participants were bothered ‘somewhat’ or more using a frequency threshold of at least ‘sometimes’. For a threshold of at least ‘often’, ‘somewhat’ or more bother was reported by ≥70% of participants except for terminal dribble in men and split stream in women.
In this large population study of three countries, LUTS are highly prevalent among men and women aged >40 years. In general, LUTS experienced ‘often’ or more are bothersome to most people.
LUTS are experienced by individuals with pathology affecting the LUT, including detrusor overactivity, sphincteric weakness, sensory bladder disorders, and BPH , and are generally divided into three groups: storage, voiding and postmicturition symptoms. Storage symptoms (inclusive of overactive bladder, OAB) include increased urinary frequency, nocturia, urinary urgency, and urinary incontinence. Voiding symptoms include slow/weak stream, hesitancy and terminal dribble, whereas postmicturition symptoms consist of incomplete emptying and postmicturition dribble. LUTS also encompass symptoms associated with sexual intercourse and genital and LUT pain.
The prevalence of LUTS has often been assessed in men (and infrequently in women) using the IPSS [2–9]; however, the IPSS was developed for men  and only three of the seven questions ask about bothersome storage symptoms. Also, the prevalence of LUTS associated with the IPSS is typically reported as a summed score (i.e. none = 0, mild = 1–7) rather than by individual symptoms, thereby limiting the ability to consider the prevalence and impact of individual LUTS. Nonetheless, previous research has noted LUTS to be highly prevalent [3,11–13]. As noted by Irwin et al. in EPIC, a large population-based study, the prevalence of at least one LUTS, using the 2002 ICS definitions, was found to be 62.5% in men and 66.6% in women aged ≥40 years. Certainly, not all epidemiological studies have found estimates of LUTS of the magnitude reported by Irwin et al., and the prevalence of various LUTS in community and clinical populations will differ depending on how questions are asked, linguistic interpretation, cultural differences, and what level of severity or frequency was used to determine the presence of the symptom. To illustrate, in EPIC the ICS definition of nocturia (one or more voids/night) yielded a prevalence of 48.6% in men and 54.5% in women; however, when nocturia was defined as at least two voids per night, prevalence rates were 20.9% in men and 24.0% in women.
Importantly, regardless of how researchers define LUTS, from a patient perspective LUTS greatly affect health-related quality of life (HRQL) and are ‘bothersome’ to the men and women who experience them [2,5,14–22]. However, the lack of a consistent definition of bother and the multitude of tools and scoring methods used to assess this construct make it difficult to evaluate rates of bothersomeness across different samples. Thus, there is a need for an assessment of the frequency of individual LUTS and their respective ‘bother’ rating.
Consequently, the objective of the Epidemiology of LUTS (EpiLUTS) study was to evaluate the prevalence and bother of individual LUTS in population-representative samples in the USA, the UK and Sweden, using the most recent symptom definitions created by the ICS [1,23], with modifications as necessary to optimize patient understanding.
SUBJECTS AND METHODS
A population-based, cross-sectional Internet-survey was conducted in the USA, the UK and Sweden to examine the prevalence and symptom-specific bother of LUTS and evaluate the impact of these symptoms on HRQL, work productivity, mental and sexual health. The three countries were selected because an epidemiological investigation of such magnitude for LUTS had not been conducted in the USA; the UK and Sweden were included because they represented the range of LUTS (highest and lowest prevalence) in EPIC . In all, 30 000 men and women aged ≥40 years were targeted for recruitment (20 000 in the USA, 7500 in the UK, and 2500 in Sweden) from three Internet-based panels developed from consumer and voter databases in each country. The rationale for this recruitment approach and study design are described elsewhere , but importantly, each country’s most recent population census was used as the basis for creating a ‘target sample’ to ensure that the data collected would be representative of the general population according to the demographics of age, gender, race and education. Inclusion criteria were: (i) age ≥40 years; (ii) provision of informed consent; (iii) ability to read the local language; and (iv) ability to use a computer and access the Internet. Respondents who reported currently being pregnant or having a UTI were excluded from participation.
Procedures for recruitment were comparable across countries. An e-mail invitation with a uniform resource locator link was sent to panel members. If interested, potential respondents clicked on the link, which directed them to an informed consent screen; consent must have been provided to proceed to the survey. The Internet survey was designed so that participants could omit questions or stop the survey at any time.
The EpiLUTS survey was developed with clinicians and epidemiologists and is based on extensive qualitative research in clinical and community samples of 129 patients with and without a history of LUTS. This research included focus groups and cognitive debriefing interviews to elicit patient descriptions of their urinary symptoms (unpublished). LUTS were defined using ICS definitions  with language modifications to increase lay-person understanding of the questions. LUTS assessed were: storage (urinary frequency, urinary urgency, nocturia, incontinence, as stress, urgency or mixed, and nocturnal enuresis, leaking during sexual activity, and leaking for no reason); voiding (weak stream, terminal dribble, hesitancy, straining, intermittency, split stream); postmicturition (incomplete emptying, postmicturition incontinence); and other (bladder pain and dysuria). The response options for most LUTS were on a five-point Likert scale, i.e. ‘never’, ‘rarely’, ‘sometimes’, ‘often’, and ‘almost always’. For every LUTS frequency response of at least ‘rarely’, participants were asked ‘how bothered’ they were by the particular LUTS. Similarly, bother ratings were assessed on a five-point Likert scale as ‘not at all’, ‘a little bit’, ‘somewhat’, ‘quite a bit’, and ‘a great deal’.
The original questionnaire was written in American English and translated into each country’s primary language following the Good Practice Guidelines for the Translation and Cultural Adaptation Process of the International Society of Pharmacoeconomics and Research Outcomes . Harmonized translations were created in UK English and Swedish through a reiterative process of forward and back translations, and were reviewed by survey research experts and local users. Pilot Internet-surveys and cognitive debriefing interviews were conducted in each country to further assess cultural and linguistic integrity, the ease of the Internet-survey format, and overall content validity.
All participants were asked to complete the following: questions about LUTS frequency and bother, comorbid conditions, sociodemographics, generic HRQL (Short Form-12 ), overall bladder condition (Patient Perception of Bladder Condition ), general healthcare seeking, general risk factors, anxiety and depression (Hospital Anxiety and Depression Scale [28,29]), sexual health (Sexual Quality of Life instrument for females , Abbreviated Sexual Function Questionnaire , Male Sexual Health Questionnaire to Assess Ejaculatory Dysfunction , Index of Premature Ejaculation , Erectile Function domain of the International Index of Erectile Function ), and the IPSS . Disease-specific HRQL (OAB questionnaire short-form ), work productivity (modified Work Limitation scale ), and healthcare-seeking behaviour questions were presented to respondents reporting at least one LUTS during the prevalence questions. Figure 1 illustrates the survey question flow. Because of the skip-pattern format, the number and type of questions asked varied across participants. Upon survey completion, the participant received incentive points for their participation (translating to ≈$2.00 in the USA, £1.50 in the UK and SEK 1.33 in Sweden).
For statistical analysis, sample matching was used to construct population-representative samples of respondents within each country’s Internet-based panel, and poststratification weights were calculated to correct small amounts of imbalance based on differences in response rates. Weights were calculated by raking the completed interviews to the marginals for the matching variables (e.g. age, race, gender and education) before all analyses. All data presented are weighted to each country’s population census. Given the homogenous ethnicity in Sweden, race was not used for sample matching or weighting in the Swedish sample.
Demographic variables were evaluated by descriptive analyses and are presented by gender. The prevalence of individual LUTS was defined by dividing the Likert responses in two ways: (i) ‘never’ and ‘rarely’ vs ‘sometimes’ or more (at least sometimes); and (ii) ‘never’, ‘rarely’ and ‘sometimes’ vs ‘often’ or more (at least often). Bother levels associated with each symptom were analysed by each bother question. Bother was also defined by dividing the Likert responses in two ways: (i) ‘not at all’ and ‘a little bit’ vs ‘somewhat’ or more; and (ii) ‘not at all’, ‘a little bit’, and ‘somewhat’ vs ‘quite a bit’ or more. Correlations between LUTS frequency and bother were examined using Spearman correlations for men and women separately.
Invitations to complete the EpiLUTS survey were sent to 62 301 members of the USA Internet-based panel, 18 558 in the UK and 7291 in Sweden. Data collection started in the USA (5 June 2007 to 8 July 2007) followed by the UK (26 September 2007 to 25 October 2007) and Sweden (29 January 2008 to 2 April 2008). Recruitment periods were extended to recruit sufficient numbers of men and women aged ≥65 years. The number of eligible individuals who responded to the e-mailed invitation was 36 821 in the USA (59.6% response rate), 10 961 in the UK (60.6% response rate), and 3764 in Sweden (52.3% response rate). In all, 7947 participants (5233 USA, 1993 UK and 721 in Sweden) were excluded owing to high rates of missing or inconsistent data, or discontinuation of the survey.
The final sample included 20 000 participants in the USA, 7500 in the UK and 2500 in Sweden who were randomly selected from the pool of completed survey respondents through ‘sample matching’, a process used to construct gender, age, race and education population-representative samples from large panels of Internet-survey responders. Overall, the mean age (sd, range) was 56.5 (10.9, 40–95) years for men and 56.7 (10.5, 40–99) years for women, and most participants were white (men, 82%; women, 83%), reflecting the population demographics of all three countries (Table 1).
Table 1. The demographics of the participants by gender
All numbers are weighted; subgroups might or might not equal total N due to rounding or weighted values.
As expected, all voiding symptoms were more common among men than women, regardless of LUTS definition (at least ‘sometimes’ or at least ‘often’). Storage symptoms, associated with OAB were more prevalent in women than men (Table 2) but, notably, voiding and storage symptoms were common in men as well as women. The prevalence of at least one LUTS at least ‘sometimes’ was 72.3% for men and 76.3% for women, and 47.9% and 52.5% for at least ‘often’ for men and women, respectively. Most participants reported waking to urinate at least once per night (men 69.4%; women 75.8%), and more than a quarter reported two or more nocturia episodes (men 28.5%; women 33.7%). Results for LUTS prevalence classifications according to the symptom frequency category at least ‘sometimes’ and at least ‘often’ were similar, with lower frequencies when the ‘often’ threshold was used (most were about a third of the prevalence found using at least ‘sometimes’). To simplify the results presented here, discussions focus on the ‘at least sometimes’ LUTS presence/absence threshold.
Table 2. A summary of the prevalence of LUTS at least ‘sometimes’ and at least ‘often’, by gender
Condition, n (%)
Frequency of LUTS
at least ‘sometimes’
at least ‘often’
All numbers are weighted; subgroups might or might not equal total N due to rounding or weighted values.
Assessed as dichotomous yes/no variable.
Nocturia episodes are dichotomized ≥1, ≥2, and ≥3 to provide prevalence rates of each variable; nocturia episodes were collected as a continuous variable. Due to grouping by symptom prevalence, nocturia episodes ≥1 and ≥2 were calculated for the LUTS at least ‘sometimes’ group only; nocturia episodes ≥3 were calculated for the LUTS at least ‘often’ group only.
In the LUTS at least ‘sometimes’ group, incontinence episodes occur a few times a month or more; in the LUTS at least ‘often’ group, incontinence episodes occur a few times a week or more.
Symptoms suggestive of BOO due to possible BPH were highly prevalent among men, including voiding symptoms (terminal dribble 45.5%; weak stream 27.0%; hesitancy 20.1%); storage symptoms (nocturia twice or more 28.5%; urgency 22.4%; perceived daytime frequency 20.5%); and incomplete emptying (22.7%). Also common in men were postmicturition incontinence (29.7%), split stream (19.5%) and intermittency (18.7%). Interestingly, men were far less likely to report urgency described as ‘a sudden need to rush to urinate for fear of leaking urine’ (14.0%) compared with urgency not described in relation to leaking (22.4%). Rates of other types of incontinence were generally low among men, with urgency incontinence reported most frequently (9.3%).
Terminal dribble was the most common symptom in women (38.3%). Two other symptoms often described in relation to the prostate in men were prevalent in women, i.e. incomplete emptying (27.4%) and weak stream (20.1%). Storage symptoms were reported frequently, including urgency, the cardinal symptom of OAB (35.7%), nocturia (two or more voids per night, 33.7%), urgency with fear of leaking (33.3%) and perceived frequency (24.6%). Incontinence was also highly prevalent, particularly stress incontinence related to laughing, sneezing or coughing (31.8%), followed by urgency incontinence (24.4%) and postmicturition incontinence (14.9%).
The proportions of those bothered ‘somewhat’ or more and ‘quite a bit’ or more for the respective LUTS classifications of at least ‘sometimes’ are presented in Fig. 2 (men) and Fig. 3 (women). As expected, rates of bother were lower for LUTS classified as at least ‘sometimes’ than those classified as at least ‘often’ (data not shown). Likewise, the proportion of those bothered ‘quite a bit’ or more was lower in the at least ‘sometimes’ classification than in the at least ‘often’ group.
Most LUTS were described as at least ‘somewhat’ bothersome by at least half of the participants who experienced them. Overall, similar proportions of men and women described symptoms as at least ‘somewhat’ bothersome, with slightly higher percentages of bother evident among women on storage symptoms, particularly those related to incontinence. Some of the least prevalent symptoms were among those most commonly reported as bothersome, such as leaking urine during sexual activity, which was most frequently reported as bothersome by both men (82.1%) and women (87.2%). Other storage symptoms associated with incontinence that were at least ‘somewhat’ bothersome among men included urgency with fear of leaking (73.3%), leaking for no reason (72.1%), nocturnal enuresis (71.5%), urgency incontinence (63.8%), and stress incontinence associated with physical activities (62.1%). Bladder pain (67.5%), straining (66.7%), dysuria (65.4%), urgency (59.0%), and incomplete emptying (54.4%) also were frequently reported to be at least ‘somewhat’ bothersome.
A similar pattern was evident among women, with incontinence symptoms frequently receiving at least ‘somewhat’ bothersome endorsements (leaking for no reason 84.7%; nocturnal enuresis 84.0%; urgency with fear of leaking 74.7%; stress incontinence associated with physical activities 74%; urgency incontinence 71.3%) followed by dysuria (73.5%) and bladder pain (69.3%). Terminal dribble, the most prevalent LUTS among both men and women, had relatively low rates of bother (men 40.6%; women 40.2%). With the exception of a few LUTS, the correlations between frequency and bother for men and women were moderate to strong, with r-values of >0.45 (range 0.45–0.74; data not shown), indicating a strong relationship between LUTS frequency and bother.
The prevalence of all LUTS increased with advancing age in men, but only certain LUTS increased with age in women (urgency, urgency with fear of leaking, weak stream, urgency incontinence, and nocturnal enuresis). When examining prevalence by country, rates of LUTS for both men and women were generally highest in the USA, followed by the UK and Sweden. In terms of bother ratings associated with LUTS, the Swedish participants generally reported the highest rates of bother for all LUTS, whereas the UK participants consistently reported the lowest.
To benchmark these data among other epidemiological studies, the IPSS grouped by severity score, i.e. none, mild (1–7), moderate (8–19), and severe (≥20) was used (Table 3) [3,13,15]. Importantly, the IPSS sum scores found in this sample are similar to those found in previous epidemiological studies using a self-administered IPSS.
Table 3. The IPSS results compared with previous reports
To our knowledge, EpiLUTS is the first epidemiological study using the current ICS definitions of LUTS conducted in the USA, the UK and Sweden. Irwin et al. used ICS definitions when evaluating the prevalence of OAB and some LUTS, but did not examine all LUTS and did not assess the acceptability of laymen’s language as applied to these definitions . The rigorous efforts in this survey development established the content validity of the questionnaire and ensured that lay people understood the questions being asked. The Internet-based data collection used here was a departure from the standard of random digit telephone dialling to collect epidemiological data, and provided a rapid, efficient venue of data collection that allowed participants to complete the survey when convenient to them. Using Internet-based self-administered data collection also negates the possibility of interviewer-bias and allows for a greater number of relevant questions to be asked. In EpiLUTS, the number of questions asked ranged from 123 to 185, with a mean completion time of 22 min.
Importantly, although Internet-based studies are a promising method for conducting large-scale epidemiological studies, the concern of general applicability and whether this Internet-based sample population is representative of the general population must be addressed. Critical to the success of EpiLUTS was ensuring population representativeness by maximizing population coverage and minimizing selection bias using sample-matching techniques. The sampling in EpiLUTS is based on each country’s current population census, focusing on the demographics of age, gender, race and education. Members of the pool of Internet-based panel participants were matched to the census demographics and randomly selected to receive the e-mail invitation to participate. Although the concern that Internet users tend to be over-represented by the higher educated, younger, majority population is valid, this survey method targeted a lower educated, older, minority population to match the population census demographics of each country. In the USA, minorities comprised 24% of the sample (nearly 10% in the UK), and 43% of men and 54% of women had a high-school education or less. Given the current trends of telephone use with caller identification and cellular phones, this Internet-based approached with sample matching is likely to have greater general applicability than random-digit dialling.
Because the method of epidemiological research for EpiLUTS differs from previous studies, the prevalence rates of individual LUTS noted in EpiLUTS were considerably higher when using the at least ‘sometimes’ threshold than previously noted [3,11,13], whereas the at least ‘often’ threshold yielded lower prevalence rates. Also, the prevalence rates of LUTS in the UK were higher than the Swedish rates, whereas the inverse was previously reported . There are likely to be various factors to explain the differences in prevalence rates, with the first being the recognition that how a question is asked will alter the response. Previous epidemiological studies used various surveys and questionnaires (e.g. IPSS, ICS-male, Danish Prostatic Symptom Score) to assess the prevalence of LUTS, and each questionnaire asks about LUTS in different ways. Respondent interpretation of each question might result in widely varied responses. The translation in different languages and the interpretation of the individual questions might result in the varied responses and differences in prevalence among these countries. Also, when considering the responses presented to individuals, a dichotomous yes/no response will yield a very different result from a Likert scale of four to six potential response options. Notably, for most questions in EpiLUTS, five-point Likert scales were used to allow respondents the opportunity to provide a real-life response of ‘sometimes’ when responding to the presence of a symptom. For example, when examining urgency, a symptom that is indicative of OAB, the ‘at least sometimes’ threshold prevalence rate of urgency is 22.4% for men and 35.7% for women, which is higher than previously reported by Irwin et al.. However, when the at least ‘often’ threshold is used, the prevalence of urgency is 4.9% in men and 11.1% in women, which is much lower than previously reported by Irwin et al.
Although the way the questions were asked and the response option formats probably explain much of the difference in noted prevalence rates, the lack of an interviewer-response bias might also contribute to noted differences. The inclusion of the IPSS as a benchmark assessment of LUTS shows that similar rates were found when comparing self-administered versions of the IPSS (albeit written vs computerized). The IPSS rates from EpiLUTS were quite similar to those noted by Anderson et al., Boyle et al. and Seim et al., with the prevalence being 28.3% of men with moderate to severe IPSS indicative of BPH.
It is important to acknowledge that although LUTS prevalence rates vary according to the chosen threshold, LUTS are highly prevalent in men and women aged ≥40 years. Voiding symptoms that are frequently associated with BOO and BPH in men were highly prevalent in women, while storage symptoms were prevalent in men. Importantly, LUTS are bothersome to those individuals experiencing them. In EpiLUTS, the level of bother was assessed with each LUTS, and the prevalence was reported as ‘rarely’ or more. Consistent with previous research, the most prevalent symptoms were not the most bothersome; in fact, the least prevalent symptom of incontinence during sexual activity was the most bothersome symptom for both men and women. Terminal dribble, the most prevalent LUTS, was among the least bothersome.
Further examination of the present data will provide greater insight into the level of bother and associated treatment-seeking behaviour for individual LUTS, as well as LUTS constellations among this population. For example, EpiLUTS data can provide an insight into what symptom or symptoms have the greatest adverse effect on people’s lives. Such information might be useful to clinicians and researchers in identifying levels of specific symptoms that lead to treatment-seeking. Is there a symptom ‘tipping point’ at which one can no longer tolerate coping with specific LUTS? Do specific symptoms trigger treatment seeking? While this study shows that LUTS are highly prevalent, there is a need for further longitudinal research to evaluate when symptom presence merits examination and treatment. Certainly, the mere presence of a symptom does not mandate either, but little is known about the natural progression of LUTS, and whether early identification and treatment will reduce future morbidity.
Additional analyses within EpiLUTS should help clinicians to gain an understanding and awareness of the trend between the highly prevalent and bothersome symptoms, and patterns of patient presentation, including association with comorbid conditions, with important implications for clinical management. Future research is needed to ascertain the clinical relevance, if any, of LUTS presenting individually or as a constellation of symptoms. Furthering cluster-analyses approaches [38,39] to examine not only the presentation of LUTS but risk factors and comorbid conditions associated with symptom constellations will enhance clinicians’ understanding of LUTS presentation from a patient’s perspective rather than an ‘organ’ (i.e. bladder or prostate) perspective . Lastly, from a clinical perspective, future longitudinal research is needed to see if there is a development of these symptoms into a perceivable and bothersome condition, to gain an understanding of the importance of early diagnosis and management of LUTS.
Additional editorial support was provided by Diane Warner and Janet E. Matsuura, PhD, at Complete Healthcare Communications, Inc., and was funded by Pfizer Inc. This research was supported by funding from Pfizer Inc.
CONFLICT OF INTEREST
Karin S. Coyne, Chris C. Sexton and Christine L . Thompson are employees of UBC and consultants to Pfizer Inc; Zoe S. Kopp and Lalitha P. Aiyer are employees of Pfizer Inc; Christopher R. Chapple is a Scientific consultant/researcher with Allergan, Astellas, Novartis and Pfizer Inc; Steven Kaplan is a consultant/lecturer with Pfizer Inc; Andrea Tubaro is a consultant for Allergan, Astellas, Ferring, GSK Novartis and Pfizer Inc; Alan J. Wein is a consultant to Allergan, Astellas, Novartis and Pfizer Inc; Ian Milsom is a consultant to Pfizer Inc and UBC, an investigator for Pfizer Inc and Astellas, a lecturer for Pfizer Inc, Astellas and Novartis, and receives grant support from Pfizer Inc and Astellas; Debra Irwin is a consultant for Pfizer Inc.