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The Norwegian EPINCONT Study: Epidemiology of Urinary Incontinence in Nord-Trøndelag

The Nord-Trøndelag Health Survey 1995-97

The Nord-Trøndelag Health Survey 2 (HUNT 2) was a large survey performed in one county in Norway during the years 1995-97. This county has a geographical, demographical and occupational structure fairly representative of Norway as a whole, although the average income and the prevalence of higher education is somewhat less than the average for Norway. Considering the number of participants and the extent of information collected , this is the largest medical survey ever performed in Norway. Everyone aged 20 years or more (N=94197) residing in the county were invited to participate. The complete HUNT 2 survey covered many topics, for example mental health, cardiovascular diseases, diabetes, asthma, osteoporosis, musculo-skeletal sufferings , hearing and vision, metabolic diseases, iron-metabolism, reproductive health and urinary incontinence. A similar survey was performed in the same county during the years 1984-86 (HUNT 1).

Invitations were sent by mail along with Questionnaire 1, which was to be returned when attending at the screening-station. This was a stationary or mobile (bus) office in each municipality. Questionnaire 1 did not contain any questions about urinary incontinence. Blood-pressure, pulse, height, weight, hip- and abdominal width and a set of blood-tests were taken for everybody and further investigations were performed for smaller samples of the participants. Before leaving the screening-station all the participants received Questionnaire 2 (different for men and women), which was to be filled in at home and returned by mail. Questions about urinary leakage were included among approximately 130 questions asked to women.

47313 women were invited to the HUNT 2 study. 948 women were institutionalized, but only 60 of these participated in the study. The overall participation rate in HUNT 2 was 74%, lowest in the youngest and the oldest age groups. 34755 community-dwelling women received questionnaire 2. These are defined as the source population of the EPINCONT study; institutionalized women were excluded. 27936 women (the study population) answered the questions about urinary incontinence, giving an overall response rate for the EPINCONT study of 80%. The data-collection was concluded in 1997. Our group is one of ca 30 groups of researchers who started analysing the data during 1998.

Questionnaire for urinary incontinence
Our questionnaire on urinary incontinence consisted of eight questions. The participants were first asked if they had involuntary loss of urine. If the answer was positive further questions were posed to reveal the frequency and severity of urine loss, type of incontinence, the duration of the condition, whether a doctor has been consulted on this matter, and to what extent the UI is experienced as a problem. More specifically, after the entry question, the questions covered:

Urinary incontinence was defined as any leakage. A severity index developed by Sandvik et al. was used to characterize the degree of incontinence. The index was calculated by multiplying the reported frequency (four levels) by the amount of leakage (dichotomized to two levels). The resulting index value (1-8) was further categorized into slight (1-2), moderate (3-4) and severe (6-8). Typically, slight incontinence denotes leakage of drops a few times a month, moderate incontinence daily leakage of drops, and severe incontinence larger amounts at least once a week. The severity index has been validated against a 48 hour "pad weighing" test. According to this test, slight incontinence means a leakage of 6 g/24 hours (95% CI 2-9), moderate incontinence means a leakage of 17 g/24 hours (95% CI 13-22) and severe incontinence means a leakage of 56 g/24 hours (95% CI 44-67). The severity index is thus a semi-objective and quantitative measure, and does not include the woman`s subjective perception of her leakage as being a problem or not. Based on descriptions of typical situations of leakage, the incontinence was classified into stress, urge, mixed and (other( urinary incontinence.

Other variables and risk factors for UI
In addition, we have access to the other several hundreds of variables in the survey, giving us the opportunity to find possible risk factors for UI and co-existing conditions. In addition to the other main topics mentioned above, the survey includes data on menstruation and menopause, number of pregnancies and births, gynaecological operations, the use of estrogens and other medication, smoking and other lifestyle-factors.

Medical Birth Registry of Norway,- evaluation of parturition as risk factor for UI
The Medical Birth Registry of Norway has since 1967 registered every birth in Norway with variables describing the mother (age, marital status, parity, health before and during pregnancy), the child (gestational age, length, weight, head circumference, Apgar score) and the birth (complications, cesarean sections and other interventions). The use of the National identity number in both the registry and the Nord-Trøndelag Health Survey enable us to link the two data sets and analyse the relationship between childbearing and UI.

Ethics and data security
Ethical approval for HUNT was obtained from both the Regional and the National ethics review board. The subjects gave an extensive written consent to the use of the data. HUNT has also obtained approval from the Norwegian Data Inspectorate.

Published studies

1. Hannestad Y, Rortveit G, Sandvik H, Hunskaar S. A community-based epidemiological survey of female urinary incontinence. The Norwegian EPINCONT study. J Clin Epidemiol 2000;53:1150-7

In this substudy we report the crude prevalence rates and emphasize analyses on age, severity and type of incontinence. 25% of the participating women had urinary leakage. Nearly 7% had significant incontinence, defined as moderate or severe incontinence that was experienced as bothersome. The prevalence of incontinence increased with increasing age. Half of the incontinence was of stress type, 11% had urge and 36% mixed incontinence. Urge symptoms, and even more mixed incontinence, seem to be connected with an increasing degree of both severity and bother compared with pure stress incontinence symptoms. Severity increased with age regardless of type.

2. Rortveit G, Hannestad Y, Daltveit AK, Hunskaar S. Age- and type-dependent effects of parity on urinary incontinence. The Norwegian EPINCONT study. Obstet Gynecol 2001;98:1004-10.

The association between parity and urinary incontinence, including subtypes and severity of incontinence, was investigated. Prevalences among nulliparous women ranged from 8% to 32%, increasing with age. Parity was associated with incontinence, and the first delivery was the most significant. The association was strongest in the age group 20-34 years with RR 2.2 (95% confidence interval: 1.8,2.6) for primiparous and 3.3 (2.4,4.4) for grand multiparous women. A weaker association was found in the age group 35-64 years (RRs between 1.4 and 2.0), while no association was found among women over 65 years. For stress incontinence in the age group 20-34 years the RR was 2.7 (2.0,3.5) for primiparous and 4.0 (2.5,6.4) for grand multiparous women. There was an association with parity also for mixed incontinence, but not for urge incontinence. Severity was not clinically significantly associated with parity.

3. Hannestad Y, Rortveit G, Hunskaar S. Help seeking and associated factors in female urinary incontinence.The Norwegian EPINCONT study. Scand J Prim Health Care 2002;20:102-7.

The aim of this study was to assess the proportion of women who had visited their doctor because of urinary leakage and to find factors independently associated with help seeking. 26% of the incontinent women had seen a doctor for their incontinence. Increasing age, impact, severity and duration were all significantly associated with consultation rate, as were urge and mixed types compared with stress incontinence, and having visited any doctor during the last twelve months. Fifty percent of the women with significant incontinence had seen a doctor because of their incontinence.

4. Hannestad, YS, Rortveit G, Daltveit AK, Hunskaar S . Are smoking and other lifestyle factors associated with female urinary incontinence? The Norwegian EPINCONT Study. BJOG 110(3): 247-54.

The aim of this study is to evaluate the role of smoking and other modifiable lifestyle factors potentially associated with urinary incontinence in women.

5. Rortveit G, Daltveit AK, Hannestad Y, Hunskar S. Urinary incontinence after vaginal delivery or cesarean section. N Engl J Med 2003; 348:900-7.

In this study we investigate whether cesarean section imposes a risk of incontinence, and whether vaginal delivery further increases the risk.

Ongoing studies:

1. Hannestad Y, Lie RT, Rortveit G, Hunskaar S. Is there a familial prevalence of urinary incontinence? The Norwegian EPINCONT study. Manuscript.

In this substudy we want to investigate whether the daughter or the sister of an incontinent woman is at higher risk for incontinence compared to women with continent first-degree relatives. By an encrypted coupling of the HUNT-data to the national identity number we obtain information on the kinship between the participating women.

2. Rortveit G, Daltveit AK, Hannestad Y, Hunskaar S. Delivery parameters as risk factors for urinary incontinence. The Norwegian EPINCONT study. Manuscript

In this study we investigate whether delivery parameters such as birth weight, gestational age, use of forceps etc. play a role in the development of urinary incontinence. Approximately 11500 women with only vaginal births are selected for this study.

Presentations of the EPINCONT study (with published abstracts)

  1. Hannestad Y, Rortveit G, Sandvik H, Hunskaar S. A community-based epidemiological survey of female urinary incontinence. The Norwegian EPINCONT study. Oral presentation. The 1st Nordic Conference in Epidemiology. Bergen, Norway, June 12-15, 2000. Nor Epidemiol 2000;10 (Suppl 2):
  2. Hannestad Y, Rortveit G, Hunskaar S. A community-based epidemiological survey of female urinary incontinence. The Norwegian EPINCONT study. Abstract, poster. International Continence Society 30th Annual Meeting Tampere Hall, Tampere, Finland August 28 - 31, 2000
  3. Rortveit G, Hannestad Y, Daltveit AK, Hunskaar S. Age- and type-dependent effects of parity on urinary incontinence. The Norwegian EPINCONT study. Oral presentation. The 9th Norwegian Conference in Epidemiology. Tromsø, Norway, November 22-23 2001. Norsk epidemiologi 2001;11(suppl.2):32.
  4. Hannestad Y, Rortveit G, Daltveit AK, Hunskaar S. Are smoking and other lifestyle factors associated with female urinary incontinence? The Norwegian EPINCONT study. Abstract, poster and oral presentation. ICS August 2002, Heidelberg
  5. Rortveit G, Daltveit AK, Hannestad Y, Hunskaar S. Can cesarean section prevent urinary incontinence? The Norwegian EPINCONT study. Abstract, poster. ICS August 2002, Heidelberg

Research group for Urinary Incontinence
At Division for General Practice, Department of Public Health and Primary Health Care, University of Bergen, Norway, we have established a research group consisting of several researchers.

The EPINCONT study:
Principal investigator: Steinar Hunskaar, MD, PhD, Professor in general practice (steinar.hunskar@isf.uib.no)

Co-investigators:

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Department of Public Health and Primary Health Care, last updated 25.03.03

Hogne.Sandvik@isf.uib.no