The Nord-Trøndelag Health Survey 2 (HUNT 2) was a cross-sectional survey conducted in the county of Nord-Trøndelag, Norway, in 1995-97. It was a follow-up study of a similar survey, HUNT 1, conducted in 1984-86. Nord-Trøndelag is well suited for surveys like this since its geography, demography and inhabitants are fairly representative for Norway. Nord-Trøndelag, however, has no big cities, and its inhabitants have an income and educational level slightly below average.
All the inhabitants aged 20 years or older in the county were invited to participate (n = 94 197), 47 313 were women. The invitations mailed to the inhabitants included questionnaire 1 (Q1), which was answered by 34 755 women. The participants were asked to bring the completed questionnaire to a screening station, where among other measurements blood pressure, height and weight were measured, and blood samples were drawn. The women who met at the screening station received questionnaire 2 (Q2), which was different from men, and which among other topics contained questions on UI.
The incontinence part of the questionnaire is known as the EPINCONT study (Epidemiology of incontinence in the county of Nord-Trøndelag) [9]. Urinary incontinence was defined in accordance with the standards of the International Continence Society as "any leakage of urine" [10]. Type of incontinence was determined by asking the women about the situations in which they experienced leakage. If leakage occurred in association with lifting heavy items, laughing, coughing or sneezing the women were categorised as having symptoms of stress UI. Leakage in association with a strong urge to void was categorised as urge UI. The incontinent women who had both stress and urge symptoms were classified as having mixed type incontinence. For a small number of women (19) type could not be determined due to incomplete answers [9]. The women further answered questions about frequency of leakage (four levels), and amount of leakage (three levels), which were used to determine Sandvik's severity index [11]
Q1 also had a question on diabetes status, and those answering affirmative to the question "Do you have or have you had diabetes?" received questionnaire 3 (Q3) containing further questions on their diabetes situation [12]. This questionnaire contained questions on subjects like diagnosis, treatment (insulin, tablets, none), monitoring of the diabetes (home monitoring, monitored by health personal), diet, membership in Norwegian Diabetes Association, vision issues, hospitalization since diagnosis, quality of life and foot problems. The participants identified as having diabetes had an additional 5 ml EDTA blood drawn for HbA1c analysis. They also received three urine tubes for overnight urine sampling, which were analysed for microalbuminuria and creatinine to calculate the albumine:creatinine ratio (ACR). Women who through Q1 were identified as having diabetes were given new appointments for fasting serum sample, used for analyses of glucose, C-peptide and anti-GAD. Anti-GAD was analysed via immunoprecipitation, using (3H)leucine translation-labelled GAD65 as an indicator. The women were cathegorized as having type II DM if concentration of anti-GAD was below 0.08. Further information about methods and instruments used for blood-sample analyses are described elsewhere [12].
Response rate was high, 80% (27 936) of the women meeting at the screening stations answered the incontinence part of the study, and out of these 75% answered the questions on diabetes. This provided us with data on a total of 685 women with diabetes.
Statistics
Data were analysed using SPSS (version 15.0). Statistical significance was accepted at a 5% level (p < 0.05). We used Chi-Squared Test to test for differences in prevalence of diabetes type, non fasting glucose, HbA1c, duration of diabetes, diabetes treatment, cholesterol value, triglyceride value, albumine: creatinine ratio, oestrogene use, angina, heart attack, stroke or cerebral hemorrhage, hospitalization during the last 12 months and homecare between women with and without UI. Logistic regression analyses were performed to investigate the association between diabetes-related factors and UI among the women with diabetes. In a previous study we found that age, BMI, parity and smoking confounded the association between diabetes and UI, and these factors were therefore adjusted for in the final logistic regression analyses also in the current study [5]. Analyses were performed separately for each of the different outcomes under investigation, continent women serving as reference group in all the analyses. Parity and smoking were categorical variables, and no children and never smoked were used as alternative outcomes. Age and BMI were used as continuous variables. Odds ratios with corresponding 95% confidence intervals (CI) were effect measures. Duration of diabetes was used as a continuous variable. We chose to use the following variables as categorical, with the following alternative outcomes: blood glucose < 11.1 mmol/l, HbA1c ≤ 7.0 mmol/l, ACR < 2.5 mg/mmol, cholesterol < 7.7, triglyceride ≤ 2.45, diet treatment, no hospitalization during the last 12 months, no homecare, no angina, no stroke and no heart attack.
The women with diabetes categorized into a different type than type 1 DM and type 2 DM, and those not possible to categorize due to incomplete data, were added together into the group "other type of DM" for our analyses in figure 1.
Ethics
The main study had ethical recommendation from both the Regional and National Ethics Review Boards. Attendance was completely voluntary and the subjects gave an extensive written consent to the use of the collected material. The survey was also approved by the Norwegian Data Inspectorate.
