The present study assessed the impact of different levels of severity and types of urinary incontinence on the patient’s generic and condition-specific quality of life.
Some characteristics of our study population were also significantly related to the quality of life and (the most relevant) are described in the Results section. In summary: a higher age, higher BMI and more co-morbidity negatively influences the generic quality of life. The negative relation between SES and the condition-specific quality of life indicates the opposite, because the higher the SES the better the quality of life.
However, the most important outcome is that about half of the participants were troubled by mixed urinary incontinence (50.7%) and a moderate severity of urine loss (48.9%); this mixed urinary incontinence had a greater impact on the emotional domain of the condition-specific quality of life as compared to stress urinary incontinence, although there is no difference compared with urgency urinary incontinence.
Women with symptoms of stress urinary incontinence are less dependent on their urine loss because they tend to lose urine during situations which are generally known to them and thus might be avoided . However, the degree of severity of the incontinence influences both the generic and the condition-specific quality of life.
Compared to patients with slight urinary incontinence, patients with severe urinary incontinence (23%) experience more impact of urinary incontinence on all domains of the condition-specific quality of life, as well as on the condition-specific quality of life total score. Moreover, severe urinary incontinence also diminishes the generic quality of life compared to slight urinary incontinence, whilst there is no effect of moderate severity on quality of life as compared to slight severity of urine loss. Therefore, it appears that the severity of the symptoms, rather than the type of urinary incontinence, is a greater predictor for a decreased quality of life.
Comparison with existing literature
As mentioned above, mixed urinary incontinence is associated with lowered condition-specific quality of life as compared to stress urinary incontinence, as also reported by Schimf et al. , whereas there is no significant difference with regard to urgency urinary incontinence, as also reported by Frick et al. .
When increased, symptom severity (as measured by the IIQ-7) diminishes the condition-specific quality of life in general, as also found by Tennstedt et al.  and Huang et al. .
No differences were found between the types of urinary incontinence and their effect on the generic quality of life. This result is consistent with findings of Grimby et al.  and Coyne et al.  but in contrast to Botlero et al.  who argue that mixed urinary incontinence is associated with a larger reduction in overall wellbeing. However, in the latter study mixed urinary incontinence had more impact on emotional wellbeing and mood, which in our study is described as the emotional domain of the condition-specific quality of life. Differences in the choice of measurements and interpretation might be the reasons for the differences found between these studies.
Strengths and limitations
In this population-based study, women were included on the basis of randomizing their GP. However, because these women are a random selection (based on age ≥ 55 years), at the time of screening it is unknown whether they have already asked for help, either recently or in the past.
In the primary care setting these women with urinary incontinence have rarely been studied.
In the present study, different types of urinary incontinence as well as the severity of its symptoms and effects on quality of life were explored, whereas other studies mainly investigated either the type or the severity of urinary incontinence.
Also, this study uses both generic and condition-specific questionnaires, which is recommended by Dugan et al.  and Naughton et al. ; the latter in particular report that the IIQ and EQ-5D are highly recommended. The use of both questionnaires allows to assess symptom distress as well as general wellbeing.
Self-administered questionnaires (allowing a person to judge their own health status) are important for the present study. However, self-reports on the type of urinary incontinence and severity of symptoms can lead to a potential bias in data because of subjective symptom perception .
Another potential limitation of this study is the inclusion of women who participated because they already have symptoms, thus precluding comparison with women without urinary incontinence. Also, women suffering from urinary incontinence may already experience a somewhat diminished quality of life.
The willingness to participate was 48%, which was more than expected at the start of the trial. However, any loss is a limitation and in this study the main reasons for non-response were: too great a burden to participate (19.7%), not wishing to undergo more examinations/research in this or other areas (17.4%), and being too old (15.5%, with a mean age of 72 years).
Also, because this study has a cross-sectional design with only one measuring point, the direction of the causal relationship between urinary incontinence and (factors of) quality of life cannot be determined, as this association could also be bidirectional.
Finally, because this study included only women in the Netherlands aged ≥ 55 years, these results cannot be extrapolated to other cultures and are not generalizable to all ages.
Implications for future research
The use of different types of measurements can provide valuable information for future research. However, we need to establish which measuring instrument is most effective to study the relation between urinary incontinence and quality of life, or whether the use of two or more questionnaires may be a better approach to obtain maximum insight on this topic [11, 13].
We recommend to perform a longitudinal study, with several measuring points, to assess whether changes in symptoms are related to changes in quality of life. Performing a population-based study will allow comparisons to be made between patients with and without urinary incontinence, and to establish differences in generic quality of life due to the impact of urinary incontinence.
More research is required on differences between the types urinary incontinence and their effect on quality of life, especially with regard to urgency urinary incontinence.
In addition, the level of burdensomeness may differ between age groups because some symptoms and complaints are often assumed (like co-morbidity) to ‘belong’ to older age. Studying younger women with urinary incontinence (albeit a smaller group) may increase our knowledge on the impact of urinary incontinence on the quality of life.
Finally, due to the aging of society and knowing that urinary incontinence increases with age, early detection and treatment is an important part of future care and other considerations related to rising costs.