The prevalence of falls increases with age, and the risk of falling is higher in women than men. In addition complications such as fractures due to falls can evoke severe morbidity or mortality in the old and post-menopausal. Risk factors for falls are old age, female gender, visual disturbance, cognitive disorder, use of tranquilizers, etc. Voiding difficulties including incontinence are also known risk factors [5
OAB, which is one of the causes of incontinence, is defined as a condition of urgency with or without urge incontinence, usually with frequency and nocturia. OAB reduces the quality of life of affected persons, an aspect that has received attention only recently [12
]. Voiding symptoms of OAB include urgency, urge incontinence, frequency and nocturia. The changes of behavior induced by these voiding symptoms are considered to affect the likelihood of falls, and this idea is supported by several studies showing that incontinence is a risk factor for falls [4
]. However those studies did not discriminate between urge and stress incontinence, and used questionnaire that had not been validated. Therefore they have limitations with regard to supporting the correlation of OAB with falls.
KHQ is a voiding questionnaire that can assess the severity and effect on quality of life of voiding symptoms; it is of proven validity and reproducibility in assessing incontinence and OAB [14
]. In addition, the Falls Efficacy Scale (FES) was designed to assess the degree of perceived efficacy in avoiding a fall during relatively non-hazardous daily activities [16
]. However, because the questions are restricted to basic and instrumental activities of daily living, the answers do not reflect individual differences, and the sensitivity of the questionnaire in detecting loss of confidence in maintaining balance in elderly persons capable of functioning in daily life is low [17
To avoid this weakness, Powell and Myers [18
] designed an activities-specific balance confidence (ABC) scale. The greater item-responsiveness of the ABC scale makes it more suitable for detecting loss of balancing confidence in more highly functioning seniors [19
]. Yardley et al. [20
] designed the Falls Efficacy Scale-International (FES-I), which combines the advantages of FES in assessing indoor activity and the advantage of ABC in measuring outdoor activity. FES-I has greater validity and reliability than the FES in assessing fear of falling. Also the reliability of KFES-I for measuring the risk of falling has been supported by examination of its internal consistency and the test-retest method [21
In our study, we found that 27.5% of females aged 40 or over who answered 'moderately' or 'a lot' with regard to urgency or urge incontinence in the KHQ, had experienced falls, and OAB increased the risk of falls 1.76 fold compared to the group without OAB. The falls due to OAB may be explained in several ways. Sufferers may hurry to the toilet to avoid social embarrassment due to urge incontinence, or their increased frequency of urination, or nocturia, may disrupt their sleeping pattern, diminish daytime wakefulness and lead to visual disturbance at night [22
Interestingly, the frequencies of underlying diseases that are known risk factors for falls such as diabetes, cerebro/cardio vascular disease and osteoarthritis did not differ between our two groups. Also general expectations of falls was not associated with other medical condition. This finding may have been due to a selection bias that excluded females who could not visit the public health center where they lived due to gait disturbance caused by medical or neurologic disorders or severe osteoarthritis.
In previous studies, although the correlation between treatment of OAB and reduction of risk of falls was not established, the necessity of treatment of OAB to reduce the risk of falls was mentioned [8
]. Treatment of OAB may reduce the risk of falls because the behavioral changes resulting from OAB increase the risk of falls.
In our study, age, presence of partner, educational status, hypertension, cerebro/cardio vascular disease and osteoarthritis, were associated with OAB, but domicile, diabetes and osteoporosis were not. The lack of effect of domicile implies that socioeconomic status and mode of life have insignificant effects on OAB compared to underlying disease; it follows that consideration of underlying disease should take priority over consideration of socioeconomic status in the screening and diagnosis of OAB, and in the prevention and treatment of falls due to OAB.
The group with OAB contained 1.5 times more persons lacking partners than the group without OAB, and showed a tendency towards lower educational status, but these two effects were not statistically significant. These results suggest that partners and preventive education are ineffective in preventing falls. Hence more understanding, assistance and multifarious preventive educational measures may be needed to prevent falls.
Fear of falling is defined as a psychological state of anxiety of falling in elderly people who have experienced falls. It restricts the activities of the elderly and induces body weakness, and the risk of falling increases with body weakness [25
]. In the present study, the proportion of those in the group with OAB with high fear of falling was 37.9%, 2.7 fold higher than in the group without OAB. This implies that experience of falls due to urgency or urge incontinence induces fear of falling. In other words, OAB as a disease entity affects not only voiding symptoms but also individual physical and psychological status, and so can affect an individual's entire quality of life. Furthermore, a substantial increase of direct costs can be anticipated due to the increase in the aging population [26
] and the overall prevalence of lower urinary tract symptoms including OAB has not changed in the last several years [27
]. This means that we should change our conception of OAB from a disease restricted to individuals' voiding symptoms to a social health problem in need of prevention and treatment.
This study has some limitations. It did not use common definition of OAB. In this study, OAB was defined as an answer of 'moderately' or 'a lot' of urgency, or urge incontinence in KHQ to promote convenience of survey in large scaled cohort study and prevent misunderstanding about OAB in the olds and illiterates. It did not assess the correlation between treatment of OAB and decreased risk of falls, which is the context of OAB and falls, or, due to a selection bias, the correlation between underlying disease and falls.
On the other hand, the study had some strengths. It revealed correlations of OAB with falls and fear of falling, and between severity of urgency or urge incontinence and falls and fear of falling, by using the KHQ and KFES-I questionnaires whose validity and reliability have been established. Moreover the outcomes can be generalized because the responders were part of the general population living in urban and rural areas. Moreover, the data are trustworthy because they were collected with the help of a well-trained assistant.
Early treatment and preventive education may be needed to reduce the risk of falls and to improve the quality of life of women suffering from OAB. In future, to identify the correlation between falls and other risk factors, more aggressive methods of data collection such as telephone surveys or home visits may be needed to reduce selection bias due to gait disturbance. A large-scale multicenter prospective study should be performed to assess the effect of treatment of OAB on the prevalence of falls and quality of life.
In conclusion, independent of age, educational status, dwelling place, presence of partner and underlying disease, OAB increases the risk of falls 1.8 fold, and of high fear of falling 2.7 fold, in women aged 40 or older in the community.
Early diagnosis and treatment of OAB, more understanding, assistance by partners and preventive education, may be needed to improve the quality of life and decrease the risk of falls. A large-scale multicenter prospective study should be performed to examine the effect of treatment of OAB on the prevalence of falls and quality of life.