MS with focal demyelinating lesions at different levels of the central nervous system (CNS) leads to urinary dysfunction.[23] In the present study, the prevalence of LUTS was high among patients with MS (reaching to more than ¾ of the patients), and 41.3% of patients had moderate to severe urinary symptoms. This finding was similar to the findings of the study by Nakipoglu with an 80.81% prevalence of LUTS and the study by Sammarco with 43% moderate to severe bladder dysfunction among patients with MS.[13,24] The different estimates reported for the prevalence of LUTS in MS range between 32% and 97%,[25,26] and the high prevalence of LUTS suggests the complexity of neural control of the function of the bladder and urinary tract and the location and nature of the neural lesions determines the pattern of bladder dysfunction.[27]
In the present study, more than half of the patients with MS had mixed urinary tract symptoms and the incidence of storage or irritative symptoms was higher in comparison to urination or obstructive symptoms. In the study carried out by Onal et al., the prevalence rate of mixed symptoms among patients with MS (70%) was higher than the irritative (25%) and obstructive symptoms (5%) alone.[36] In addition, in the cross-sectional study by Ojewola et al., storage or irritative symptoms with an prevalence rate of 48.2% were more common than urination and post-urination symptoms with rates of 36.8% and 29.9%, respectively, in patients with MS.[29] Reports from western countries have indicated that irritative symptoms (storage phase) are prominent symptoms of the urinary tract, while in eastern countries, the prevalence of obstructive symptoms (voiding phase) is higher than irritative symptoms.[30]
In addition, in this study, more than half of the men and women reported mixed symptoms, and the prevalence rate of irritative symptoms among women alone and obstructive symptoms among men alone was higher and the difference was statistically significant. In this regard, the study by Sand et al. also indicated that 60% of men and 50% of women with MS had reported mixed symptoms;[18] however, the results of the study by Aharony indicated that there was no significant correlation between the overall incidence of LUTS and gender.[31] The results of an investigation on 8284 men and women in China, Taiwan, and South Korea revealed that the prevalence of storage symptoms alone was higher among women compared to men (23.8% versus 12.6%, respectively) and obstructive symptoms alone had a rate of 7.2%.[32] However, due to the widespread nature of the lesions of the nervous system among patients with MS, numerous levels of control of the function of the bladder and intestine are observed,[8] and the nature of urination complaints and LUTS varies among patients with MS.[26] In addition, LUTS change over time along with the dynamic course of MS. Therefore, continuous and regular follow-up assessment is required in patients with MS. [27]
In the current study, the prevalence of mixed urinary symptoms in patients over 30 years of age (55.1%) was higher than the age group of below 30 years (46%), and the difference was statistically significant. The results of a study showed a high prevalence rate for LUTS among men and women with a minimum age of 40 years and a significant increase in LUTS with age in the general population (at the age of 40-44 years to over 60 years with a prevalence of 49.9% and 69.7%, respectively).[32] Based on a cross-sectional population-based study, there was a relationship between LUTS and age among women, but not among men, as younger men had a lower prevalence of LUTS in comparison to younger women, and older men had higher LUTS prevalence rate in comparison to older women.[33] Moreover, another study, a significant positive correlation was found between age and LUTS.[34]
In the current study, the prevalence of LUTS among patients with an education level of below diploma was higher than those with diploma and university degrees, and the difference was statistically significant. In this regard, the results of a cross-sectional study based on population in Australia did not show a significant positive correlation between LUTS and educational status. [34]
The present study showed that the prevalence of irritative LUTS was higher in patients with MS with mild disability (EDSS ≤ 3). Nevertheless, the prevalence of mixed LUTS among patients with severe disability (EDSS ≥ 7) was higher than patients with mild to moderate disability and the difference was statistically significant. In the study by Di Filippo, 44% of patients with mild EDSS reported bladder dysfunction and this rate was increased among patients with moderate and severe disability (81%) and EDSS and the severity of corticospinal pathways had a significant correlation with the prevalence of irritative symptoms. [35] In addition, another study revealed that there was relationship between a high degree of disability and high levels of LUTS. [36]
Khalaf et al. found that patients with MS with higher degree of disability had higher irritative symptoms (urgency and UI),[38] and the findings of the study by Onal revealed a weak correlation between EDSS severity and storage, urination, and total scores.[28] Arhrony found that irritative (storage) symptoms are associated with EDSS and the involvement of pyramidal pathways, but this association is very weak with obstructive symptoms.[31] In some other studies, there was a direct correlation between the EDSS score and irritative or obstructive symptom score,[38,39] albeit no relationship was reported between these variables in the studies by Miller and Porru.[40,41] It seems that the differences in the results of different studies are due to the clinical course of MS which the patients under study were undertaking during the study period. De Carvalho showed that in patients with neuromyelitis optica spectrum disorder (NMO-SD), the severity of disability was a predictor of bladder dysfunction and detrusor-external sphincter dyssynergia (DESD). [42]
The present study indicated that the prevalence of irritative LUTS was higher among patients with MS and disease duration of less than 5 years, but the prevalence of mixed LUTS in patients with MS and disease duration of more than 10 years was higher compared to patients with MS and disease duration of less than 5 years and between 5-10 years, and the difference was statistically significant. The results of a study in Brazil showed a weak significant relationship between the duration of the disease and the presence of urinary dysfunction, and the degree of urinary dysfunction increased over the years.[43] In another study, the duration of disease and higher degree of disability only had a significant relationship with higher levels of urinary symptoms in women.[13] The review of data from the American Research Committee on Multiple Sclerosis (NARCOMS) showed that, with an increase in the duration of disease, the severity and prevalence of LUTS increased, so that on average 35-39% of patients 5-6 years after the onset of the disease, and in contrast, 64% of patients with a 17.1 year history of disease reported LUTS.[44]
The current study revealed that the prevalence of LUTS was higher in patients with CIS; however, the prevalence of mixed LUTS in patients with progressive MS was higher in comparison to patients with MS with RRMS and CIS, and the difference was statistically significant. De Almedia reported prevalence rates of 63.5% and 100%, respectively, among patients with RRMS and primary progressive MS. [43] Moreover, a study by Wang et al. showed the lowest OBASS score in patients with CIS. [23]
In the present study, patients with MS and LUTS symptoms compared to LUTS-free patients had lower QOL scores in all dimensions except for health changes and there was a significant difference in the combined physical and mental health dimensions of QOL between the two groups with and without LUTS. In addition, there was a higher possibility of a urinary tract complication in patients with MS with a higher EDSS score. These results were basically similar to the results of a population-based cross-sectional study in Korea performed on 658 individuals; nearly a quarter (25.5%) of the population with LUTS had lower QOL scores.[36] In this regard, Wang found that the higher the EDSS score, the higher the possibility of LUTS.[31] Furthermore, the study by Khalaf et al. suggested that patients with MS with immediate urgency and UI had significantly lower QOL in comparison to patients with MS without these symptoms.[45]
The strengths of this study included the appropriate sample volume and suitable ratio of men to women based on the proportion of MS prevalence rate in society. Considering the fact that the research was based on patients’ own statements on LUTS, the memory capacity of the subjects to recall their past information was one of the limitations in this study. Moreover, mind obsessions and everyday issues and factors such as fatigue, economic and family issues, or the presence of the inquirer when completing the questionnaire could affect the way in which the participants responded to the questionnaire.