Lower urinary tract symptoms in patients with Niigata Minamata disease: A case-control study 50 years after methyl mercury pollution

Objectives To clarify the prevalence of lower urinary tract symptoms and overactive bladder in patients with chronic methyl mercury poisoning. Methods A total of 151 patients (61 men and 90 women; mean age 72.1 years) with Niigata Minamata disease were enrolled. An age- and sex-matched group of 150 participants was used as control. Patients reported their International Prostate Symptom Score and overactive bladder symptom score. Results In men, the total, storage and voiding International Prostate Symptom Score scores were higher in the Niigata Minamata disease group than in the control group (10.6 +/- 7.8 vs 5.0 +/- 5.0, 4.5 +/- 3.3 vs 2.4 +/- 2.4 and 6.1 +/- 5.1 vs 2.7 +/- 3.1, respectively, P<0.001 in all). In women, these scores were also higher in the Niigata Minamata disease group than in the control group (8.9 +/- 7.3 vs 4.0 +/- 4.0, 4.4 +/- 3.2 vs 2.8 +/- 2.4 and 4.5 +/- 5.0 vs 1.3 +/- 2.0, respectively, P<0.001 in all). The prevalence of overactive bladder was more frequent in the Niigata Minamata disease group compared with that in the control group (51.7% vs 26.7%, P<0.001). In both men and women, the overactive bladder symptom score was higher in the Niigata Minamata disease group than in the control group (4.1 +/- 3.0 vs 2.4 +/- 2.9, P=0.002 and 4.6 +/- 3.6 vs 2.7 +/- 2.9, P<0.001, respectively). The International Prostate Symptom Score and overactive bladder symptom score in the Niigata Minamata disease group were highest in patients aged 60-69 years (P<0.001 in both), whereas these increased in an age-dependent manner in the control group. Conclusions Lower urinary tract symptoms and overactive bladder are severe and highly prevalent conditions among patients with methyl mercury poisoning. The higher prevalence of lower urinary tract symptoms among patients aged 60-69 years might be related to the fact that they were exposed to methyl mercury during their childhood/development.