Incidence of nocturia in 50 to 80-year-old Finnish men

Purpose: We estimated the incidence and natural course of nocturia in an unselected Finnish male population. Materials and Methods: A mail interview of a cohort of 3,143 randomly selected men 50 to 70 year old at study entry was done in Finland in 1994, 1999 and 2004. The questionnaire included questions on sociodemographic status, overall health and disease, urinary symptoms, sexual functioning and symptom bother. The overall response rate was 70% on the 1994 survey, 75% on the 1999 survey and 76% on the 2004 survey. A response to nocturia questions was obtained from 1,633 men at the 1994 to 1999 followup and from 1,618 at the 1999 to 2004 followup. Results: The overall prevalence of 1 or more nocturnal voidings was 56% at baseline and 74% 10 years later. The crude incidence rate for nocturia was 75 new cases per 1,000 men annually (95% CI 66 to 85) during the first 5-year followup period and 126/1,000 (95% Cl 113 to 140) during the second period. The incidence of moderate or severe nocturia was 9/1,000 (95% CI 7 to 11) and 14/1,000 men (95% CI 12 to 17), respectively. Incidence and prevalence increased clearly with age but also by calendar time, which was most prominent for the mild nocturia incidence. The incidence of moderate to severe symptoms increased, especially in the oldest cohort (incidence density ratio 5.6 to 5.7/5 years). Conclusions: Every year 10% more males older than 50 years start to void during the night. The incidence of mild nocturia increases, especially in men when they age from 50 to 60 years. In older men mild symptoms are more stable but the incidence of severe nocturia increases strongly after age 75 years.