title: Time-series analysis of monthly age-specific numbers of newly registered cases of active tuberculosis in Japan from 1998 to 2013.
abstract: We investigated the seasonality of age-specific tuberculosis (TB) in Japan. To allow the development of TB control strategies for different age groups we used a time-series analysis, including a spectral analysis and least squares method, to analyse the monthly age-specific numbers of newly registered cases of all forms of active TB in Japan from January 1998 to December 2013. The time-series data are reported in 10-year age groups: 0-9, 10-19, …, 70-79, and ⩾80 years. We defined the contribution ratio of the 1-year cycle, Q 1, as the contribution of the amplitude of a 1-year cycle to the whole amplitude of the time-series data. The Q 1 values in the age groups corresponding to adolescence and middle life (10-39 years) and old age (⩾70 years) were high. The peaks in the active TB epidemics for the ⩾70 years age group occurred in August and September, 1-2 months behind the peaks for the 10-39 years age group (June and July). An active TB epidemic might be attributable to travel by public transport and irregular employment in the 10-39 years age group and immune system suppression by low winter temperatures in the ⩾70 years age group.
authors.affiliation: Department of Hygiene,Sapporo Medical University,Sapporo,Hokkaido,Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kohei
authors.affiliation: Department of Hygiene,Sapporo Medical University,Sapporo,Hokkaido,Japan.
authors.forename: A
authors.initials: A
authors.lastname: Sumi
authors.affiliation: Department of Hygiene,Sapporo Medical University,Sapporo,Hokkaido,Japan.
authors.forename: N
authors.initials: N
authors.lastname: Kobayashi
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012621:Seasons; D014376:Tuberculosis / Q000453:epidemiology* / Q000209:etiology; D055815:Young Adult
keywords: Age distribution; seasonality; spectral analysis; time-series analysis; tuberculosis