Incidence of multiple sclerosis in Northern Lisbon, Portugal: 1998-2007

• Published in: BMC neurology Vol. 14; no. 1; p. 249
• Main Authors: de Sá, Joao, Alcalde-Cabero, Enrique, Almazán-Isla, Javier, García-López, Fernando, de Pedro-Cuesta, Jesús
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 21-12-2014; BioMed Central
• Subjects: Adolescent; Adult; Age Distribution; Aged; Cities; Diagnosis; Epidemiology; Female; Health facilities; Hospitals; Humans; Incidence; Male; Middle Aged; Multiple sclerosis; Multiple Sclerosis - epidemiology; NMR; Nuclear magnetic resonance; Portugal - epidemiology; Sex Distribution; Studies; Surveys; Young Adult; Portugal
• ISSN: 1471-2377; 1471-2377
• DOI: 10.1186/s12883-014-0249-1

There are few, recent, well assessed, multiple sclerosis (MS) incidence surveys on European populations. This study sought to measure MS incidence in a Northern Lisbon population and assess it using capture-recapture methods (CRMs).
Among the population residing in the Northern Lisbon Health Area, registered MS diagnoses were obtained from general practitioners in three primary-care districts covering a population of 196,300, and a neurology unit at the main referral hospital. Cases with onset during the periods 1978-1997 and 2008-2012 were excluded due to perceived poor access to image-supported neurological diagnosis and administrative changes in patient referral respectively. Age- and sex-specific incidences for the period 1998-2007 were calculated using McDonald diagnostic criteria, and CRMs were used to correct age-specific incidence rates. The corrected figures were also adjusted for age using the European Standard Population as reference.
When applied to 62 MS patients with onset in the period 1998-2007, the rates per 100,000 population were as follows for both sexes: crude, 3.16; age-adjusted, 3.09 (95% CI 2.32 to 3.87); CRM-adjusted, 4.53 (95% CI 3.13 to 5.94); and age- and CRM-adjusted, 4.48 (3.54-5.41). In general, the rates were 3-fold higher among women than among men. Negative source dependency and CRM impact were highest at ages 35-44 years, where a 60% rise led to a peak incidence.
MS incidence in Northern Lisbon, Portugal, is moderately lower than that yielded by surveys on European populations. CRMs, which in this instance suggest undercounts, are a potentially useful tool for case-finding assessment but their application may introduce bias.