30-Year Trends in Stroke Rates and Outcome in Auckland, New Zealand (1981-2012): A Multi-Ethnic Population-Based Series of Studies.
BACKGROUND
Insufficient data exist on population-based trends in morbidity and mortality to determine the success of prevention strategies and improvements in health care delivery in stroke. The aim of this study was to determine trends in incidence and outcome (1-year mortality, 28-day case-fatality) in relation to management and risk factors for stroke in the multi-ethnic population of Auckland, New Zealand (NZ) over 30-years.


METHODS
Four stroke incidence population-based register studies were undertaken in adult residents (aged ≥15 years) of Auckland NZ in 1981-1982, 1991-1992, 2002-2003 and 2011-2012. All used standard World Health Organization (WHO) diagnostic criteria and multiple overlapping sources of case-ascertainment for hospitalised and non-hospitalised, fatal and non-fatal, new stroke events. Ethnicity was consistently self-identified into four major groups. Crude and age-adjusted (WHO world population standard) annual incidence and mortality with corresponding 95% confidence intervals (CI) were calculated per 100,000 people, assuming a Poisson distribution.


RESULTS
5400 new stroke patients were registered in four 12 month recruitment phases over the 30-year study period; 79% were NZ/European, 6% Māori, 8% Pacific people, and 7% were of Asian or other origin. Overall stroke incidence and 1-year mortality decreased by 23% (95% CI 5%-31%) and 62% (95% CI 36%-86%), respectively, from 1981 to 2012. Whilst stroke incidence and mortality declined across all groups in NZ from 1991, Māori and Pacific groups had the slowest rate of decline and continue to experience stroke at a significantly younger age (mean ages 60 and 62 years, respectively) compared with NZ/Europeans (mean age 75 years). There was also a decline in 28-day stroke case fatality (overall by 14%, 95% CI 11%-17%) across all ethnic groups from 1981 to 2012. However, there were significant increases in the frequencies of pre-morbid hypertension, myocardial infarction, and diabetes mellitus, but a reduction in frequency of current smoking among stroke patients.


CONCLUSIONS
In this unique temporal series of studies spanning 30 years, stroke incidence, early case-fatality and 1-year mortality have declined, but ethnic disparities in risk and outcome for stroke persisted suggesting that primary stroke prevention remains crucial to reducing the burden of this disease.
Auckland University of Technology, Auckland, New Zealand.
Valery L
VL
Feigin
Auckland University of Technology, Auckland, New Zealand.
Rita V
RV
Krishnamurthi
The University of Auckland, Auckland, New Zealand.
Suzanne
S
Barker-Collo
Health Research Council of New Zealand, Auckland, New Zealand.
Kathryn M
KM
McPherson
The University of Auckland, Auckland, New Zealand.
P Alan
PA
Barber
The University of Auckland, Auckland, New Zealand.
Varsha
V
Parag
The University of Auckland, Auckland, New Zealand.
Bruce
B
Arroll
Nuffield Department of Population Health, University of Oxford, Oxford, United Kingdom.
Derrick A
DA
Bennett
Public Health Intelligence, Ministry of Health, Wellington, New Zealand.
Martin
M
Tobias
Auckland University of Technology, Auckland, New Zealand.
Amy
A
Jones
Auckland University of Technology, Auckland, New Zealand.
Emma
E
Witt
Auckland University of Technology, Auckland, New Zealand; University of California Merced, Merced, California, United States of America.
Paul
P
Brown
Auckland University of Technology, Auckland, New Zealand.
Max
M
Abbott
Auckland University of Technology, Auckland, New Zealand.
Rohit
R
Bhattacharjee
Auckland University of Technology, Auckland, New Zealand.
Elaine
E
Rush
University of Queensland, Brisbane, Australia.
Flora Minsun
FM
Suh
Auckland University of Technology, Auckland, New Zealand.
Alice
A
Theadom
Waitemata District Health Board, North Shore Hospital, Auckland, New Zealand.
Yogini
Y
Rathnasabapathy
Auckland University of Technology, Auckland, New Zealand.
Braden
B
Te Ao
Auckland University of Technology, Auckland, New Zealand.
Priya G
PG
Parmar
The University of Sydney, Camperdown, NSW, Australia.
Craig
C
Anderson
The University of Auckland, Auckland, New Zealand.
Ruth
R
Bonita
D017677:Age Distribution; D000368:Aged; D003920:Diabetes Mellitus / Q000453:epidemiology; D005006:Ethnicity; D005260:Female; D006760:Hospitalization; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D009203:Myocardial Infarction / Q000453:epidemiology; D009520:New Zealand / Q000453:epidemiology; D012042:Registries; D012307:Risk Factors; D012907:Smoking; D020521:Stroke / Q000453:epidemiology*