Winter excess in hospital admissions, in-patient mortality and length of acute hospital stay in stroke: a hospital database study over six seasonal years in Norfolk, UK.
BACKGROUND
Several studies have examined the incidence and mortality of stroke in relation to season. However, the evidence is conflicting partly due to variation in the populations (community vs. hospital-based), and in climatic conditions between studies. Moreover, they may not have been able to take into account the age, sex and stroke type of the study population. We hypothesized that the age, sex and type of stroke are major determinants of the presence or absence of winter excess in morbidity and mortality associated with stroke.


METHODS
We analyzed a hospital-based stroke register from Norfolk, UK to examine our prior hypothesis. Using Curwen's method, we performed stratified sex-specific analyses by (1) seasonal year and (2) quartiles of patients' age and stroke subtype and calculated the winter excess for the number of admissions, in-patient deaths and length of acute hospital stay.


RESULTS
There were 5,481 patients (men=45%). Their ages ranged from 17 to 105 years (median=78 years). There appeared to be winter excess in hospital admissions, deaths and length of acute hospital stay overall accounting for 3/100,000 extra admissions (winter excess index of 3.4% in men and 7.6% in women) and 1/100,000 deaths (winter excess index of 4.7 and 8.6% in women) due to stroke in winter compared to non-winter periods. Older patients with non-haemorrhagic stroke mainly contribute to this excess. If our findings are replicated throughout England and Wales, it is estimated that there are 1,700 excess admissions, 600 excess in-patient deaths and 24,500 extra acute hospital bed days each winter, related to stroke within the current population of approximately 60 million.


CONCLUSIONS
Further research should be focused on the determinants of winter excess in morbidity and mortality associated with stroke. This may subsequently reduce the morbidity and mortality by providing effective preventive strategies in future.
Myint
Phyo K
PK
Department of Medicine for the Elderly, Norfolk and Norwich University Hospital, Norwich, UK. Pkyawmyint@aol.com
Vowler
Sarah L
SL
Woodhouse
Peter R
PR
Redmayne
Oliver
O
Fulcher
Robert A
RA
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D016208:Databases, Factual; D005260:Female; D017052:Hospital Mortality; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007902:Length of Stay; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012621:Seasons; D012737:Sex Factors; D020521:Stroke / Q000453:epidemiology* / Q000401:mortality*; D014057:Tomography, X-Ray Computed; D006113:United Kingdom / Q000453:epidemiology