Short-term association between environmental factors and hospital admissions due to dementia in Madrid.
BACKGROUND
Spain has one of the highest proportions of dementia in the world among the population aged 60 years or over. Recent studies link various environmental factors to neurocognitive-type diseases. This study sought to analyse whether urban risk factors such as traffic noise, pollutants and heat waves might have a short-term impact on exacerbation of symptoms of dementia, leading to emergency hospital admission.


METHODS
We conducted a longitudinal ecological time-series study, with the dependent variable being the number of daily dementia-related emergency (DDE) hospital admissions to Madrid municipal hospitals (ICD-10 codes 290.0-290.2, 290.4-290.9, 294.1-294) from 01 to 01-2001 to 31-12-2009, as obtained from the Hospital Morbidity Survey (National Statistics Institute). The measures used were as follows: for noise pollution, Leqd, equivalent diurnal noise level (from 8 to 22h), and Leqn, equivalent nocturnal noise level (from 22 to 8h) in dB(A); for chemical pollution, mean daily NO2, PM2.5, PM1 as provided by the Madrid Municipal Air Quality Monitoring Grid; and lastly, maximum daily temperature (°C), as supplied by the State Meteorological Agency. Scatterplot diagrams were plotted to assess the type of functional relationship existing between the main variable of analysis and the environmental variables. The lags of the environmental variables were calculated to analyse the timing of the effect. Poisson regression models were fitted, controlling for trends and seasonalities, to quantify relative risk (RR).


RESULTS
During the study period, there were 1175 DDE hospital admissions. These admissions displayed a linear functional relationship without a threshold in the case of Leqd. The RR of DDE admissions was 1.15 (1.11-1.20) for an increase of 1dB in Leqd, with impact at lag 0. In the case of maximum daily temperature, there was a threshold temperature of 34°C, with an increase of 1°C over this threshold posing an RR of 1.19 (1.09-1.30) at lag 1. The only pollutant to show an association with DDE hospital admissions was O3 at lag 5, with an RR of 1.09 (1.04-1.15) for an increase of 10µg/m3CONCLUSIONS: Diurnal traffic noise, heat waves and tropospheric ozone may exacerbate the symptoms of dementia to the point of requiring emergency admission to hospital. Lowering exposure levels to these environmental factors could reduce dementia-related admissions in Madrid.
National School of Public Health, Carlos III National Institute of Health, Madrid, Spain.
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Linares
Doctoral Programme in Public Health, Autonomous University of Madrid, Spain.
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Culqui
National School of Public Health, Carlos III National Institute of Health, Madrid, Spain.
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Carmona
National School of Public Health, Carlos III National Institute of Health, Madrid, Spain.
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Ortiz
National School of Public Health, Carlos III National Institute of Health, Madrid, Spain. Electronic address: j.diaz@isciii.es.
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Díaz
D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000009:adverse effects*; D002947:Cities; D003704:Dementia / Q000139:chemically induced / Q000453:epidemiology* / Q000209:etiology; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D004781:Environmental Exposure; D004784:Environmental Monitoring; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007259:Infrared Rays / Q000009:adverse effects*; D008137:Longitudinal Studies; D008875:Middle Aged; D018986:Motor Vehicles; D009624:Noise, Transportation / Q000009:adverse effects*; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology
D000393:Air Pollutants
Air pollution; Dementia; Heat waves; Hospital admissions; Road traffic noise; Time series