Effects of noise on telephone calls to the Madrid Regional Medical Emergency Service (SUMMA 112).

BACKGROUND: Although the effects of noise on population morbidity and mortality have been observed both in the short and long term, the morbidity and mortality indicators used to date have not enabled information on such health effects to be accessed in real time. At an international level, there are relatively few studies, mostly recent, which have considered an alternative indicator, such as the demand for medical attention provided by emergency services, taking into account environmental factors other than noise.

OBJECTIVES: To ascertain the short-term effect of road-traffic noise levels on medical care, broken down by organic, circulatory and respiratory causes, provided by the Madrid Regional Medical Emergency Service (Servicio de Urgencia Médica de Madrid/SUMMA 112).

METHODS: We used an ecological time-series study and fitted Poisson regression models, to analyse the number of daily, cause-specific episodes of care provided in situ by SUMMA 112, via emergency ambulance dispatches, across the period 01/01/2008-31/12/2009. To this end, we considered diurnal (Leqd: 7-23h), nocturnal (Leqn: 23-7h) and daily (Leq24: 24h) noise (in db(A)) as the principal factor, and chemical air pollution (µg/m3 ) and temperature (°C) as the control variables. We also controlled for trend and seasonalities, the autoregressive nature of the series, and day of the week.

RESULTS: Nocturnal noise exceeded the WHO threshold (55 db(A)) on 100% of nights, despite displaying a downward trend across the study period. For all causes, with the exception of emergency calls due to ischaemic disease, it was nocturnal rather than diurnal noise levels that had a short-term effect (lags 0-1) on SUMMA 112 calls, with this impact being greater for respiratory than for circulatory causes. Hence, for every increase of 1db in Leqn, the relative risks (RRs) were as follows: 1.11 (95% CI 1.09-1.13) for organic causes; 1.14 (95% CI: 1.11-1.18) for respiratory causes; and 1.08 (95% CI: 1.05-1.10) for circulatory causes.

CONCLUSION: SUMMA 112 data give access to real-time information on the health effects associated with increases in noise levels, which cannot be obtained via mortality or hospital-admission data, since these are collected in the longer term. Accordingly, this is something that would be immediately applicable in any future implementation of a syndromic surveillance system focusing on the effects of environmental pollutants on health.