Temperature and summer mortality: geographical and temporal variations in four Italian cities.
OBJECTIVE
To investigate geographical and temporal variations in the temperature-mortality relation.


METHODS
The relation between mortality and maximum apparent temperature (Tappmax) in 2003, 2004, and a previous reference period was explored by using segmented regression and generalised additive models.


METHODS
Four Italian cities (Bologna, Milano, Roma, and Torino), included in a national network of prevention programmes and heat health watch warning systems (HHWWS) were considered.


METHODS
Daily mortality counts of the resident population dying in each city during summer (June to September).


RESULTS
The impact of Tappmax on mortality differed between cities and varied in the three periods analysed. The geographical heterogeneity of the J shaped relation was seen in the reference period with Tappmax thresholds ranging from 28 degrees C in Torino to 32 degrees C in Milano and Roma. In all cities, the percentage variation in mortality was greatest in 2003. In Torino and Roma a significant increase was seen also at lower Tappmax values that are usually not associated to an increase in mortality (26-28 degrees C). In summer 2004 the exposure levels were similar to the reference period; only in Torino the effect of Tappmax on mortality remained relevant even if reduced compared with 2003, while in Bologna no statistically significant effect was seen for any temperature range.


CONCLUSIONS
The observed heterogeneous reduction in the impact of temperature on mortality from 2003 to 2004 may be partly explained by the lower levels of exposure. Changes in the ability of individuals and communities to adjust to high temperatures as a consequence of the implementation of public health interventions, based on HHWWS, characterised by a diverse effectiveness, may also have played an important part.
Michelozzi
Paola
P
Department of Epidemiology, Local Health Authority RM/E, Via di Santa Costanza 53, Rome 00198, Italy. Michelozzi@asplazio.it
De Sario
Manuela
M
Accetta
Gabriele
G
de'Donato
Francesca
F
Kirchmayer
Ursula
U
D'Ovidio
Mariangela
M
Perucci
Carlo A
CA
D000368:Aged; D000369:Aged, 80 and over; D002947:Cities / Q000453:epidemiology; D006358:Hot Temperature / Q000009:adverse effects*; D006801:Humans; D007558:Italy / Q000453:epidemiology; D009026:Mortality; D012044:Regression Analysis; D012621:Seasons; D014505:Urban Population