Night noise guidelines for Europe - WHO/Europe - World Health ...

96 EFFECTS ON HEALTH
have had experience with persons suffering very much from sleep disturbance due to
high traffic noise exposure, whilst his/her OSAS or primary insomnia patients
happened to be light cases. One must accept that even GPs have a limited experience
with the whole range of cases of each of the three types of insomnia, so
that their opinion on the mean severity of noise-related sleep disturbance, compared
to the mean severity of OSAS or insomnia, is influenced by the randomness
of their patient mix.
Nevertheless, the table supports the following statements.
• With respect to severity, the majority of GPs rank noise-related sleep disturbance
lower than insomnia and OSAS, while three of them put noise-related sleep disturbance
in the first rank. Only one of the participants (number 21) considers
noise-related sleep disturbance as a fully negligible disturbance.
• The severity ratio between noise-related sleep disturbance and insomnia varies
between 0 and 2.1. Seven of the fourteen GPs indicate a severity ratio between 0.5
and 0.75, that is to say that half the participants are of the opinion that the severity
of noise-related sleep disturbance amounts to 50–75% of the severity of
insomnia.
• The mean of this severity ratio is 0.89, with a standard deviation (sigma) of 0.60.
The confidence interval (CI) for the mean goes from 0.58 to 1.20. The median of
the severity ratio is 0.63. The distribution is skewed to the right.
The severity ratio developed above can be used as a proportionality factor between
the known disability weight for insomnia and the required disability weight for selfreported
sleep disturbance. Bearing in mind that the already existing WHO disability
weight for insomnia is 0.10, a best guess for the mean disability weight for selfreported
sleep disturbance due to road traffic noise at night is therefore 0.089, with
a CI from 0.058 to 0.12.
4.9.4 CONCLUSIONS
According to the two groups of interviewed medical professionals, persons that
declare themselves to be chronically deprived of normal sleep by road traffic noise
have a health state whose mean disability weight is comparable to “chronic hepatitis
B infection without active viral replication” or higher. Irrespective of the question
whether self-reported sleep disturbance is formally recognized as a disease or not, its
severity is comparable to commonly accepted diseases.
The best estimate for a mean disability weight for self-reported sleep disturbance due
to road traffic noise was 0.055 (CI: 0.039; 0.071) according to Müller-Wenk (2002),
whilst our recheck based on a comparison with insomnia resulted in a disability weight
of 0.09 (CI: 0.06; 0.12). The higher disability weight according to the second approach
might be caused by the fact that in this second approach, there was a stronger focus
on “the person’s condition during the day after the sleep-disturbed night”.
The above figures compare reasonably with a study published by van Kempen
(1998), cited in Knol and Staatsen (2005:46), where a severity weight of 0.10 for
severe sleep disturbance was found, based on the judgement of 13 medical experts
according to the protocol of Stouthard et al. (1997).
NIGHT NOISE GUIDELINES FOR EUROPE