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Cephalalgia
http://cep.sagepub.com/content/early/2010/11/24/0333102410385580
The online version of this article can be found at:
DOI: 10.1177/0333102410385580
published online 26 November 2010Cephalalgia Wöber
Karin Zebenholzer, Ernest Rudel, Sophie Frantal, Werner Brannath, Karin Schmidt, Çiçek Wöber-Bingöl and Christian
Migraine and weather: A prospective diary-based analysis
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Original Article
Migraine and weather: A prospective
diary-based analysis
Karin Zebenholzer
1
, Ernest Rudel
2
, Sophie Frantal
1
,
Werner Brannath
1
, Karin Schmidt
3
,C¸ic¸ek Wo
¨ber-Bingo
¨l
1
and
Christian Wo
¨ber
1
Abstract
Aims: Weather is mentioned as a trigger factor by migraine patients most frequently. We examined the impact of
meteorological factors and the impact of their day-to-day change on the risk of occurrence and persistence of headache
and migraine and the correlation of subjective weather perception with objective weather data.
Methods: We performed a prospective, diary-based cohort study in 238 patients suffering from migraine with or without
aura. Patients had to live within 25 km of the Vienna meteorological station and were required to keep a diary for 90
days. We analysed 11 meteorological parameters and 17 synoptic weather situations. For evaluating the hazard of
occurrence and persistence of migraine and headache, we performed a univariate and a stepwise multivariate Cox
regression analysis. We calculated correlations between subjective weather perception and meteorological data.
Results: In the uni- and multivariate analysis, a ridge of high pressure increased the risk of headache occurrence, lower
mean daily wind speed increased the risk of migraine occurrence and a day-to-day change of daily sunshine duration
increased the risk of migraine occurrence. A day-to-day change of the daily minimum temperature decreased the risk of
migraine persistence. After correction for multiple testing, none of these findings remained statistically significant.
Subjective weather perceptions did not correlate with the occurrence or persistence of migraine or headache.
Subjective perception of cold and too-cold weather and of too-warm weather correlated with daily minimum, mean
and maximum temperature.
Conclusion: The influence of weather factors on migraine and headache is small and questionable.
Keywords
Migraine, headache, weather, trigger factors, weather changes
Date received: 31 March 2010; revised: 18 June 2010; accepted: 24 August 2010
Introduction
Weather is one of the trigger factors mentioned by
patients most frequently (1–3). Sensitivity to meteoro-
logical changes is reported by 30–78% of headache
patients (1,4). Patients relate headache most commonly
to rapidly falling atmospheric pressure (2,5–7). Other
weather characteristics suspected to precipitate head-
ache include seasonal changes, bright sunshine, strong
winds, hot weather, cold weather or thunderstorms
(2,5–8). In contrast to the conviction of many patients
that weather contributes to the occurrence of head-
aches, studies on the relationship between various mete-
orological variables and headaches or migraine have
yielded inconsistent results. Most studies examined
the effect of weather variables on migraine frequency
and many of them failed to prove a statistically
significant relationship (9–12). In some studies, air tem-
perature, atmospheric pressure and wind speed were
related to an increase and in others to a decrease in
migraine frequency (6,11,13,14). In addition, the influ-
ence of certain weather characteristics varied in one and
the same study (9,10,12,14–16).
1
Medical University of Vienna, Austria.
2
Central Institute of Meteorology and Geodynamics, Austria.
3
Donauspital Vienna, Austria.
Corresponding author:
Christian Wo
¨ber, Department of Neurology, Medical University of
Vienna, Wa
¨hringer Gu¨rtel 18-20, 1090 Vienna, Austria
Email: christian.woeber@meduniwien.ac.at.
Cephalalgia
0(0) 1–10
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The underlying mechanisms of possible associations
between weather and headaches are not understood.
It was speculated that sferics (very low frequency atmo-
spherics, i.e. pulse-shaped, alternating electric and mag-
netic fields of very short duration which originate from
atmospheric discharges) play a major causal role
(17,18). The influence of atmospheric pressure or
Saharan dust on trigeminal structures was examined
in two animal models. One study found that the
spinal trigeminal nucleus in rats responded to lowering
atmospheric pressure and speculated that neuronal acti-
vation during atmospheric pressure changes may
explain weather-related headaches (19). A recent
study showed that Saharan dust containing naturally
found microorganisms activates the trigeminovascular
system in rats (20). Microorganisms such as bacteria,
viruses, fungi and their spores attached to Saharan dust
could multiply and initiate a series of reactions upon
contact with cloud water and solar energy. This results
in an increase in the number of microorganisms, basic
amino acids, some metals, bioavailable iron and some
unknown particles. The nociceptive effect of African
dust is attributed to a nonoparticle (20). In addition,
it was speculated that excretion of serotonin or hista-
mine caused by positive ionisation of the ambient air
may induce migraine (21). Still, no plausible pathophys-
iological model exists.
In the present study, we sought to analyse in detail
weather-related data from a large prospective diary
study including a wide range of factors related to
migraine (22). Overall findings of this study, published
previously, demonstrated that menstruation increased
the risk for occurrence of a migraine attack by up to
96%, whereas other factors (muscle tension in the neck,
psychic tension, tiredness, noise and odours increased
the risk by no more than 35% (22). In addition, the
study showed favourable as well as unfavourable effects
of some meteorological factors. In this paper, we pre-
sent detailed findings on the relation of headache in
general and migraine in particular to (i) single weather
values, (ii) day-to-day changes in these values, (iii) a
synoptic weather classification and (iv) the patients’
subjective perception of weather conditions.
Furthermore, we analysed the relation between objec-
tive meteorological data and the subjective perception
of weather.
Patients and methods
Patients were recruited via newspaper advertisements
about trigger factors of migraine. Inclusion criteria
comprised written informed consent, age 18years, a
migraine frequency of at least one attack per month
during the past six months and a diagnosis of migraine
without aura, migraine with aura or probable migraine
(with or without co-existing tension-type headache)
according to the International Classification of
Headache Disorders, second edition (ICHD-II) (23).
All patients were seen personally at the clinic and diag-
nosis was made by one of the authors (CW). Patients
with medication overuse headache, other primary or
secondary headaches and other clinically relevant dis-
eases (stroke, unstable or acute coronary heart disease,
other vascular disorders, marked hypertension, neuro-
logical, pulmonary, hepatic, renal or endocrine disease
and active malignant diseases) were excluded. The
study was approved by the ethics committee of the
Medical University of Vienna and Vienna General
Hospital.
Patients included underwent a semi-structured inter-
view, filled in paper-and-pencil questionnaires and were
required to keep a detailed headache diary.
Methodological details have been published elsewhere
(22). In summary, biographic data, lifestyle, general
medical history and headache characteristics were
recorded and patients were provided with a paper-
and-pencil diary for 90 days. The diary was filled in
every day before bedtime, irrespective of the presence
or absence of headache, and covered 59 items poten-
tially related to migraine. All items had to be assessed
on a four-point scale or a quantity had to be given.
Seven questions referred to the subjective perception
of the weather. In addition, the diary covered questions
regarding the presence of headache as well as all head-
ache characteristics required for diagnosis according to
ICHD-II. Each single headache was classified accord-
ing to the ICHD-II criteria for migraine without aura
(23). Headaches fulfilling none of the criteria B, C and
D, (headache duration, headache characteristics and
associated symptoms) were excluded from further anal-
ysis. Headaches fulfilling one criterion were classified as
non-migrainous and those fulfilling two or three criteria
as probable migraine and migraine, respectively.
Meteorological data were collected on a daily basis
at the Central Institute of Meteorology and
Geodynamics, Vienna, Austria, between 1 October
2002 and 31 March 2003. Due to the geographical
and meteorological situation, these data are reliable
for an area of 25 km around the institute (linear dis-
tance). Eleven single values, such as air temperature or
atmospheric pressure, were measured every 10 minutes.
Based on all these single values, minimum and maxi-
mum values, means with standard deviations and sums
were calculated for further analysis as appropriate.
In addition, we used a synoptic weather classification
differentiating 17 different weather situations. This syn-
optic classification represents macro weather situations
in the eastern Alps characterised by typical constella-
tions of pressure gradient between ground level and
heights, horizontal and vertical air convection, low
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pressure areas and air advection. The macro weather
situations of the eastern Alps are in fact those weather
situations which regulate the local weather in and
around Vienna. The weather situations occur irregu-
larly during the year and determine the local weather
for shorter or longer periods (24). The classification was
done once a day, at 7 A.M.
Statistical analysis
The statistical analysis was based on the interval
between two headache attacks and on the interval
between two migraine attacks. The analysis of head-
ache and migraine attacks was based on 20,553 patient
days. For analysing the occurrence of headache and
migraine, each interval started on the second day
after a headache or migraine and ended on the day of
the following attack. The first day without headache
was excluded from statistical analysis, as on this day
the risk of headache and migraine was per definition 0
and covariates could have been influenced by the head-
ache the day before. To evaluate the hazard of occur-
rence of headache and migraine, we performed
univariate Cox regression analyses and a stepwise mul-
tivariate Cox regression analysis including those covari-
ables which showed statistically significant results in the
univariate procedure. Details of the statistical model
have been published previously (22). All continuous
covariables were categorised in either two or three
approximately equally large classes (leading to either
a single or two dichotomous covariables). In total,
116 dichotomous covariables were investigated. For
analysis of the persistence of headache and migraine
attacks, we performed similar calculations based on
the interval between the day after headache or migraine
onset and the first headache (migraine) free day, defin-
ing persistence as presence of headache or migraine on
at least two subsequent days. The hazard ratio for an
increase in persistence is <1, because the ‘‘hazard’’ of
ending the attack is decreased. Considering that many
patients believe that they get headache or migraine
immediately before or after a change of weather, we
calculated the day-to-day changes in the mean values
of the 11 single weather values and included these mean
values of change in the multivariate analysis.
Correlations between subjective weather perception
and single weather values, correlations between subjec-
tive weather perception and the mean day-to-day
changes of the weather values and correlations between
subjective weather perception and the occurrence of
migraine or headache were calculated using
Spearman’s correlation coefficient. The statistical anal-
ysis was based on patient days and on all separately
diagnosed headache and migraine attacks, and not on
individual patients. For all tests, significance levels were
set at p<.05. After performing correction for multi-
ple testing by means of Bonferroni correction, only
pvalues <.0018 were considered significant. All analy-
ses were performed with the statistical software pack-
age R. (A language and environment for statistical
computing. Development core team organisation.
Foundation for statistical computing. Vienna, Austria)
Results
Of 446 patients screened, 397 were included in the orig-
inal study and 327 completed that study (22). For the
present study, we selected those 287 patients living
within 25 km of the Central Institute of Meteorology
and Geodynamics. Diaries were available from 238
patients (209 women, 29 men) aged 42.2 12.1 years
and suffering from migraine for 20.0 12.3 years.
Demographic characteristics of the patients are shown
in Table 1. The patients kept the diary for 86.4 12.8
days (range 12–104 days). The number of patient days
on each day of the study period is shown in Figure 1.
Headache was present on 5281 days of 20,553 patient
days; of these, migraine (including migraine without
aura, migraine with aura and probable migraine
according to ICHD-II) was diagnosed on 3404 patient
days. Migraine with aura was present on 513 patient
days. The mean duration of all headache attacks was
7.1 5.3 hours, and the mean duration of migraine
attacks was 8.1 5.5 hours. The intensity of all head-
ache attacks was severe in 30.0%, moderate in 43.4%
and mild in 26.6%. Looking at migraine attacks in
detail, the intensity was severe in 40.0%, moderate in
47.5% and mild in 12.5%.
Table 1. Patients’ baseline data
Variable
Age Years, mean SD 42.2 12.1
Sex Women, % 87.8
Marital status Living with partner, % 45.8
Number of children Having at least one child, % 58.0
Education 12–13 years of education, % 80.3
Occupation Employees, % 74.8
Time since onset
of migraine
Years, mean SD 19.9 12.3
Migraine days
per month
N, mean SD 6.3 5.8
Medication for
headache attacks
Using triptans, % 28.0
Prophylactic
medication
Present, % 7.2
Hormonal
contraception
Present, % 31.5
SD ¼standard deviation.
Zebenholzer et al. 3
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Single weather values and day-to-day changes of
these values are shown in Table 2, and the synoptic
weather classification is summarised in Table 3. The
prevalence of weather situations during the study
period was typical of the overall weather situations in
the eastern Alps. Table 3 shows also the prevalence of
the weather situations on the day before headache
onset, the first headache day, all other headache days
and all other headache-free days.
Among the non-meteorological factors, the risk of
occurrence of headache and migraine was increased
most prominently on days 1 to 3 of the menstrual
period. Further details are shown in Tables 4A and 4B.
In the uni- and multivariate analyses, only one
weather situation had a statistically significant influence
on the occurrence of headache: a ridge of high pressure
increased the risk of getting headache (Table 4A).
Among the single weather values, only a lower daily
mean wind speed increased the risk of getting migraine
(Table 4A). A day-to-day change of daily sunshine
duration slightly increased the risk of getting migraine
(Table 4A). There was only a minimal decrease in the
risk of migraine persistence due to an increase in day-
to-day minimum air temperature (Table 4B). However,
after correction for multiple testing, the influence of
these weather factors was no longer statistically
significant.
The patients’ subjective perception of certain
weather aspects is summarised in Table 5. The patients’
perceptions did not correlate with the occurrence or
persistence of migraine or headache (r 0.2, p>.05).
Because many patients report that the occurrence of
Figure 1. Number of patient days on each day of the study period.
Table 2. Weather characteristics during the study period*
Weather value Unit Daily mean Minimum Maximum Mean value of change
Minimum air temperature C 0.01 5.4 13.7 14.7 0.05 2.9
Mean air temperature C 3.2 5.7 9.1 17.0 0.06 2.7
Maximum air temperature C 6.4 6.7 7.7 21.5 0.05 3.5
Minimum atmospheric pressure hPa 990.0 10.0 966.9 1010.8 0.06 5.8
Mean atmospheric pressure hPa 992.9 9.7 957.9 1012.5 0.02 7.9
Maximum atmospheric pressure hPa 996.0 8.8 970.9 1014.0 0.05 5.6
Mean wind speed m/s 3.3 1.6 0.8 9.5 0.001 1.8
Maximum wind speed m/s 11.1 4.8 3.4 27.4 0.01 5.4
Sum of sunshine duration Hours/day 3.0 3.5 0 11.9 0.1 3.5
Mean relative humidity % 77.0 11.5 42 96 0.2 10.1
Sum of precipitation L/m
2
1.5 3.0 0 18.0 0.08 3.9
*Daily means with standard deviation, minimum and maximum values, and means of day-to-day changes with standard deviation. m/s ¼meters per
second. hPa ¼Hectopascal. L/m
2
¼litres per square meter.
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headache or migraine is associated with the subjective
perception of heat, cold, wind or annoying sunshine, we
analysed correlations between the subjective perception
of these parameters and the objective weather values.
The patients’ perceptions of cold and too-cold weather
correlated with the daily minimum, mean and maxi-
mum temperature (0.3 <r<0.4, p<.0001). In addition,
the subjective perception of too-warm weather corre-
lated with the perception of daily minimum, mean
and maximum temperature (r ¼0.3, p<.0001).
Discussion
In this comprehensive prospective diary study, we ana-
lysed 20,553 patient days recorded by 238 patients with
migraine. We classified each single headache attack
according to ICHD-II (23), and we found very limited
influence of meteorological factors on the occurrence
and persistence of headache and migraine in migraineurs.
We found some influence of a lower daily mean wind
speed and the change of sunshine duration on the risk of
migraine, occurrence and of the change of daily minimum
air temperature on the risk of migraine persistence. Of 17
synoptic weather situations, only a ridge of high pressure
increased the risk of headache occurrence. However, after
correction for multiple testing, none of these findings
remained statistically significant. The patients’ subjective
perception of weather did not correlate with the
occurrence or persistence of headache or migraine. The
relation between the patients’ perception and objective
meteorological data was limited to a few correlations.
The findings on non-meteorological factors were in agree-
ment with those of the overall analysis published previ-
ously (22), although a smaller number of subjects was
analysed, because patients who lived in a distance of
more than 25 km from the meteorological institute were
excluded. In relation to these trigger factors, the influence
of meteorological factors is a minor one.
Performing a comprehensive Medline search using
the terms ‘‘migraine’’, and ‘‘weather’’, ‘‘meteorolog*’’,
‘‘air temperature’’, ‘‘atmospheric pressure’’, ‘‘sunshine’’,
‘‘wind’’, ‘‘humidity’’, ‘‘precipitation’’, ‘‘rain’’, ‘‘snow’’
and ‘‘sferics’’, we found only 13 original papers report-
ing examinations of the relation of migraine and various
meteorological parameters. The methods of these stud-
ies are summarised in Table 6. Some cumulative findings
are summarised in Table 7. Three studies published
between 1979 and 1990 were entirely negative, reporting
no influence of meteorological factors such as wind
speed, wind direction, temperature, relative humidity
or atmospheric pressure on the frequency, intensity or
duration of headaches (10,12,16). In two studies, the
only statistically significant findings were favourable
(15,25). The other studies revealed at least some unfa-
vourable effects of weather on migraine
(6,9,11,13,14,26). Four studies investigated the
Table 3. Prevalence of various weather situations during the study period, based on all patient days
Synoptic weather classification
All days
(%)
Days before headache
onset (%)
Days of headache
onset (%)
All other headache
days (%)
All other headache-
free days (%)
Air advection from west 14.7 14.0 13.4 14.9 15.0
High pressure 12.1 12.6 12.3 11.2 12.3
High pressure over Fennoskandia 9.5 8.8 9.2 9.3 9.7
Low pressure over Central Europe 7.6 7.8 7.5 7.9 7.6
Low pressure in the south 7.3 7.7 7.2 7.6 7.3
Air advection from the northwest 7.1 7.2 7.2 7.1 7.0
Air advection from the north 7.1 7.0 7.3 6.4 7.2
Zonal high pressure 6.6 5.6 6.3 7.1 6.8
High pressure in the east of Europe 5.2 4.6 4.9 4.8 5.4
Ridge of high pressure 5.1 5.7 6.2 6.1 4.6
Air advection from the southwest 4.2 5.0 4.8 4.4 3.9
Trough 3.9 4.3 4.2 3.8 3.8
Weak pressure gradient 3.3 3.8 2.6 3.1 3.3
Air advection from the south 2.7 2.8 2.4 3.3 2.6
Low pressure over Britain 2.5 2.6 3.2 2.1 2.4
Low pressure in the western
Mediterranean area
0.6 0.7 0.8 0.5 0.6
Low pressure on the route Vb 0.6 0.5 0.7 0.7 0.6
A day before headache onset is the last headache-free day before the day of headache onset. Low pressure on route Vb ¼low pressure typically
spreading from south Italy to north Italy, Austria and Hungary.
Zebenholzer et al. 5
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association between sferics, geomagnetic activity and
migraine (17,18,27,28). But a correlation between
increased sferics activity and increased migraine fre-
quency was found in autumn only, not during summer
months, and in just one of these studies (17).
Neurophysiologically, the alpha band of the EEG was
found to be influenced by sferics activity in healthy per-
sons and in patients suffering from migraine or tension-
type headache (29,30).
The trend towards headache risk being increased by
a ridge of high pressure is in accordance with the study
of Walach et al. (14), who reported an increased
migraine frequency during warm high pressure, exag-
gerated high pressure and warm air advection at the rim
of high pressure. However, in contrast to our study,
which was done in autumn and winter, Walach et al.
(14) found these correlations during summer months
only. Furthermore, in our study, this trend was found
for all headache days and not specifically for migraine
days. Considering that many patients relate headache
and migraine to weather changes (3,4), we included
day-to-day changes of single weather values in our
analyses, something which was done in only one
study previously (15). The previous as well as the pre-
sent study suggest that these day-to-day changes play a
very limited (if any) role.
The considerable discrepancy between subjective
weather perception and objective weather values in
our study confirms previous studies. Prince et al. (6)
reported that about 50% of their patients were sensitive
to any weather factor (mostly to a function of absolute
temperature and humidity), and 62.3% thought they
were sensitive to weather conditions. However, the
weather conditions subjectively reported as headache
triggers did not correlate with the ones found in the
analysis of the objective parameters. Similar discrepan-
cies were reported by Cooke et al. (13). Once more, this
underlines that we cannot rely only on patients’ reports
of possible triggers and that objective measurements are
Table 4B. Factors showing a significant influence on the
persistence of headache or migraine in uni- and multivariate
Cox regression analysis
Stepwise multivariate Cox
regression analysis with robust
variance estimates
Hazard
ratio
a
Robust stderr
of estimate
b
pvalue
Headache attacks
Progesterone-only
contraception
1.37 0.14 .026
Divorced marriage 1.32 0.095 .0036
Academic degree 1.17 0.077 .039
Relaxation after stress 1.14 0.055 .019
Chocolate 1.11 0.045 .025
Private stress 0.89 0.055 .025
Muscle tension in the neck 0.86 0.061 .011
Noise 0.85 0.064 .01
Menstruation days 1–3 0.81 0.074 .0036
Menstruation days 4þ0.77 0.094 .0055
Migraine attacks
Consumption of beer 1.30 0.094 .0053
Nine years of education 1.28 0.097 .011
Divorced 1.26 0.096 .016
Relaxation after stress 1.21 0.061 .0016
Day-to-day change of
minimum air temperature
1.02 0.007 .023
Odours 0.86 0.068 .022
Menstruation days 1–3 0.84 0.077 .021
Other diseases 0.83 0.081 .018
Noise 0.83 0.084 .026
a
The hazard ratio for an increase in persistence is <1, as the ‘‘hazard’’ of
ending the attack is decreased.
b
stderr ¼standard error.
pvalues in bold indicate significant results after Bonferroni correction.
Table 4A. Factors showing a significant influence on the
occurrence of headache or migraine in uni- and multivariate Cox
regression analysis
Stepwise multivariate Cox
regression analysis with
robust variance estimates
Hazard
ratio
Robust stderr
of estimate
a
pvalue
Headache attacks
Menstruation days 1 to 3 1.82 0.077 <.0001
Menstruation days 4þ1.53 0.097 <.0001
Ridge of high pressure 1.24 0.089 .0160
<3 hours sport per month 1.23 0.068 .0026
Tiredness 1.21 0.051 .0002
Psychic tension 1.16 0.052 .0045
Mental exhaustion 1.14 0.051 .0079
Holidays/days off 0.86 0.056 .0064
Migraine attacks
Menstruation days 1–3 1.95 0.083 <.0001
Menstruation days 4þ1.42 0.113 .0020
Psychic tension 1.24 0.060 .0003
Muscle tension in the neck 1.18 0.076 .0280
Lower daily mean wind speed 1.11 0.047 .024
Day-to-day change of
sunshine duration
1.02 0.008 .0430
Academic degree 0.75 0.098 .0034
Holidays/days off 0.83 0.062 .0022
a
stderr ¼standard error.
pvalues in bold indicate statistically significant results after Bonferroni
correction.
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warranted, collected independently of the patients’ per-
ception (31). We think that the discrepancy between
subjective perception and objective weather data
could be explained by the patients’ search for causal
explanation and selective memory. It may be more
likely to recall the co-occurrence of bad weather and
headache than bad weather without headache or good
weather with or without headache. This hypothesis may
be supported by a study on stressful events in patients
with tension-type headache. It suggested that patients
as well as headache-free persons have a tendency to
overestimate stress on retrospective measures (34).
The examination of pathophysiological mechanisms
which could link headache and weather was not the
goal of the present study. Neither does our study
allow any pathophysiological conclusions, nor does it
show a consistent factor which could be the goal of
experimental or pathophysiological studies on the asso-
ciation of weather and headache.
Regarding the interpretation of previous studies, one
has to consider various methodological issues. As
shown in Table 6, most studies did not establish diag-
noses according to the classification of the
International Headache Society but according to
ICHD-I or the Ad hoc criteria (32,33). Diaries were
used in the majority of studies, but information was
usually limited to the absence or presence of headache.
Detailed headache characteristics and classification of
each single headache attack as suggested by Lipton (33)
were used in two studies only (9,13) and in one study
partially (12). Observation periods varied from four
weeks to six months and covered different seasons.
Only two studies (13,15) had longer observation peri-
ods and covered all seasons. Correction for multiple
testing was explicitly done in only one study (17). The
geographical area around the weather station was
defined unequivocally in seven studies only. Such defi-
nition is necessary, however, since the reliability of
Table 6. Migraine and weather: methodology of previous studies
Authors
Patients
(N)
HA
classification
HA
type Prospective Diary Period
Defined
area
Multivariate
analysis
Gomersall & Stuart, 1973 (9) 56 Ad hoc (31) M þþ?þ–
Wilkinson & Woodrow, 979 (10) 310 Ad hoc M þTTH þ
a
–––
Schulman et al., 1980 (16) 75 Ad hoc M þþ4 weeks þ–
Cull, 1981 (15) 44 Ad hoc? M þþ2 years þ?–
Osterman et al., 1981 (11)
b
73 Ad hoc M þTTH þþ4 weeks þ?þ
Diamond et al., 1990 (12) 100 Ad hoc M þþ2–6 months – –
Vaitl et al. 2001 (17) 37 ICHD-I? (32) M þTTH þþ6 months þ?–
Walach et al. 2001 (18) 21 ICHD-I M þTTH þþ?þ
Walach et al., 2002 (14) 98 ICHD-I M þTTH þþ18 weeks þþ
Prince et al., 2004 (6) 77 ICHD-I M þþ2 months þþ
Villeneuve et al., 2006 (25) 4039 ICD-9 M þTTH
a
–þþ
Cooke et al., 2007 (13) 75 ICHD-I M þþ58–485 days þþ
Mukamal et al., 2009 (26) 7054 ICD-9 M
a
–þþ
HA ¼headache. M ¼migraine. TTH ¼tension-type headache . Ad hoc ¼Ad hoc committee on classification of headache of the National Institute of
Health. ICD-I ¼International Classification of Diseases, first edition. ICHD-9¼International Classification of Headache Disorders, ninth revision.
a
Only one hospital visit.
b
Statistical analysis was done for 53 migraineurs only.
Table 5. Percentage of patients who have the subjective perception of the presence of certain weather aspects (based on all patient
days)
Subjective weather
perception
All
days
Days before
headache onset
Days of headache
onset
All other
headache days
All other headache-
free days
Heat 3.6 3.4 4.8 5.2 3.1
Cold 37.0 37.0 40.4 40.2 35.6
Change of weather 23.3 22.5 36.1 34.6 18.4
Annoying wind 24.7 25.6 29.9 30.6 22.2
Annoying sun glare 4.4 4.6 7.6 7.1 3.2
Too-warm weather 10.6 9.5 12.8 16.0 9.2
Too-cold weather 30.4 31.6 33.0 34.2 28.8
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weather values is limited to a certain area around the
weather station. In addition, special methodological
aspects must be considered: two studies examined the
association between weather and emergency room visits
due to migraine or headache attacks (25,26). Both stud-
ies used a case-crossover design which assumes that an
event does not occur on a pre-specified control day.
Patients were not interviewed about whether they had
headache on this control day. Accordingly, the infor-
mation in both studies is limited to the risk of an emer-
gency room visit because of headache or migraine, and
does not allow any conclusions regarding the relation
of certain meteorological factors to the presence or
absence of headache or migraine. In addition, emer-
gency room visits depend on various factors, such as
patient selection, emergency department availability,
subjective perception of pain, co-morbid depression
or disease severity (35), which might have caused addi-
tional bias. Weather is only one co-factor which may
influence the decision to visit an emergency department.
Accordingly Villeneuve et al. (25) asserted that their
study was more an investigation on ‘‘visits to a hospital
for migraine’’ and weather than on migraine
and weather. In addition, in these studies, the actual
onset of headache attacks could not be recorded
(25,26).
An important issue in studying the influence of
weather on headaches is the dynamic nature of weather.
Single weather values can change significantly during
one day; synoptic weather classifications are not
always stable during one day and can change within
hours or over days. Furthermore, each classification
means to arbitrarily assign hundreds of weather
values and types to only few weather classes. So far,
neither our study nor previous studies could manage
this challenge sufficiently.
Strengths and limitations
Our study has several strengths and limitations.
Strengths are the large number of patients and patient
days, the prospective collection of data using a diary
which allowed classification of each single headache
attack according to ICHD-II (23), the fact that the
patients were blinded regarding the collection of objec-
tive weather values and the analysis of weather-related
variables in the context of other possible trigger factors.
In addition, the sophisticated statistical analysis is an
important strength of this paper. Analysis of this type
of data is not an easy task and is still under statistical
scientific discussion (36,37). To our knowledge, for the
examination of associations between migraine and
weather, such complex models have been used for the
first time. The models chosen in this paper have the
following advantages. First, they allow analysing recur-
rent data. Second, they allow accounting for time-vary-
ing covariates. Third, they account for censoring due to
the 90-day study window and other independent drop-
out. Fourth, using the robust variance estimate
accounts for the correlation of event times of the
same subject when estimating the standard errors.
The confirmatory analysis with strata based on the
number of headache intervals per patient was done to
see whether the significant factors found in the main
model are mainly driven by few patients with a large
number of intervals. Factors that do not rely on few
patients with a large number of intervals should be sig-
nificant also in the stratified model.
Our study is limited, most importantly, by the obser-
vation period restricted to the half-year between
October and March. In addition, weather classification
was done only once a day and the weather class may
have changed during the day. Comparing the meteoro-
logical findings during the study period with long-term
findings, however, did not indicate that weather condi-
tions were unusually stable or unstable during the
study. Furthermore, regional geographical variety
may have influenced specific weather characteristics,
and we did not analyse local weather differences
caused by the topographical relief. However, local
weather and its local differences are regulated by the
Table 7. Influence of various single weather values or combined
weather factors on migraine frequency: findings of previous
studies (figures given are numbers of studies)
Weather
parameter
Influence on migraine
occurrence/frequency
Total number
of studies Increase Decrease
No
change
Air temperature 6
a
10
a
5
Atmospheric
pressure
8
a
11
a
6
Sunshine 2 0 0 2
Humidity 5 0 0 5
Fog 1 0 0 1
Thunderstorms 2 0
a
11
Wind speed 5
b
1
a
13
Chinook winds 1 1 1 0
Precipitation 2 0 0
a
2
Cloudiness 2 0 0
a
2
Combined
weather factors
4311
Sferics activity 2 2 2 2
a
Two studies examined the number of emergency room visits due to
migraine attacks and concluded that the risk of migraine occurrence
was influenced.
b
In combination with pre-Chinook days.
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macro weather situation and that regulates the local
weather within 25 km around the Central Institute of
Meteorology and Geodynamics. Accordingly, we
selected all patients living within this distance. In addi-
tion, one has to consider that many patients work in
districts other than the area they live in. Therefore, the
procedure chosen was the best possible for studying the
influence of weather on headache and migraine guar-
anteeing an optimum in geographical and meteorolog-
ical homogeneity. The findings regarding the weather
situations are limited to the studied specific area, but
the findings on single weather values such as tempera-
ture or atmospheric pressure and day-to-day changes of
these values probably can be generalised. Finally, the
paper-and-pencil headache diary for 90 days involved
the possibility that patients reviewed previous answers.
However, the patients had to answer 67 questions every
day (excluding specific headache questions).
Considering this large number of questions, it seems
very unlikely that the patients reviewed prior answers
when filling in the diary.
Conclusion
The present study as well as previous studies show that
the influence of weather on headache and migraine is
small if not negligible. This questionable influence can
be unfavourable as well as favourable. Our results
underline the importance of studying the relation
between migraine and weather independently of
patients’ subjective perception. They also underline
that other factors such as menstruation or lifestyle trig-
ger headache or migraine more frequently, and that
these factors should be main targets of therapeutic
approach.
Acknowledgements
We thank Drs. Kadriye Aydinkoc, Andrea Bo
¨ttcher, Evelyne
Geuder, Kathi Hanslik, Natalie Hattinger, Julia
Holzhammer, Ludmila Zahlbruckner and Robert Zingerle
for their help in data acquisition and data processing.
Conflict of interest
CW has received honoraria and travel funding from
AstraZeneca, Linde Gas, Menarini and Pfizer. KZ has
received honraria and travel funding from Biogen-Idec,
Sanofi-Aventis and Serono. CWB has received honoraria
from AstraZeneca. All other authors declare that they have
no actual or potential competing financial interest.
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