Published online June 1, 2006
PEDIATRICS Vol. 117 No. 6 June 2006, pp. e1197-e1201 (doi:10.1542/peds.2005-2274)
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Long-term Trends in the Incidence of Headache in Finnish Schoolchildren

Pirjo Anttila, MD, PhDa, Liisa Metsähonkala, MD, PhDb and Matti Sillanpää, MD, PhDb,c

a Child and Adolescent Health Care Unit, Turku City Hospital, Turku, Finland
b Department of Child Neurology, University Central Hospital of Turku, Turku, Finland
c Department of Public Health, University of Turku, Turku, Finland


   ABSTRACT
TOP
 ABSTRACT
METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES
 
OBJECTIVE. To study changes over time in the incidence of migraine and frequent headache.

METHODS. A population-based study on migraine and other headaches in Finnish children starting school at age 7 years in the city of Turku was conducted in 1974, 1992, and 2002. The study design used in each study was virtually identical. The study population included 1927 children in 1974, 1436 children in 1992, and 1066 children in 2002. The corresponding response rates were 90%, 96%, and 81%.

RESULTS. An increasing trend in the incidence of migraine was found from 1974 to 2002 in both boys and girls. The incidence rates of migraine with aura increased from 5.2 per 1000 person-years in 1974 to 41.3 per 1000 person-years in 2002. The increase in the rates of migraine without aura was from 14.5 per 1000 person-years in 1974 to 91.9 in 2002. Similarly, a significant increase over time was seen in the incidence of frequent headache from 1974 to 2002 in both boys and girls.

CONCLUSIONS. The incidence of childhood migraine and frequent headache has substantially increased over the last 30 years. The increased incidence is alarming and reflects untoward changes in children's lifestyles. Additional studies are needed on causal associations with life changes.

Key Words: childhood headache • migraine • incidence • long-term trends

Abbreviations: ICHD—International Classification of Headache Disorders

Adult medically diagnosed migraine increased over time in the United States in the 1980s.1–3 Stang et al2 found a striking increase from 1979 to 1981 in the age-adjusted incidence of clinically diagnosed migraine in patients <45 years of age. Rozen et al3 studied the population of a defined geographic area, analyzing those who had sought medical aid for headache from 1979 to 1981 and from 1989 to 1990. They found an increased incidence of migraine in all age groups and particularly among those aged 10–45 years. In the 1990s, the prevalence of adult migraine has remained stable in the United States.4

To our knowledge, no population-based data have been published on long-term time trends in the incidence of primary headache and migraine in young children. We reported previously a significantly higher prevalence of headache in 1992 than in 1974 in 7-year-old Finnish schoolchildren.5 Our current hypothesis was that an increasing trend in the incidence of headache has continued. Our objective was to investigate whether the incidence of migraine and frequent headache had increased in Finnish schoolchildren from 1992 to 2002.


   METHODS
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 ABSTRACT
 METHODS
RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES
 
The present study was particularly designed to examine long-term time trends in the incidence of overall primary headache and migraine. The study was conducted in the City of Turku (total population: 175000 including ~30000 children aged <16 years).

In 1974, a baseline study evaluated all of the children starting compulsory school in Turku. The study population included 1927 (90%) of 2134 schoolchildren who were 7 years of age meeting the following inclusion criteria: Finnish as mother tongue, no mental retardation, resident in Turku, and living in childhood home. Excluded were children whose language was something other than Finnish, residents of municipalities other than Turku, and institutionalized children. At the beginning of the school year, all of the children underwent a routine clinical assessment of health status lasting ~30 minutes by his or her school doctor in the presence of 1 or the both parents. With the assistance of the parent or parents, the children completed a structured headache questionnaire, which was immediately checked by the doctor for any incomplete or misunderstood items. The variables included in the questionnaire have been described previously.5

In 1992, the study was repeated, with an almost identical design, covering the same geographic study area, the same 39 schools (except for 2 schools which, for administrative reasons, had been annexed to neighboring schools), the same design of medical examination, and partly the same doctors and school nurses as in 1974. The layout of the questionnaire was a photocopy of the previous one. A total of 1436 (96%) 7-year-old children participated in the 1992 study. The study design and results of the 1974 and 1992 studies have been reported in detail previously.5,6

In 2002, the study was again repeated, with the same identical study design as in 1974 and 1992, including the same schools, age group, time of year, and data collection method. Recruited were 1066 schoolchildren aged 7 years or 81% of the eligible children. Excluded children mainly consisted of ones whose native language was not Finnish. No significant age or gender difference was found between participants and nonparticipants. Of the 1066 participants, 525 (49%) were boys, and 541 (51%) were girls. Neither age nor gender distribution showed any significant differences between the 3 surveys. Therefore, no age or gender adjustment was made. The primary reason for the decrease in the number of children participating in the 3 surveys was a decrease in the birth rate in Turku from 1974 to 2002. Of the child population, 98% in 1974, 98% in 1992, and 94% in 2002 was eligible.

Incidence rates were new cases per 1000 person-years. New cases included children who had a headache during the preceding 6 months but not before that. The incidence rates per 1000 person-years were calculated from new cases of headache during the preceding 6 months before the study in 1974, 1992, and 2002, respectively. A 6-month observation period was chosen to minimize recall bias.

In all 3 of the surveys, the definition of migraine was based on Vahlquist's criteria.7 These criteria for migraine include recurrent, paroxysmal headache attacks separated by symptom-free intervals with ≥2 of the following 4 features: unilaterality, nausea and/or vomiting, visual or other aura, or family history of migraine. Headache during the preceding 6 months and earlier and age at onset of headache was documented. Frequent headache was defined as headache episodes occurring at least once a month. In 1988, the International Headache Society published the International Classification of Headache Disorders (ICHD) criteria for making headache diagnoses (ICHD-I).8 We reported our 2002 findings also using the second revised edition of the ICHD (ICHD-II).9

Statistical Analysis
The descriptive values of variables were expressed as frequencies and percentages. Between categorical variables, univariate associations were analyzed using cross-tabulation. The statistical significances of these associations were analyzed using Pearson's {chi}2 test with Fisher's exact test (2-tailed) when appropriate. The Cochran-Armitage trend test was used for time trends. The Wilcoxon test was used for age differences at the onset of migraine from 1974 to 1992 and from 1992 to 2002. Poisson regression was used to calculate incidence rates per 1000 person-years, to compare incidence rates between the study years (1974, 1992, and 2002), and to investigate any trends over the study years. A P < .05 was used as the cutoff point of significance. The statistical analyses were conducted using SAS system software, version 9.1.3 (SAS Institute, Cary, NC).

Ethics
The study design was approved by the Joint Ethics Review Committee of the University of Turku Medical School and the Turku University Central Hospital.


   RESULTS
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 ABSTRACT
 METHODS
 RESULTS
DISCUSSION
 CONCLUSIONS
 REFERENCES
 
Table 1 shows the overall and gender-specific incidence rates of migraine in children in 1974, 1992, and 2002. The incidence rates of overall migraine, as well as migraine with or without aura, increased from 1974 to 1992 (P < .0001). The significant increase in incidence continued from 1992 to 2002 in both girls and boys. Similarly, the incidence rates of frequent headache increased from 1974 to 1992 (P < .0001), and the increase in incidence continued from 1992 to 2002 in both girls and boys (P < .0001; Table 2).


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  		TABLE 1 Incidence per 1000 Person-Years (95% CI) of Migraine in 7-Year-Old School Children in Finland

 

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  		TABLE 2 Incidence per 1000 Person-Years (95% CI) of Frequent Headache in 7-Year-Old Schoolchildren in Finland

 
Poisson regression analysis (Table 3) showed that the risk of frequent headache had more than doubled in 2002 compared with 1974 and was almost equally high in girls and boys. The risk for migraine with aura was threefold in 2002 compared with 1974. A significantly increasing long-term time trend was observed in the incidence of migraine across migraine types in both girls and boys. We also found a significantly increasing long-term time trend in the incidence of frequent headache in both girls and boys. Age at the onset of migraine proved earlier in the 2002 study than in the 1992 study (P < .001) or the 1974 study (P < .001; Fig 1), respectively, especially in boys.


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  		TABLE 3 Risk Ratios by Poisson Regression Analyses for the Increase in the Incidence of Headache in 7-Year-Old Children in Finland in 2002 Compared With 1974

 

Figure 1
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  		FIGURE 1 Cumulative incidence of migraine in 7-year-old Finnish children in 1974, 1992, and 2002.

 

   DISCUSSION
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 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
CONCLUSIONS
 REFERENCES
 
A clear-cut increase in the incidence over time of both frequent headache and migraine occurred in 7-year-old Finnish schoolchildren from the mid-1970s to 2002. The increase occurred both in girls and boys but seemed to begin earlier in boys than in girls. The results are based on a preplanned, prospective follow-up of time trends in unchanged circumstances. Notably, we could maintain the study design almost identical and comparable in all 3 substudies, and, subsequently, the methods of case finding and ascertainment were valid and reliable.

An increase in the incidence of migraine might result from increased disease awareness among children and their families or changes in migraine definition. In the present study, we identified migraine sufferers by assessing individual symptoms and applying diagnostic criteria. For consistent comparison, migraine was diagnosed using the same, well-known Vahlquist's criteria7 in 1974, 1992, and 2002. In the study by Metsahonkala and Sillanpaa,10 these criteria were less restrictive than the ICHD-I criteria.8 We reported our 2002 results also using the updated version of the ICHD criteria, ICHD-II,9 and reached similar conclusions. If we had chosen the ICHD-II criteria9 in 1974, 1992, and 2002, the incidence rates might be slightly lower, but an increasing trend in the incidence of migraine and frequent headache would be apparent. However, there may be different reporter bias. Headache is a socially acceptable symptom and, therefore, hardly underreported in 1974. One explanation might be that increased disease awareness for migraine in the 1990s, even in young children and their parents, could reduce the threshold for talking about and overreporting symptoms in the second and the third measurements. Even if this may happen, it could not entirely explain the increased incidence of migraine with or without aura.

In the mid-1980s, Stewart et al,11 using a telephone interview, studied the incidence of migraine with visual aura and found it to be 6.3 per 1000 person-years in girls and 5.6 in boys in 6–7-year-old children. The corresponding figures for 8–9-year-old girls were 10.4 per 1000 person-years and for boys of the same age 4.8 per 1000 person-years. Our incidence rates from the 1974 and the 1992 studies are consistent with those of Stewart et al.11 In another study from the United States, Rozen et al3 conducted a 2-phase, cross-sectional analysis of adolescents seeking medical aid for headache during the 3-year period of 1979–1981 and the 2-year period of 1989–1990. They found an increased incidence of clinically diagnosed migraine in girls aged 10–19 years, from 385.8 new cases per 100000 person-years in 1979–1981 to 647.9 new cases per 100000 person-years in 1989–1990. The incidence rates in boys aged 10–19 years increased from 196.8 new cases per 100000 person-years in 1979–1981 to 371.5 new cases per 100000 person-years in 1989–1990. In agreement with our results, they reported a clear increase in the incidence. The lower rates of the study of Rozen et al3 probably result from their different method of case identification, because their study included only those reporting clinically diagnosed migraine, and only a small proportion of children suffering from migraine in the community are known to seek medical attention.

Not only headache but also other pain modalities, such as abdominal pain, neck-shoulder pain, lower back pain, and toothache, have increased over time in Finnish children, especially after the mid-1990s.12–14 Santalahti et al12 found an increased prevalence of recurrent abdominal pain among 8-year-old children from 1989 to 1999. Hakala et al13 studied changes in neck-shoulder pain and back pain in 189894 Finnish adolescents between 1985 and 2001. They found the increase in the prevalence of weekly neck-shoulder pain in 16-year-old adolescents from 24% to 38% in girls and from 8% to 16% in boys and of weekly lower back pain from 8% to 13% in girls and from 7% to 11% in boys over the 1990s, especially after the mid-1990s. Honkala et al14 studied changes in toothache among Finnish adolescents from 1977 to 1997. In their Adolescent Health and Lifestyle Survey, a questionnaire was mailed to 12-, 14-, 16-, and 18-year-old adolescents. The study was composed of 35349 adolescents. The incidence of toothache during the previous 2 years was examined in 1977, 1985, 1991, 1995, and 1997. The prevalence of toothache decreased between 1977 and 1985 from 31% to 25%, was stable (28–29%) up to 1995, and after that significantly increased between 1995 and 1997 from 29% to 37%. The increase was highest in 16- and 18-year-old adolescents, but was already found in 12-year-olds.

Several reasons for the increase in headache in children may be put forward. One is a general trend of decreasing sleep.15 During the 1980s and 1990s, the duration of nighttime sleep has shortened and morning fatigue has increased in Finnish schoolchildren aged 11–15 years.16 Sleep deprivation may also provoke headache in young children.17

In the 1990s, increase in use of information technology18 and the subsequently increased hour-long daily sedentary position may further contribute to increased headache. At the end of the 1980s, computer use at home or school was rare, but at the beginning of the 2000s, 93% of adolescents used computers, 54% daily.18 According to our recent study,19 children with migraine or with tension-type headache used computers more than those without headache. We also found that 1 more day of computer usage in a week increased the odds of belonging to the migraine or tension-type headache groups by 20% and 30%, respectively, compared with children without headache.19 Headache can be caused by tense neck muscles as a result of recurrent, monotonous, and static working postures at a computer. In addition, the flashing lights of computers may provoke migraine in children.20 We did not ask how many of the 7-year-old schoolchildren were using computers. However, in a population-based study on computer game usage in young children, children >6 years of age played computer games 0.72 hours per day.21 Bener et al20 reported that playing on a computer was the most common type of environmental exposure associated with migraine in schoolchildren.

Soft drink consumption more than doubled among children and adolescents aged 6–17 years between 1977–1978 and 1994–1998.22 At the same time, we found more than a double risk of migraine or frequent headache among 7-year-old children in 2002 compared with 1974. Increased use of soft drinks may be related to recurrent headaches in children.23

Headache starts earlier now than in the 1970s, which probably partly explains the increasing time trends in headache occurrence. In the 1970s, children started to suffer from migraine at school age, whereas today many children already have had migraine attacks at preschool age. This may be partly associated with the current stressful lifestyle starting earlier than before or changes in the social environment.5 Our findings are alarming and certainly indicate a need for additional studies on the occurrence and causes of increasing pediatric headache.


   CONCLUSIONS
TOP
 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
REFERENCES
 
The incidence rates of migraine and frequent headache in 7-year-old Finnish schoolchildren increased from 1974 to 2002. The finding of the strikingly increasing trend presents a serious public health problem needing additional studies with other populations and causality analyses.


   ACKNOWLEDGMENTS
 
This study was supported by the city of Turku and the Foundation of the Turku University Central Hospital.


   FOOTNOTES
 
Accepted Dec 14, 2005.

Address correspondence to Pirjo Anttila, MD, PhD, Child and Adolescent Health Care Unit, Turku City Hospital, Linnankatu 28, FIN-20100 Turku, Finland. E-mail: pirjo.anttila{at}turku.fi

The authors have indicated they have no financial relationships relevant to this article to disclose.


   REFERENCES
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 ABSTRACT
 METHODS
 RESULTS
 DISCUSSION
 CONCLUSIONS
 REFERENCES
 

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  8. Headache Classification Committee of the International Headache Society. Classification and diagnostic criteria for headache disorders, cranial neuralgias and facial pain. Cephalalgia. 1988;8 :1 –96[Medline]
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  10. Metsahonkala L, Sillanpaa M. Migraine in children: an evaluation of IHS criteria. Cephalalgia. 1994;14 :285 –290[CrossRef][ISI][Medline]
  11. Stewart WF, Linet MS, Celentano DD, Van Natta M, Ziegler D. Age- and sex-specific incidence rates of migraine with and without visual aura. Am J Epidemiol. 1991;134 :1111 –1120[Abstract/Free Full Text]
  12. Santalahti P, Aromaa M, Sourander A, Helenius H, Piha J. Have there been changes in children's psychosomatic symptoms? A 10-year comparison from Finland. Pediatrics. 2005;115 :e434 –e442[Abstract/Free Full Text]
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  14. Honkala E, Honkala S, Rimpela A, Rimpela M. The trend and risk factors of perceived toothache among Finnish adolescents from 1977 to 1997. J Dent Res. 2001;80 :1823 –1827[Abstract/Free Full Text]
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PEDIATRICS (ISSN 1098-4275). ©2006 by the American Academy of Pediatrics




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