Introduction
Obesity is a major medical and public-health problem worldwide, affecting virtually all age and socioeconomic groups. Its prevalence is constantly increasing throughout the world [
1,
2], and it threatens to overwhelm both developed and developing countries. In China, obesity, defined as body mass index (BMI) ≥23.0 kg/m
2, affects almost half (44.6 %) of the adult population among adults age 40 years and above (men: 46.4 %; women: 43.6 %) [
3].
Migraine is also a major public-health problem worldwide, although less well recognized. In China, its prevalence in adults is 9.3 % (men: 5.9 %; women: 12.8 %) [
4], and it causes substantial illness and disability. Apart from their immediate impacts on well-being and ability to function, migraine and obesity are independent risk factors for cardiovascular disease [
5,
6], comorbid with pain-related and psychiatric conditions [
7‐
9] and lead to quality-of-life impairments [
10,
11]. These associations add to their importance as causes of public ill-health. There are, in addition, suggestions that obesity and migraine are themselves associated. Several (predominantly Caucasian) general population studies have shown an association between migraine and obesity in those of reproductive age [
12‐
15]. There were reports that obesity is associated with higher frequency and severity of headache attacks among individuals who have migraine [
16‐
18].
We investigated these associations in a recently completed large nationwide cross-sectional survey of the Chinese population [
4,
19], with the support of
Lifting The Burden: the Global Campaign against Headache [
20]. This was the first study evaluating the association between migraine and obesity in an Asian population. Through the comparison between Asia-Pacific population and Caucasian population, it helps for us to more thoroughly understand the association between obesity and migraine.
Results
Among the 5,041 survey participants, 12 with missing height or weight data were excluded, leaving 5,029 for the analysis [mean age: 43.6 ± 12.8 years; male 2,557 (mean age: 43.4 ± 12.9 years); female 2,472 (mean age 43.9 ± 12.8 years)]. Table
1 shows the distribution of demographic variables in the sample.
Table 1
Basic demographic data of the sample and migraine prevalence among different sub-groups
Gender |
Male | 2,557 | 50.8 | 152 (5.9 %) |
Female | 2,472 | 49.2 | 317 (12.8 %) |
Habitation |
Urban | 1,583 | 31.5 | 163 (10.3 %) |
Rural | 3,446 | 68.5 | 306 (8.9 %) |
Marital status |
Unmarried | 514 | 10.2 | 13 (2.5 %) |
Married | 4,342 | 86.3 | 438 (10.1 %) |
Divorced | 61 | 1.2 | 7 (11.5 %) |
Widowed | 112 | 2.2 | 11 (9.8 %) |
Educational level |
Illiterate | 406 | 8.1 | 47 (11.6 %) |
Primary school | 1,240 | 24.7 | 145 (11.7 %) |
Secondary school | 1,890 | 37.6 | 147 (7.8 %) |
High school | 953 | 19.0 | 82 (8.6 %) |
College | 540 | 10.7 | 48 (8.9 %) |
Occupation |
Unemployed | 428 | 8.5 | 40 (9.3 %) |
Farmer | 2,999 | 59.6 | 304 (10.1 %) |
Worker | 700 | 13.9 | 55 (7.9 %) |
Student | 129 | 2.6 | 4 (3.1 %) |
Officer | 654 | 13.0 | 61 (9.3 %) |
Other | 99 | 2.0 | 3 (3.0 %) |
Soldier | 20 | 0.4 | 2 (10.0 %) |
Age (years) |
18–29 | 847 | 16.8 | 27 (3.2 %) |
30–39 | 1,068 | 21.2 | 107 (10.0 %) |
40–49 | 1,301 | 25.9 | 154 (11.8 %) |
50–59 | 1,135 | 22.6 | 115 (10.1 %) |
60–65 | 678 | 13.5 | 66 (9.7 %) |
BMI categories are shown in Table
2, together with the estimated 1-year prevalence of migraine in each category. Overall, differences were significant (
χ2 = 14.661;
p = 0.005). Virtually all of this difference was accounted for by the morbidly obese category, with a highly significantly increased prevalence of migraine (16.8 ± 2.7 %) compared with the normal weight category (8.6 ± 0.6 %;
χ2 = 14.427,
p < 0.001; AOR = 2.095 [95 % CI 1.392–3.154],
p < 0.001).
Table 2
1 year migraine prevalence and adjusted odds ratios (AOR) for BMI categories
Normal | 2,469 | 212 (8.6 %) | Reference | |
Underweight | 262 | 27 (10.3 %) | 1.22 (0.80–1.87) | 0.359 |
Overweight | 1,064 | 100 (9.4 %) | 1.08 (0.84–1.39) | 0.541 |
Obese | 1,044 | 96 (9.2 %) | 1.04 (0.80–1.34) | 0.795 |
Morbidly obese | 190 | 32 (16.8 %) | 2.10 (1.39–3.15) | 0.000 |
Total | 5,029 | 467 (9.3 %) | | |
Severity, frequency and disability levels among different BMI categories showed no significant differences (Tables
3,
4,
5). It’s worth noting that participants in the underweight category tended more frequently to have severe migraine (47.8 ± 10.4 vs. 27.9 ± 3.7 %; AOR = 2.32 [0.94–5.75];
p = 0.070) and were more likely to be disabled (70.8 ± 9.3 % vs. 50.0 ± 3.8 %; AOR = 2.34 [0.92–5.97];
p = 0.075) than those of normal weight.
Table 3
Proportions with, and adjusted odds ratios (AOR) for, severe migraine (VAS ≥8) among different BMI categories
Normal | 41/147 (27.9 %) | Reference | |
Underweight | 11/23 (47.8 %) | 2.32 (0.94–5.75) | 0.070 |
Overweight | 20/82 (24.4 %) | 0.83 (0.44–1.57) | 0.569 |
Obese | 16/73 (21.9 %) | 0.72 (0.36–1.43) | 0.348 |
Morbidly obese | 8/25 (32.0 %) | 1.13 (0.45–2.86) | 0.793 |
Total | 96/350 (27.4 %) | | |
Table 4
Proportions with, and adjusted odds ratios (AOR) for, frequent migraine attacks (10–14 days/month) among different BMI categories
Normal | 10/121 (8.3 %) | Reference | |
Underweight | 0/13 (0.0 %) | 0.000 | 0.999 |
Overweight | 5/65 (7.7 %) | 1.03 (0.32–3.29) | 0.960 |
Obese | 8/53 (15.1 %) | 2.11 (0.74–5.98) | 0.161 |
Morbidly obese | 1/18 (5.6 %) | 0.64 (0.08–5.41) | 0.680 |
Total | 24/270 (8.9 %) | | |
Table 5
Proportions with, and adjusted odds ratios (AOR) for, disabling migraine (MIDAS grades II–IV) among different BMI categories
Normal | 87/174 (50.0 %) | Reference | |
Underweight | 17/24 (70.8 %) | 2.34 (0.92–5.97) | 0.075 |
Overweight | 46/89 (51.7 %) | 1.09 (0.65–1.82) | 0.751 |
Obese | 41/84 (48.8 %) | 0.98 (0.57–1.67) | 0.940 |
Morbidly obese | 14/27 (51.9 %) | 1.16 (0.51–2.65) | 0.718 |
Total | 205/398 (51.5 %) | | |
Discussion
First we emphasize the need, when analyzing and interpreting these data, to take into consideration the WHO body weight classification guideline specifically for the Asia-Pacific population [
24]. Doing this, we found a link between obesity and migraine prevalence rather than severity, frequency or disability. Morbidly obese respondents were twice as likely as those of normal weight to have migraine, the difference being highly significant. However, other BMI categories (underweight, overweight and obese) showed little relationship with prevalence. There were matching trends in the underweight to have migraine of greater severity and be more disabled.
The relationship between migraine and obesity was first evaluated in a clinic-based study, which found obese patients were three times as likely as age-matched normal-weight controls to have migraine [
25]. Ford et al. [
12] found that those who were underweight (BMI < 18.5) or obese (BMI ≥ 30) were at higher risk for having severe headaches or migraine compared with those of normal weight. Peterlin et al. [
13] found, in men and women aged 20–55 years, that higher migraine prevalence was associated with both total and abdominal obesity. And, this was the first study which suggested and clearly demonstrated that older individuals or those of post-reproductive age who have migraine do not have an association with obesity while those of reproductive age do, which also suggested that both obesity and migraine are modulated by reproductive status [
26,
27]. The finding that migraine and obesity are associated in those of reproductive age by Peterlin et al. [
13] was also later supported by data from Vo et al. [
15] and Robberstad et al. [
14]. Vo et al. [
15] found a significant association between migraine and obesity and that the odds of migraine increased with increasing obesity status. Robberstad et al. [
14] found that recurrent headache was associated with overweight (odds ratio [OR] = 1.4, 95 % CI 1.2–1.6,
p < 0.0001).
The role of race played in the association between migraine and obesity is not clear at present. In contrast to the Peterlin et al. [
13] study and Vo et al. [
15] study which were predominantly Caucasian population, our study has shown that there is an association between morbid obesity and migraine in a Asian population for the first time.
The reproductive status influence should be taken into consideration. While two studies done by Winter et al. [
28] and Mattsson [
29] evaluating populations of only post-reproductive age showed no association between migraine and obesity. Comparing with Peterlin et al. [
13] study, Mattsson [
29] study mainly focus on post-menopausal age group. Both reproductive age and post-menopausal age groups were included in our study, which might dilute our findings.
Bigal et al. [
16,
18] found that obesity, while not associated with increased prevalence of migraine, was related to frequent headache attacks (10–14 headache days/month), headache disability and likelihood of experiencing severe headache. Queiroz et al. [
30] found no significant relationship between migraine and BMI. Keith et al. [
31] found that obese women had increased risk of headache, but not specifically migraine. Téllez-Zenteno et al. [
32] found that there was no association between the disability and severity of migraine and BMI.
In conclusion, several general population group studies have shown a clear association between obesity and migraine in those of reproductive age group [
13‐
15]. In our study, we found migraine prevalence was significantly raised in the morbidly obese group, and this was a substantial and statistically significant increase. We also observed that there was a weak link between being underweight and migraine severity and disability.
Our study has several strengths. It was the first China nationwide study on headache of a population-based randomly selected sample, and was also the first migraine and obesity study in Asians, utilizing properly utilized measured BMIs. The sample was large (>5,000 respondents). Migraine was diagnosed by physician interviewers using a questionnaire based on the ICHD-II criteria. Anthropometric measurements were performed by the same interviewers, guaranteeing the accuracy of body height and weight information. While information on migraine severity and frequency depended, unavoidably, on subjective self-reporting by respondents, disability was estimated through the widely used MIDAS score [
23]. Furthermore, information about a large number of potential confounders was available, allowing us to make due adjustments in detecting any association between BMI and migraine.
Some limitations should also be considered. Despite our ability to control for a large number of potential confounders, we could not know of other comorbidities, including psychological, that might also be confounders, and we cannot exclude the possible influence of these since our study was observational. This study was also limited by the inclusion of post-reproductive aged individuals in light of the studies by Peterlin et al. [
13], Vo et al. [
15] and Robberstad et al. [
14]. In addition, our study was cross-sectional, not allowing us to determine any time sequence in the association between BMI and migraine. Otherwise, it is worth noting that the observation can be biased just because of the reduced sample size in the group of morbid obesity, and this should be taken into consideration while analyzing the results.
Although at present, there can be no definitive conclusion about the relationship between migraine and obesity, it is almost certain that the two are associated, in a probably complex way. The reasons for inconsistency in findings are not entirely clear. While we found, in the Chinese population, that morbid but not lesser degrees of obesity is associated with increased migraine prevalence but not severity, frequency or disability, studies of other populations have found evidence that obesity is associated with more frequent and severe migraine [
16‐
18] rather than an increased risk of having migraine. It may be that there are differences based on the culture or ethnicity. Certainly, any underlying mechanism linking migraine and obesity is not evident. Further population studies are needed to sort this out; whether or not a link exists is an important question both for its public-health implications and for better understanding the pathophysiology of these disorders.
Acknowledgments
This study was supported by Lifting The Burden: the Global Campaign against Headache, and by the Chinese Headache Society. Lifting The Burden is a UK-registered not-for-profit NGO. The paper was written without financial support by any pharmaceutical company or other agency. The authors are grateful for the arduous work of the neurologists, including Hua Bai, Min Chen, Xueying Guo, De’an Jiang, Weiqing Li, Jie Lin, Guohe Liu, Ying Liu, Minfang Lou, Xinming Lou, Yunwen Lou, Haidong Lv, Sha Ma, Haiyun Mei, Xia Shen, Jinping Sun, Ping Sun, Feng Tan, Mingshan Tang, Weiwen Wang, Lianhong Xie, Xionggen Xie, Jiangtao Xu, Jinsheng Yang, Wei Yang, Changjiang Yao, Lin Yin, Tao Yu, Huiying Zhang, Jintao Zhang, Yusen Zhou, Jianguo Zhu and Daliang Zou, and their teams, who took part in performing this nationwide survey.