We obtained the population, prevalence, incidence, and age-standardized rates (ASR) data for all age and age-standardized groups across the BRICS from GBD 2019. This dataset is accessible at http://ghdx.healthdata.org/gbd-results-tool (accessed on 2023-06-07). The GBD 2019 amassed information relevant to 369 diseases and injuries and scrutinized 87 associated risk factors spanning 204 countries and territories (13). We conducted our study in strict adherence to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. Given its cross-sectional design, our study received ethical clearance from the Shanghai Ninth People’s Hospital. The board provided a waiver for informed consent, considering our exclusive focus on data analysis and the absence of personal identifying information.

The GBD aggregated data from a plethora of sources, encompassing censuses, surveys, vital statistics, and a myriad of health databases. To adeptly synthesize this extensive dataset, the GBD model utilizes three advanced methodologies: the Cause of Death Ensemble model, the spatiotemporal Gaussian process regression, and the Bayesian meta-regression tool, DisMod-MR 2.1 (14).

Within the GBD 2019 cause hierarchy, headache disorders are classified at Level 3, nested under neurological disorders at Level 2 and non-communicable diseases at Level 1. Under Level 4, headache disorders are further differentiated into migraine and TTH, with no subsequent subdivisions (15). A migraine is a primary headache disorder often characterized by recurrent moderate or severe unilateral pulsatile headaches. The International Classification of Headache Disorders, 3rd edition (ICHD-3) provides definitive diagnostic criteria for migraines. If a patient’s symptoms fulfill all five of these major diagnostic criteria, they are diagnosed with a definite migraine (6, 16). However, any headache that meets all but one of these criteria is termed a probable migraine. TTH manifests as a dull, non-pulsatile, diffuse, band-like or vice-like pain, ranging from mild to moderate intensity, usually located in the head or neck. The diagnostic procedure for TTH mirrors that of migraines. Following the ICHD-3, a definite TTH diagnosis is given if a patient’s symptoms align with all five major criteria, while a probable TTH aligns with all but one criterion (6, 16). In our study, we utilized codes from the International Classification of Diseases, 10th revision (ICD-10), specifically G43-G43.919, G44.2-G44.229, and G44.4-G44.41, to denote migraines and TTH (6, 16).

In this study, we examined the repercussions of migraines and TTH on health outcomes. To quantify the extent of these effects, we utilized various metrics such as incidence, prevalence, DALYs, along with their corresponding rates. DALYs, encompassing years of life lost to premature mortality and years lived with disability, serve as a pivotal metric in gaging disease burden and overseeing public health (17). In this study, the disease burden was articulated with 95% uncertainty intervals (UI). For a detailed understanding of the adopted methodology, we refer readers to the relevant literature (6, 14). Given the heterogeneity in age distributions and populations within the GBD dataset, adjusting for disparities in age structures becomes paramount. Utilizing the age-standardized incidence rate (ASIR), age-standardized prevalence rate (ASPR), and age-standardized DALYs rate enhances the comparability across populations with varying age structures and demographic sizes (18). To quantify the trends in ASRs, we employed the estimated annual percentage change (EAPC) (19). A linear regression model was applied to the natural logarithm of the ASRs, represented as y = α + β x + ε with y being the ln(ASRs) and x indicating the calendar year. The EAPC was determined as 100 × (e^β − 1), with its 95% confidence interval (CI) derived from the linear regression model (20). The trajectory of the ASR can be elucidated by examining the EAPC in conjunction with its 95% CI. An upward trend in the ASR is inferred when both the EAPC and the lower boundary of its 95% CI exceed zero. On the other hand, a downward trend in the ASR is indicated when both the EAPC and the upper boundary of its 95% CI fall below zero (20). To project the disease burden from 1990 to 2045, we employed a log-linear age-period-cohort model. We harnessed the NORDPRED software package, developed and implemented in the R programming language, which has demonstrated empirical effectiveness in forecasting future trends (21). The extrapolation process entailed extending the data from the three or four most recent 5-year observed periods (subject to data availability). This extension was achieved using a power function designed to stabilize growth. Specifically, the projection featured a linear trend for the final 10 years, but this trend was dampened by 25% in the second prediction period, 50% in the third prediction period, and 75% in both the fourth and fifth prediction periods. The projections were conducted at 5-year intervals (22). In our investigation, we conducted analyzes and generated graphical representations utilizing the R statistical software, specifically, version 4.2.2. A threshold of 0.05 for the two-tailed p-value was employed to establish statistical significance.

As of 2019, Brazil maintained the highest migraine ASPR with 18,331 per 100,000 individuals (Table 1; Figure 1; Supplementary Figure S1A). This represents a notable augmentation of 4.48% since 1990, with an EAPC of 0.19 (95% CI: 0.13 to 0.25) (Table 1; Supplementary Figure S2A). Contrarily, China manifested the lowest ASPR, at 11,654.58 per 100,000 in 2019, marking an 8.1% increase since 1990 (Table 1; Figure 1; Supplementary Figure S1A). Significantly, India’s migraine ASPR saw a minute elevation of 0.02%, marginally shifting from 14,730.88 per 100,000 in 1990 to 14,733.56 per 100,000 in 2019. Concurrently, South Africa documented a subtle decline of 0.51% from 1990 to 2019, transitioning from 13,010.09 to 12,943.04 cases per 100,000 (Table 1; Supplementary Figure S2A). The Russian Federation observed a slight reduction in migraine prevalence, registering a 0.26% decrease over this period (Table 1; Supplementary Figure S2A). In 1990 and 2019, the ASPR for migraine was higher in women than in men, with women reaching the greatest ASPR in the 40–44 age group (Figure 2A).

In BRICS countries, India shouldered the greatest TTH cases in both 1990 and 2019, with over 200 million estimated cases in 1990 rising sharply to over 374 million by 2019 (Table 2; Supplementary Figure S1B). The ASPR of India also remained similar at approximately 26,160 per 100,000 population between 1990 and 2019 (Table 2; Figure 3; Supplementary Figure S1B). On the other end of the spectrum, South Africa’s ASPR decreased slightly from 24,909 per 100,000 in 1990 to 24,907 per 100,000 in 2019 (Table 2; Figure 3). In China, prevalent cases rose substantially from 208 million to 282 million between 1990 and 2019. Over the same period, ASPR increased slightly from 17,515.14 (95% UI 15,462.06-19,823.37) to 18,423.96 (95% CI 16,133.74-20,802.27) per 100,000 (Table 2; Figure 3; Supplementary Figure S2B). The EAPC was 0.27 (95% CI 0.2–0.34) (Table 2; Supplementary Figure S2B). Russia displayed a slight decrease in prevalent cases from 50.9 million to 50.3 million, while ASPR underwent a small increase from 32,319.09 (95% UI 28,783.56-35,980.02) to 32,560.37 (95% UI 29,068.49-36,148.29) per 100,000 (Table 2; Figure 3; Supplementary Figures S1B, S2B). In contrast to migraine, TTH had a relatively equalized ASPR between genders, with the ASPR reaching a maximum in the 35–39 year age group (Figure 4A).

In an examination of the BRICS nations, India emerged with the most significant migraine incidence cases in 2019, with an estimated 17,931,771 cases (95% UI: 15,751,991-20,086,848) and an ASIR of 1,216.95 per 100,000 (Supplementary Figure S3A). Following closely, China reported the second-largest incidence, totaling approximately 12,939,765 cases (95% UI: 11,463,449-14,485,073), albeit with the lowest ASIR at 961.69 per 100,000 (Supplementary Figure S3A). Brazil registered the third-largest incidence with about 3,023,237 million cases, but displayed the highest ASIR at 1,489.15 per 100,000 (95% UI: 1,290.61-1,698.33). South Africa had the least incidence, accounting for 606,270 cases (95% UI: 529,331-680,997) (Supplementary Figure S3A). When contrasted with the 1990 estimates, Brazil manifested the most substantial upswing in migraine incidence, marked by an EAPC of 0.24 (95% CI: 0.15–0.32) (Supplementary Figure S4A). Conversely, both South Africa and India experienced a marginal downturn (Supplementary Figure S4A). The incidence in the Russian Federation remained comparatively unaltered during this period (as detailed in Table 1). The incidence of migraine in the BRICS is distributed in a “pyramid” pattern across all age groups. The incidence rate is higher in women than in men, with the highest prevalence in the 10–14 years age group (Figure 2B).

Within the BRICS cohort, India reported the most pronounced TTH incidence in 2019, approximating 136,792,785 cases (95% UI: 121,078,648-153,329,091), which corresponds to an ASIR of 9,575.36 per 100,000 population (95% UI: 8,517.77-10,684.57) (Supplementary Figure S3B). China followed with the second-largest incidence at about 101,281,419 cases (95% UI: 89,412,157-114,335,361) and an ASIR of 6,821.71 per 100,000 (Supplementary Figure S3B). Brazil’s data revealed the third-largest incidence with approximately 22,655,734 cases (95% UI: 20,135,894-25,429,457) and an ASIR of 10,201.74 per 100,000 (95% UI: 9,009.4-11,437.75) (Supplementary Figure S3B). Notably, while the Russian Federation exhibited the highest ASIR, 11,512.04 per 100,000 (95% UI: 10,205.5-12,898.54), China presented the lowest at 6,821.71 (95% UI: 6,040.1-7,655.16). Comparative data from 1990 indicate that China experienced the most significant escalation in TTH incidence, marked by an EAPC of 0.19 (95% CI: 0.14–0.24) (Supplementary Figure S4B). Brazil also exhibited a growth trend (Supplementary Figure S4B). In contrast, incidence patterns in India and South Africa remained largely consistent throughout this period (as illustrated in Table 2). The incidence of TTH reaches its maximum in the age group 70–74 years and minimum in the age group 5–9 years (Figure 4B).

As delineated in Table 1 and Supplementary Figure S5, India demonstrated the highest migraine-associated DALYs, registering 7687692.52 (95% UI: 937248.14–17514317.34). In contrast, South Africa reported the minimal count, documenting 279238.11 (95% UI: 48,355.51-615,375.35). On assessing the DALY rate per 100,000 population, Brazil emerged at the pinnacle with 674.12 (95% UI: 71.77–1,605.15), while China presented the lowest rate, at 435.42 (95% UI: 63.68–991.8) (Figure 1). Notably, China and Brazil experienced pronounced escalations in age-standardized DALY rates. Conversely, India evidenced the most substantial reductions (Table 1). From 1990 to 2019, the DALYs rate for migraine was higher for women than for men, reaching a maximum at ages 40–44 (Figure 2C). Turning to Table 2, India again recorded the highest tally of TTH-associated DALYs, amounting to 741,392.13 (95% UI: 206,386.92-2,795,445.49) (Supplementary Figure S5B), while South Africa posted the least at 33,651.1 (95% UI: 10,836.35-112,250.71) (Supplementary Figure S5B). In terms of DALY rate per 100,000 population, the Russian Federation led with 101.83 (95% UI: 36.66–291.95) (Figure 2). However, China depicted the most conservative rate of 43.26 (95% UI: 13.55–147.86) (Figure 2). Remarkably, both China and Brazil showcased upward trajectories in age-standardized DALY rates (Table 2). From 1990 to 2019, the DALYs Rate for TTH is higher for women than for men, reaching a maximum at ages 50–54 and gradually decreasing after ages 60–64 (Figure 4C).

In an effort to delineate the relative impacts of demographic expansion, the aging process, and shifts in epidemiological patterns on the changing landscape of migraine and TTH epidemiology over the last 30 years, we undertook a comprehensive decomposition analysis (23). Overall, significant increases in migraine and TTH prevalence have been observed in all BRICS countries (except Russia), but most notably in India and China, which have seen the largest increases in migraine and TTH prevalence over the past 30 years (Supplementary Figure S6; Tables 3, 4). Between 1990 and 2019, population growth led to a 91.07 and 62.06% increase in the burden of migraine prevalence in India and China, respectively, and a 95.1% increase in the burden of disease in Brazil (Table 3). Whereas population growth remains an important driver of migraine incidence, population aging is a protective factor for migraine incidence (Figure 5; Table 3). In terms of migraine DALYs, population growth is a driver of DALYs in most of the BRICS countries, whereas in the case of population aging it is an important driver of migraine DALYs in Russia, in China, population aging and epidemiological change play a role in migraine DALYs to a similar extent (17.9% VS 20%) (Supplementary Figure S7; Table 3). In TTH, population growth continues to play a major driving role in incidence, prevalence, and DALYs (Figure 5; Table 4; Supplementary Figures S6, S7). In addition, Epidemiological change plays a larger role in migraine and TTH in China compared to other BRICS countries (Tables 3, 4).

In Figures 6, 7, we present the anticipated trajectories of TTH prevalence and incidence within the BRICS nations. The data delineate a subtle augmentation in TTH prevalence and ASPR in India, whereas the trajectories in the remaining nations remain largely unchanged. The patterns observed for prevalence and ASIR exhibit congruence. Pertaining to migraine prevalence, India is projected to experience a modest rise in affected individuals, even as the ASPR demonstrates a successive decline. Conversely, Russia is anticipated to persist with its extant decremental trend, while China’s ASPR is forecasted to ascend. In the context of incidence, both the ASIR and the aggregate incidence cases in India are predicted to undergo a reduction. China’s ASIR is expected to witness a marked surge, Russia’s incidence cases are projected to diminish annually, and the ASIR in Russia is likely to maintain its current stability, as illustrated in Supplementary Figures S8, S9.

Our study primarily analyzed the trends associated with two main types of headaches: migraines and TTH, leaving out trends for other headache disorders. It’s pivotal to emphasize that the foundation of our research is based on the GBD studies, which do not derive from primary data sources. This is particularly concerning as many countries, especially those in the Global South and certain conflict-ridden African nations, lean heavily on unverified estimates due to challenges they face in resources, expertise, and infrastructure essential for exhaustive headache epidemiology on a large scale. Such a dependence might infuse our results with biases and potential inaccuracies. Further complicating the issue is the fact that diagnostic criteria for migraines and TTH can differ, potentially leading to inconsistent incidence rates. These disparities might be magnified by cultural, regional, and methodological differences, with regional and cultural interpretations affecting the consistency in case identification. It’s worth noting that the evident surge in headache burden since the early 1990s might be influenced by improvements in diagnosis and heightened public awareness, factors our study does not distinctly account for. Without dedicated research dissecting this influence, our conclusions could be somewhat skewed. Even though we have endeavored to harmonize methodological differences across various studies, it’s pertinent to mention that some of the variations we observed might arise from measurement errors or intrinsic methodological biases, as opposed to genuine differences.