This study sought to investigate the burden of MSK disorders in the USA, using data from the GBD dataset from 1990–2019. To the best of our knowledge, our investigation is the first study to attempt to quantify the burden of MSK disorders in the USA using the GBD dataset, and one of the first studies to comprehensively investigate MSK disorders in the USA from an epidemiological perspective. Overall, upon analysis of the GBD dataset, the burden of MSK disorders remains very high from 1990 to 2019 indicating the need for effective intervention to promote better health outcomes.
The GBD dataset reveals a higher prevalence in the majority of MSK conditions in the female population. 485,593 affected females to 187,234 affected males with RA. 13,272,059 affected females to 11,332,552 affected males with OA. 10,399,283 affected females to 6,980,885 affected males with neck pain. 15,803,242 affected females to 9,745,055 affected males with other MSK conditions. The exceptions being gout and lower back pain, which had higher prevalence in men. 1,904,810 affected males to 550,791 affected females with gout. 22,962,287 affected males to 20,276,752 affected females with lower back pain. A closer look at the disparities in gender observed in the GBD dataset indicates that the burden of MSK conditions has a larger impact on the female population. The reasons for which come down to a multitude of physiological, anatomical, and psychosocial factors.
Females more commonly suffer from migraines, a condition that is linked with a 12 times higher prevalence rate of neck pain [27]. Conditions such as polymyalgia rheumatica and fibromyalgia are also more prevalent in the female population. Both conditions are commonly associated with neck pain [28]. The increased oestrogen to androgen ratio in females promotes a proinflammatory state that is believed to contribute to the progression of rheumatoid arthritis [29]. The peak of oestrogen during pregnancy stimulates B cells and the Th2 response which results in the persistence of autoreactive B and T cell clones [29]. The decline in oestrogen during menopause results in the release of pro-inflammatory cytokines IL-6, IL-1β, TNF-α [29]. These events explain the high incidence of RA in females but particularly the increased incidence during pregnancy and menopause. Males have a higher articular cartilage thickness compared to females, which predisposes females to OA, particularly after menopause due to the lack of cartilage protective hormones [30]. Synovial fluid analysis in patients with OA reveals increased anti-inflammatory cytokines in males, and increased pro-inflammatory cytokines in females resulting in increased pain and inflammatory progression in females [31].
Recent studies into the effect of MSK conditions on the quality of life in female patients further elucidate the need for proper intervention to mitigate the burden of MSK conditions. It has been shown that RA has a negative impact on many aspects of sexual function including lubrication, orgasm, arousal, libido, and satisfaction [32, 33].
Despite being the highest contributor to DALY rates and numbers in 2019, low back pain is the only MSK condition that has decreased in burden, decreasing by 14.2%. A rather perplexing finding given that the number of people suffering from low back pain continues to increase over time. Low back pain prevalence globally has increased from 377.5 million in 1990 to 557 million in 2017 with a projected 843 million in the year 2050 [34, 35]. A potential explanation of this finding is that there is a great number of workers who underreport their pain and are less likely to call out of work to address their pain due to fear of job insecurity. A survey conducted by the Pew Research Center found that 73% of college educated Americans believe that there is currently less job security than 20–30 years ago [36]. Whether or not these claims are true, this illustrates a perception in the United States that job security is on the decline. Studies have shown that there is a significant association between job insecurity and not complaining of pain among younger people [37]. This trend could mask the true burden that low back pain has.
A closer look into the trends observed regarding age reveals an increase in the prevalence of MSK conditions in older populations from 1990 to 2019. With the highest DALYs seen in the age groups 65–69, 70–74, and 75–79. This trend can be explained in part by the growing population and prolonged life expectancy seen in the United States since 1990. The population has grown from 248.7 million to 336 million since 1990 to 2023, and the life expectancy has increased by approximately 5 years in that time period [38]. Overtime the understanding of these conditions has improved and patients are more frequently visiting their healthcare providers [39], which could result in higher incidences of MSK conditions being diagnosed.
Risk Factors
Cigarette smoking has experienced a decline in recent decades. The CDC reports that the number of cigarette smokers has decreased from 20.9–11.5% from 2005 to 2021. This decline in cigarette smoking mirrors the downward trend seen tobacco smoking age standardized DALYs contribution from 1990 to 2019, decreasing from 428.9 per 100,000 to 284 per 100,000. However, with the substantial harm cigarette smoking causes it is no surprise that it remains the largest risk factor for MSK disorders burden. Cigarette smoking has been shown to increase systemic inflammation and Matrix Metalloproteinase (MMP-12) [40]. MMP-12 is a macrophage elastase that has been implicated in the articular cartilage and joint destruction in RA [40]. This can exacerbate synovial inflammation in Rheumatoid arthritis by impacting the same mechanisms that are already impaired in the disorder. Synovial fluid in RA contains higher levels of MMP-12 [40]. RA also has been shown to have decreased expression of proapoptotic factors FOXO1, RB1, TP53, and BAX which reduces the susceptibility of cell lines to apoptosis and increases inflammation and joint destruction [41]. The mechanism of injury due to cigarette smoking as well as the altered mechanisms in RA serve to illustrate the potential for synergistic harm that still keeps smoking as the number one risk factor for MSK disorders burden despite its decline in usage over the recent decades. Further studies may see this downward trend revert back and rise as the popularity of vaping continues to soar.
Obesity has been a cause of growing global concern over the last few decades. In the United States the prevalence in obesity from 1994 to 2018 has increased from 23–43% [42].This substantial rise in obesity parallels the upward trend discussed earlier in the contribution of high BMI as a risk factor for MSK disorders increasing from 188 per 100,000 age standardized DALYs to 241 per 100,000. This trend can be attributed to the increased production of ultra processed foods, increased dependence on fast food services, and increased sedentary lifestyles over the recent decades. The NHANES survey shows that the American adult gets 57% of their energy intake from ultra processed foods [43]. With this continued rise in BMI, it is important to take a closer look into its impact on MSK disorders. Increased BMI has been shown to increase pain and stiffness via biomechanical stressors and promoting inflammation [44]. This not only increases pain and lowers quality of life, but it also increases the progression of the MSK disorder. Increased BMI has been shown to increase the progression of osteoarthritis and increase the risk for total arthroplasty of the hip [45]. It is no surprise that along with the aforementioned trends, we also see that the largest percentage rise for DALY rates and numbers was seen with gout. Jumping from 45.8% in 1990 to 66.7% in 2019. From 1990 to 2019 there has been an increase in the annual incidence of gout from 38.71 to 45.94 per 100,000 persons [46]. This rise in gout was observed in younger populations of varying socioeconomic backgrounds, with the largest rise seen in high income North American regions [46]. High BMI was found to be the greatest risk factor for years lived with disease for people with gout [46], further strengthening the link between the rise of obesity in the United States with the rise of gout. As the fastest growing risk factor for MSK disorders burden, it is imperative that swift and effective steps be taken to address the growing obesity rates in the United States.
Although there is a lack of definitive evidence to suggest that there has been a meaningful improvement in occupational policies to reduce MSK risks, more companies are becoming aware of the burden of MSK conditions and are exploring avenues to mitigate it. An example of such an endeavor can be seen in the Rolls Royce company where a study was conducted to determine the burden of MSK conditions on the company. It was found that 47% of the sick days accrued by employees within the study timeline were attributed to MSK conditions, costing the company £50 million [47]. These employees were also found more likely to require mental health referrals and more days needed away from work [47]. This substantial loss in financial costs and in employee productivity will hopefully drive Rolls Royce and other companies to take initiatives at reducing occupational related MSK risks. The US Buruea of Labor Statistics reports that health care and social assistance is the industry with the highest number of days away from work due to illness and injuries involving MSK disorders in 2018 with 56,360 days [48]. Followed by retail trade (41,070), manufacturing (38,640), transportation and warehousing (38,350) [48]. The financial impact on all these different industries is generating more awareness. Perhaps this growing awareness and focus on minimizing MSK risks in the workplace that is more apparent today than in previous decades explains the modest decline seen in the age standardized DALYs attributable to occupational risks from 1990 to 2019.
Public Health Implications
The findings of this study highlight critical public health implications, emphasizing the need for targeted interventions to address the identified challenges. The disproportionately high prevalence of MSK conditions in the female population underscores the importance of gender-specific interventions. Initiatives aimed at promoting awareness, early detection, and tailored treatment strategies for conditions such as rheumatoid arthritis, neck pain, migraines, polymyalgia rheumatica, and fibromyalgia could significantly improve outcomes for women [49]. Moreover, the paradoxical decrease in the burden of low back pain, despite its continued rise in prevalence, points to potential underreporting influenced by job insecurity perceptions. In this context, workplace-focused interventions, such as ergonomic improvements and mental health support, could mitigate the impact of job-related factors on the accurate reporting of MSK issues. Additionally, recognizing cigarette smoking and obesity as leading risk factors necessitates targeted public health campaigns to reduce smoking rates and address the growing obesity epidemic. These efforts can include anti-smoking initiatives, nutritional education, and initiatives promoting physical activity to alleviate biomechanical stressors and inflammation associated with MSK disorders. Furthermore, the study emphasizes the role of the workplace in MSK disorder prevention, exemplified by the Rolls Royce study [47]. Companies can implement measures like ergonomic workstations, health and wellness programs, and mental health support to reduce MSK-related sick days and enhance employee well-being. By focusing on these targeted interventions, public health initiatives can effectively address the multifaceted burden of MSK disorders in the United States.
Strengths and Limitations
Covering a span of three decades, our study provides invaluable insights into the long-term trends of musculoskeletal disorders in the U.S., highlighting changes and patterns that are crucial for understanding the evolution of these conditions. A key strength of our research lies in the use of the latest 2019 version of the GBD dataset, which has undergone significant enhancements in terms of data scope, quality, and comprehensiveness, especially in previously underrepresented regions. These improvements have enabled a more accurate and thorough analysis [19]. In terms of methodology, our study incorporates the latest scientific evidence and advanced disease classifications, along with refined uncertainty estimates, ensuring that our analysis is both current and robust. We have also taken a deep dive into various risk factors associated with musculoskeletal disorders, such as high BMI, kidney dysfunction, occupational ergonomic factors, and smoking. This not only aids in understanding the multifaceted nature of these disorders but also provides critical insights for potential preventive strategies. Furthermore, our research marks a pioneering effort in using the GBD 2019 data for an epidemiological analysis of musculoskeletal disorders in the United States, filling a significant gap in existing research. By providing quantifiable measures and thoroughly examining an understudied area, our study contributes valuable evidence-based directions for public health interventions and policymaking. Additionally, our findings underscore the urgent need for enhanced focus on rehabilitation medicine as a specialty in the US healthcare system, thus presenting a compelling call to action for healthcare providers and policymakers alike.
While our study offers significant insights into musculoskeletal disorders in the United States over three decades, it is important to recognize certain limitations. A primary limitation is the reliance on secondary data from the Global Burden of Disease study. Despite GBD's rigorous methods and estimations, secondary data can sometimes be less precise than primary data collection, potentially leading to inaccuracies or incomplete representations [50].
Particularly in the U.S. context, there might be disparities in data quality and availability, especially in certain demographic groups or specific geographic areas. This could result in potential errors or biases in our estimates, possibly leading to underestimation or overestimation of the true burden of musculoskeletal disorders. Additionally, while our study effectively identifies associations between various risk factors and musculoskeletal disorders, it does not establish causation. The ecological nature of the study means that our findings might be subject to ecological fallacies, and the lack of individual-level data restricts our capacity to make conclusive statements about individual risk.
Another limitation is the categorization of some musculoskeletal conditions. For example, different forms of low back pain, which can vary significantly in their etiology and clinical implications, were not always distinctly classified. This aggregation might have limited our ability to offer more precise findings and targeted intervention strategies [39]. We also recognize that there could be significant confounders and variables, such as lifestyle factors, comorbidities, access to healthcare, and treatment modalities, that interact with the DALYs associated with musculoskeletal disorders. Although these limitations are inherent to the GBD study methodology and were beyond our control, they must be acknowledged in the interpretation of our results.
Future Research
Future research should aim to build on the insights gained from the last three decades, while also exploring new methodologies and interdisciplinary approaches. One promising avenue is the expansion of comparative studies that juxtapose the trends observed in the U.S. with those in other regions globally. This comparative analysis could reveal region-specific factors influencing the prevalence and management of MSK disorders, offering a global perspective that could inform more effective prevention and treatment strategies. Additionally, there is a significant need to validate our findings through the utilization of diverse and expansive data sources. National health surveys, hospital records, insurance claims data, and longitudinal studies would not only corroborate the trends identified but also provide a more nuanced understanding of the progression and causation of MSK disorders. Such studies are particularly crucial in establishing definitive links between various risk factors, such as socioeconomic status, lifestyle choices, and genetic predispositions, and the incidence and severity of MSK disorders.
In the context of healthcare utilization and outcomes, future research must delve into how different treatment protocols and rehabilitation strategies impact patient outcomes in the U.S. This involves analyzing healthcare utilization patterns and their efficacy, offering insights into optimizing resource allocation and improving patient care. The role of technology, especially digital health solutions like telehealth and mobile health applications, should also be a focus area. These technologies have the potential to revolutionize the management of MSK disorders, particularly in a diverse and geographically vast country like the U.S. Furthermore, understanding the effectiveness of public health campaigns and prevention strategies in the U.S. could provide valuable lessons in reducing the burden of these disorders. Such research would benefit greatly from an interdisciplinary approach, integrating perspectives from epidemiology, genetics, public health, and health policy.