Middle-ages adults are reporting more chronic pain symptoms than older generations

As people age, they tend to report more acute or chronic pain – a common sign of getting older.

Yet, in the United States, middle-aged adults are now reporting more pain than the elderly, according to a paper published in the Proceedings of the National Academy of Sciences (PNAS).

This paradoxical finding is confined to the two-thirds of the U.S. population without a four-year college degree, and happens because each generation of less-educated Americans is experiencing higher pain throughout their lives, the researchers said.

The study adds to the body of work of Anne Case and Sir Angus Deaton of Princeton University and Arthur Stone of the University of Southern California (USC), who have long studied morbidity and mortality around the world.

Using survey responses from more than 2.5 million adults, the trio compared the relationship between age and reported physical pain in the United States.

The findings have profound policy implications. Today’s less-educated elderly have experienced less pain throughout their lives than the less-educated middle-aged people of today, who will be tomorrow’s elderly.

This could put further strain on the health care system, and the treatment of pain is difficult and controversial – often linked to the opioid crisis, the researchers said.

“The connection between less-educated Americans and pain is shaped by a number of factors from income to social isolation to rising deaths of despair. It’s of great concern to us, as researchers, that it seems to be worsening,” said Case, the Alexander Stewart 1886 Professor of Economics and Public Affairs, Emeritus at the Princeton School of Public and International Affairs.

Case conducted the study with Deaton, who is the Dwight D. Eisenhower Professor of International Affairs, Emeritus, and Stone, a professor of psychology at USC.

The researchers used data from surveys conducted by Gallup, the U.S. Census Bureau, and the European Union.

Reports of pain were recorded between 2006 and 2018 among adults aged 25-79 in the U.S. and 20 other wealthy countries. The American data were confined to Black and White non-Hispanics.

A snapshot of ages at a single moment in time cannot distinguish the effects on pain of age from intergenerational trends over time, so Case, Deaton, and Stone looked at different birth cohorts born between 1930-90.

To do this, they used data from four U.S. surveys: the Gallup Health and Wellbeing Index, the Census Bureau’s National Health Interview Survey, the Department of Health and Human Services’ Medical Expenditure Panel Survey and the University of Michigan’s Health and Retirement Study.

In their first analysis, they found that men and women of all races worldwide report more pain as they age, a finding they expected.

In their second analysis – after controlling for education level – they found this to also be true for Americans with a bachelor’s degree. Only the two-thirds of the U.S. population without a college degree reported more pain in midlife.

“This seems to be an exclusively American phenomenon, as people in other rich countries do not report higher pain in midlife,” Case said.

Less-educated Americans also experience more pain as they age. However, because each birth cohort reports higher levels of pain throughout their adult life than the cohort before them, those in middle-age report more pain at any given age than their elders, who have had lower pain levels throughout their lives.

The rise in pain from cohort to cohort also signals increasing chronic intergenerational distress, which could be caused by a myriad of factors.

Less-educated people are experiencing more social isolation, more fragile home lives, less marriage, and more divorce, as well as stagnant wages and job loss.

They’ve also seen rising deaths of despair, from suicide, drug overdose, and alcoholic liver disease, according to past work by Case and Deaton.

Of course, there are possible caveats, the researchers point out. People could be reporting more minor pain than in the past, or due to their pain, they could also have lost their jobs or taken on jobs with less physical strain (and lower wages).

Obesity is also a chronic problem in America; with more weight comes more strain on the body.

The uptick in people going to college could also explain some of the cohort-by-cohort differences.

Still, the findings should signal to policymakers that less-educated Americans are experiencing more and more distress, that tomorrow’s elderly will see more pain than today’s elderly, and that the issue of pain – and its treatment – isn’t going away anytime soon.

“Pain undermines quality of life, and pain is getting worse for less-educated Americans,” Deaton said. “This not only makes their lives worse, but will pose long-term problems for a dysfunctional healthcare system that is not good at treating pain.”

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Pain is a common symptom which brings heavy burden to people’s life. It not only affects people’s overall health [1], but also seriously interferes with people’s daily activities, leading to depression, reduced social interaction and reduced quality of life [2]. There are many reasons and factors causing older adults’ status of pain, such as age, chronic disease status or unhealthy lifestyle. In the United States, the overall prevalence of pain is about 20.4% [3].

Among them, pain seems to have a greater impact on middle-aged and elderly people [4, 5]. It can be seen that with the progress of time and the aging of the global population, pain will become a more and more serious health problem.

In order to study the disease burden associated with non-fatal diseases, the Global Burden of Disease Research (GBD) used the concept of disability, which is defined as “any short-term or long-term health loss”, and proposed “Disability Adjustment Life Year (DALY)” and “Years Lived with Disability (YLD)” as calculation indexes [6].

Between 1990 and 2010, among the 10 major causes of YLD, there were 5 diseases characterized by pain. In the global burden of disease study in 2016 [7], among the 5 major causes of YLD, low back pain and migraine ranked first and second place.

Alexander K. Smith etc. mentioned in the study that in the last two years of life, the incidence of pain increased dramatically from 26 to 46% [8], regardless of the cause of death. Thus, pain can cause a lot of additional medical costs and economic losses over time, the burden of pain cannot be ignored.

China is a large country, with a population of over 1.3 billion. Over the past few decades, China has experienced tremendous development, including urbanization, income growth and aging, leading to a rapid increase in non-communicable diseases and a shift to chronic disability [9, 10].

In 2010, 25.3% of the population comprised individuals age 50 years or older in China [11]. Numerous studies have discussed the prevalence and economic burden of chronic pain in developed western nations, but for Chinese population, there are not many studies focusing on this area, most studies are about the mechanism and the treatment measures of pain. Studies have reported that rates of chronic pain in Chongqing appear to approximate to those reported in western countries [12].

A cross sectional study estimated the prevalence of pain and identify risk factors of pain among 19,665 community residents in China and found that Women had a higher prevalence of pain than men (39.9% vs. 32.2% for chronic pain) [13]. A cross-sectional study among 6524 elderly individuals aged ≥60 years in China reported the prevalence of chronic pain was 49.8%.

The legs/feet (25.5%), back (23.2%), and neck/shoulder (14.6%) were the most salient locations for chronic pain, subjects with overweight and obesity were more likely to have chronic pain [14].

However, high quality data regarding the prevalence of pain and its health economic burden in China based on a large sample size is still needed [15]. Using data collected from the China Health and Retirement Longitudinal Study (CHARLS), a national random sample of the Chinese population, we estimated the prevalence of pain among residents age 45 years or older in China in the year 2011, 2013 and 2015 through this nationwide representative sample of the follow-up survey on health and pension. Also, we analyzed the effect factors for pain, and calculated the direct medical costs for all types of pain by using the optimized two-part estimation method.

Discussion
Using data collected from the CHARLS, a national population survey, we observed that pain symptoms was common among Chinese adults, especially among those with lower socioeconomic status.

There was remarkable variation in the prevalence of pain according to socioeconomic status. Subjects with older age, female, low weight, lower education level, rural residents, no insurance and abstained from alcohol seems to have much higher prevalence.

The prevalence of pain in our study was significantly higher than that in Japan (17.5%) [18], France (20.2%) [19], the United States (20.4%) [3] and other countries [1, 3, 18,19,20]. In a systematic review, the prevalence of pain ranged from 0 to 24.0%worldwide [21].

A report from China National Committee on Ageing have shown approximately 30.9% of the urban older adults and 38.7% of the rural older adults were reported to have pain [22], which are quite close to our analysis in this study.

The high prevalence of pain in this study may be related to the following two reasons. First of all, the age of the population in our study was ≥45, while older age was a related risk factor for pain [23,24,25,26], the U.S. and France studied the whole population, while Germany was the population over 14 years old.

Secondly, the relatively low economic level of the population investigated in this study may also be one of the reasons. Low income was considered as a risk factor for pain in some studies [25]. A multivariate analysis of pain-related factors was conducted showing that there was a correlation between economic conditions and pain intensity as well as the consequences of pain.

In this study, the proportion of rural residents accounted for the majority, which may lead to inaccuracy of our estimation.

From the results of our study, we can tell the proportion of pain caused by musculoskeletal diseases is the highest, in which low back pain take the first seat in all parts of the body. Leg, knee, head, shoulder, and arm are the common pain areas with a prevalence of more than 10%. Except for the head, other part all belong to the musculoskeletal system.

In the global burden of disease study in 2016, low back pain ranked first among the five major causes of YLD [7]. It can be seen that the high prevalence of low back pain is one of the reasons for its high health burden. Some studies have shown that the prevalence of low back pain in adults ranges from 14.7 to 23.6% [26,27,28], which is consistent with our results. It can be seen that musculoskeletal diseases play an important role in both pain and YLD, which need to be paid more attention to.

Our study suggest that older age and female are independent risk factors for pain, which is consistent with some previous research results. A study of Swedish residents showed that the prevalence of chronic musculoskeletal pain increased with aging, and reached the highest between the ages of 59 and 74 [23]. In our study, the highest prevalence of pain was found in the age group of 65–74, which is close to the results of the previous study [29, 30].

Aging showed a positive correlation with increased incidence of cancer, osteoarthritis, spinal diseases, surgical injuries and other diseases, which may lead to pain prevalence [31]. Studies have found that the prevalence of pain, and musculoskeletal diseases in women was higher than that in men [14, 32].

One of the most common opinions on gender differences in pain is that women are more sensitive to pain. An electrical stimulation study found that the amplitude of female evoked potential was higher than that of male [33]. Hormones may play a role [34]. In addition, some scholars believe that gender differences in pain are related to psychological factors. For example, men are more reluctant to report pain than women [35].

In addition to demographic characteristics, we also studied the relationship between social structure and pain. Combining the results of univariate and multivariate analysis. We found a negative correlation between education and pain, which is consistent with some studies [36, 37], suggesting that higher education level may accomplished by higher pain endurance.

In this study, we also found that the prevalence of pain among rural residents is higher, which is consistent with the results of the study on farmers in Latin America and women in Tibet [38, 39], subjects live in rural areas and, with lower education level seem to report their pain more easily. In terms of medical insurance, we found that the prevalence of pain in uninsured people is higher.

People with low back pain in the United States had lower insurance coverage and were more likely to receive medical assistance [40]. The impact on pain may come from many aspects, such as the difficulty of access to health resources (including health-related education resources), medical concept and preference.

In addition, the impact of different occupations is tremendous, some occupations may be more vulnerable to the threat of pain, especially manual workers. For example, the prevalence of low back pain in Chinese garment workers (74%) was significantly higher than that in teachers (40%) [41].

It is generally believed that manual workers may be more threatened by pain. However, low education level, rural residents usually engage in more manual labor, and manual workers have lower coverage of health insurance. Documents have proved that physical intensive work, represented by agriculture, is more common in rural areas than in urban areas [42].

In our country, there are more rural residents, and according to the CHARLS baseline study report, many rural residents in our country do not stop working until 65 years old, and at least 20% of people over 80 years old are still working. Therefore, pain should be paid more attention in our country.

In terms of health behavior, we found that abstinence from alcohol and low BMI may be independent risk factors for pain, while smoking is not, which differs from previous studies [43,44,45], different set of cut-points for BMI didn’t influence this result. The relationship between smoking and pain may be considered in two ways.

On the one hand, a large number of studies have shown that smoking increases the incidence of pain in certain parts [43,44,45]. On the other hand, smoking may improve people’s bad mood, and the subjective factors of pain symptoms are strong, so smokers may tend not to report pain. Studies showed that nicotine can stimulate the release of dopamine to produce a relaxing and pleasant subjective experience, and nicotine also has an acute analgesic effect [46, 47].

Perhaps it is for these two reasons that we did not find a correlation between smoking and pain in our study. In terms of alcohol consumption, our conclusions differ from those commonly believed that alcohol consumption may lead to a higher incidence of pain. However, previous studies have shown that abstainers have a higher incidence of pain.

For example, the prevalence of migraine tended to decrease with the increase of alcohol consumption compared with abstinence, and explained it as the deposition characteristics of alcohol [48]. In addition, the prevalence of pain among abstainers is higher, probably because many abstainers are passively abstaining from alcohol because of some illnesses, which in turn have painful symptoms.

The relationship between low BMI and pain may be related to some diseases, and malnutrition is a risk factor for some chronic non-communicable diseases. Barbara et al. studied whether nutritional risk was associated with chronic musculoskeletal pain in the elderly living in the community by scales.

The results showed that nutritional risk score was independently associated with chronic musculoskeletal pain. For each additional unit of risk score, the risk of pain increased by 11% [49].

Pain will cause more additional medical costs. According to the data of the National Bureau of Statistics, in 2011, 2013 and 2015, the total population of China was 1347.35 million, 1360.72 million and 1374.62 million [50]. It can be estimated that the economic losses caused by pain in China in 2011, 2013 and 2015 are 352.99–613.77 billion yuan, 1051.94–1327.29 billion yuan and 959.02–1439.45 billion yuan (converted to 2010 RMB), respectively.

The cost of pain-related medical care in the United States in 2010 was $261 billion to $300 billion [51], which was 1728.52–1986.81 billion yuan. Generally speaking, although the additional direct medical cost caused by pain in China may be lower than that in some developed countries such as the United States, it will still cause greater economic losses.

The innovation of this study is to design two models to calculate the approximate range of additional direct medical costs caused by pain. Model 1 included fewer confounding factors, only the most important demographic characteristics and individual family competence characteristics.

Therefore, the additional direct medical costs caused by pain may be underestimated. Health needs and health behaviors were incorporated in model 2, which may have a positive impact on the direct medical costs through pain. Therefore, when these factors are included as confounding factors, the additional direct medical costs of pain calculated by model 2 may be overestimated. In this way, we can estimate the range of additional direct medical costs caused by pain through the two models.

There’re also several limitations in our study. Firstly, the main disadvantage is the high missing value in the process of data screening, especially in 2013, which may lead to a certain selection bias, resulting in a decline in the credibility of the results. Secondly, this study lacks a specific scale for the collection of pain data, which is strongly effected by the subjectivity of the respondents.

Thirdly, this study does not include the calculation of indirect medical costs caused by pain, so the estimation of economic burden caused by pain is conservative. Fourthly, the financial burden of pain may still be underestimated. On the one hand, we only include people aged 45 and over, but not under 45.

On the other hand, our study did not calculate the additional indirect medical costs associated with pain, such as the cost of missed work, the cost of hiring a nanny, etc. However, due to less research on pain-induced economic burden and lack of overall data, the result in this paper is still irreplaceable and necessary. Further research is needed to start with different severity of pain and different types of medical costs, focusing on the collection of relevant data for deeper longitudinal research.

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Source: Princeton