Introduction
The birth-cohort phenomenon of peptic ulcers (including duodenal and gastric ulcers) was first reported by Susser and Stein in 1962, [
1] and amended in 2002. [
2] They found that the mortality rates of gastric ulcers in England and Wales increased at the beginning of the 20
th century, reached a peak and then began to fall in the early 1950s. [
1,
2] They also found that the trends for duodenal ulcers were similar but followed approximately five years behind.[
1,
2] Susser and Stein hypothesized that each generation has carried its own particular risk of bearing ulcers throughout adult life and the fluctuations in the mortality rates of peptic ulcers represented a birth-cohort phenomenon.[
1,
2] Subsequent analyses from Western Europe, North America, and Asia have confirmed the presence of this cohort pattern.[
3,
4,
5,
6] Although 13 etiological theories have been proposed to explain the pathogenesis of peptic ulcers over the past 3 centuries,[
7] the mechanism underneath the birth-cohort phenomenon has never been fully understood.
In 1987, Marshall proposed that peptic ulcers are an infectious disease caused by the infection of
Helicobacter pylori (
H. pylori). As a result, currently peptic ulcers are widely believed to be an infectious disease caused by
H. pylori,[
8] but this etiology is controversial and how the bacterium leads to ulceration is unknown.[
9,
10,
11,
12,
13] The etiological theory of peptic ulcers based on
H. pylori infection was designated as
Theory of H. pylori.[
7] Unfortunately,
Theory of H. pylori cannot explain most of the 15 characteristics and 81 observations/phenomena of peptic ulcers,[
7] including 30 of the 36 observations/phenomena associated with the bacterium itself. Marshall himself could not explain the birth-cohort phenomenon of peptic ulcers.[
14] Starting from
Theory of H. pylori, Sonnenberg proposed a mathematical model to explain the birth-cohort phenomenon in 2006.[
15] However, this model overlooked the facts that the
H. pylori prevalence in gastric ulcers did not reach 50%,[
16,
17,
18] and 20-30% of duodenal ulcer patients could be
H. pylori-negative.[
13,
19] Moreover, this model failed to explain ‘the trends for duodenal ulcers were similar to gastric ulcers but followed ~5 years behind’, along with several other obvious defects.[
15] In addition, Sonnenberg’s explanation cannot be used to elucidate the other epidemiological mysteries on peptic ulcers, such as the seasonal variation[
20,
21] and African enigma,[
22,
23] as well as many other characteristics and observations/phenomena of the disease. Thus, the birth-cohort phenomenon of peptic ulcers has remained an unresolved mystery for 60 years.[
2,
14,
24,
25]
To address these challenges, a recently published Complex Causal Relationship (CCR)[
26] was applied to analyze the existing data, resulting in the birth of a new etiological theory,
Theory of Nodes.[
27,
28,
29] In this new theory, peptic ulcers were identified as a psychosomatic disease triggered by psychological stress, whereas
H. pylori plays a secondary role in only the late phase of peptic ulcerations.[
27,
28,
29] Encouragingly, this etiology explains all the 15 major characteristics and 81 observations/phenomena of peptic ulcers in a series of 6 articles (
Supplemental Table S1). In the first three articles of the series, 14 mahjor characteristics and 71 observations/phenomena of peptic ulcers, which have never been fully understood before, have been explicitly elucidated.[
27,
28,
29] This article is the fourth one, focusing exclusively on the 72
nd observation/phenomenon, the birth-cohort phenomenon of peptic ulcers. Since the fluctuation curves are the most important feature of this phenomenon,[
1,
2] this retroactive analysis will deliberate on elucidating the mechanism of the fluctuation curves. Despite two different diseases,[
25,
30] gastric and duodenal ulcers share similar mechanism of the birth-cohort phenomena. Thus, herein only the fluctuation curves of gastric ulcer are explored. In addition, how ‘the trends for duodenal ulcer are similar to gastric ulcer, but followed ~5 years behind’[
1,
2] is also elucidated.
1. Classification of the stressors causing peptic ulcers
In
Theory of Nodes, peptic ulcers are a psychosomatic disease triggered by psychological stress. In a specific region or population, there are always a proportion of individuals who are genetically predisposed to peptic ulcers, and due to past life experiences/ psychosomatic factors, many of them have developed hyperplasia and hypertrophy of gastrin and parietal cells in their stomach,[
28] or have formed a negative life view in their mind [
27]. Thus, this proportion of individuals is ready-to-ulcerate individuals and may become ulcer patients if psychological stress is induced for any reason. In that case, the mortality and morbidity rates of peptic ulcers are heavily impacted by stressors, including family, social, natural environmental factors and personality traits.[
28] Herein all the possible stressors in the literatures are classified into three categories according to their features (
Table 1). Clinical misdiagnosis occurs at a certain frequency,[
31,
32] but was more commonly seen in the early 20
th century because diagnostics were not as advanced as they are today. Misdiagnosis increases the overall mortality rate of gastric ulcer and affects the statistical results, thereby is regarded as the first category of stressors in this analysis. The second category is termed common events, which include everyday life and social events,[
33,
34,
35] struggling with personality disorders,[
36,
37] and social or natural environmental factors.[
38,
39,
40] Common events arise at a certain rate and thus cause relatively consistent mortality rates from year to year. For example, in a particular population, there are always a proportion of individuals facing divorce, unemployment, or conflicts with neighbours or family members. The third category is referred to as crucial events, which happen sporadically and last for an indeterminate amount of time, leading to an uneven mortality rate. For example, a war[
41] or an economic crisis[
42,
43] arises unpredictably, and is resolved in a period of time. Another example is natural disasters such as tsunamis or earthquakes,[
44,
45] which have short duration, but their effects may be felt long-term. All the three categories may cause their respective mortality rates of peptic ulcers.
Table 1.
Classification of Stressors.
Table 1.
Classification of Stressors.
Category |
Stressors |
Features |
Clinical Misdiagnosis |
1. Commonly seen in the 20th century. |
1. Occurs at a certain frequency. 2. Causes a relatively consistent mortality. 3. The mortality caused by misdiagnosis fluctuates slightly. |
Common Events |
1. Common social events: unemployment, divorce, poverty, family and neighbourhood conflicts, etc. 2. Struggling with personality disorders: immaturity, negative perception, hypochondriasis, dependency, impulsivity, etc. 3. Environment factors: seasonal alterations, working environment, urbanisation etc. |
1. Occur at a certain frequency. 2. Cause a relatively consistent mortality. 3. The mortality caused by common events fluctuates slightly. |
Crucial Events |
1. Wars: worldwide or local wars, massacres, religious conflicts, etc. 2. Crucial economic or social crises, political movements etc. 3. Natural disasters: earthquake, tsunamis, typhoon, flood, or landslides, etc. |
1. Happen sporadically and lasts for a limited period of time. 2. Leads to an uneven mortality rate. 3. The mortality caused by crucial events fluctuates markedly. |
8. The delayed occurrence of duodenal ulcers
Susser and Stein reported that the trends for duodenal ulcers were similar to gastric ulcers, but followed ~5 years behind in the birth-cohort phenomenon.[
1,
2]
Theory of H. pylori could not explain the delayed occurrence of duodenal ulcers.[
14,
15] In
Theory of Nodes, heredity, secondary stressors derived from crucial events, and the hyperplasia and hypertrophy of gastrin and parietal cells in the stomach, explained the delayed occurrence of duodenal ulcers in the birth-cohort phenomenon.
The importance of genetic factors in peptic ulcers has been emphasized by clinical observations.[
46] In
Theory of Nodes, individuals susceptible to gastric and duodenal ulcers belong to two genetically different populations.[
27,
28] As a result, although both populations experienced the same crucial events, the individuals with gastric ulcer predisposition may develop gastric ulcers, whereas the individuals with duodenal ulcer predisposition may develop duodenal ulcers. However, stressors for gastric ulcers, such as wars, unemployment, financial crisis, catastrophe, loss of family members, and divorce, which are usually short term and acute, directly cause gastric ulcers during or right after the crucial events. In contrast, duodenal ulcers are caused by the secondary stressors derived from crucial events, such as laborious work, poor work/living environments, lower social status, or strained family relations, which are usually long-term and chronic, cannot cause duodenal ulcers right away due to the chronic psychopathological process for the hypersecretion of duodenal ulcers. As a response to chronic stressors, it takes ~5 years to induce the hyperplasia and hypertrophy of gastrin and parietal cells in the stomach,[
47,
48] which in turn result in the hypersecretion of gastric acid and eventually, duodenal ulcers. On the other hand, unlike the easy-to-simulate acute stress that induces gastric ulcers,[
49,
50] the chronic stress that induces duodenal ulcer is difficult to duplicate in labs. Consequently, all stress-induced ulcers in animal models are gastric ulcers,[
46] further supporting the temporal differences between gastric and duodenal ulcers.[
27]
The fluctuation curves of duodenal ulcers in the birth-cohort phenomenon were dominated by the rise and fall of the mortality rates from the individuals who had a hereditary predisposition to duodenal ulcers and were impacted by the secondary stressors derived from crucial events. Thus, despite experiencing the same crucial events, a proportion of individuals developed gastric ulcers right away, causing increased mortality rates immediately, whereas another proportion of individuals developed duodenal ulcers ~5 years later. As a result, the trends for duodenal ulcer incidence were similar to gastric ulcers, but followed approximately five years behind in the birth-cohort phenomenon.
Discussion
Despite 13 etiological theories being proposed,[
7] the birth-cohort phenomenon of peptic ulcers has never been fully understood before since it was first reported in 1962. In contrast, guided by the CCR,
Theory of Nodes identified the etiology of peptic ulcers, and employed one of the CCR’s accompanying methodological concept,
Superposition Mechanism, to fully elucidate the underlying mechanism of this 60-year-old mystery.
Theory of Nodes attributed the success to a definite etiology with effective analytical methods, the
superposition mechanism.
Unequivocally, an etiological theory proposing the correct cause of peptic ulcers should be able to explain all the characteristics and observations/phenomena of the disease.[
7] However,
Theory of H. pylori cannot face the challenges of almost all the 15 characteristics and 81 observations/phenomena of peptic ulcers,[
7] indicating
H. pylori infection may not be the cause of peptic ulcers. Interestingly, herein
Theory of Nodes elucidated the birth-cohort phenomenon of peptic ulcers without taking
H. pylori into consideration, further suggesting that the infection of this bacterium is not the cause of the disease.[
28] Instead, ‘a causal relationship between
H. pylori and peptic ulcers’[
51,
52,
53] might be an illusion in medicine. Thus, it is not surprising that Marshall and Sonnenberg could not fully explain this phenomenon,[
14,
15] along with all the other 15 characteristics and 75 observations/phenomena of peptic ulcers.
In fact, the birth-cohort phenomenon reported by Susser and Stein in 1962 has implicated the true cause of peptic ulcers, as they speculated that stress caused by ‘the First World War and the unemployment in 1930s roughly fit the fluctuation curves’.[
1,
2] However, modern medical doctors rarely attribute the origin of a disease to the invisible, intangible, and incorporeal abstract stress. Instead, they get used to attribute the cause of disease to visible, tangible, and corporeal concrete essence (structural abnormalities) of the human body, such as gene mutations, infectious microbes or other aberrant biological molecules. As a result, Susser and Stein’s finding was not supported by the mainstream of etiological concepts in modern medicine for 60 years. In contrast, despite leading to many controversies,[
9,
10,
11,
12,
13]
H. pylori perfectly matched the etiological concepts of modern medicine and thus, the infection of the bacterium was widely believed to be the cause of peptic ulcers soon after the discovery in 1982.[
52,
54,
55] Consequently, the pathogenesis of peptic ulcers remains elusive for many decades.
Guided by the CCR,
Theory of Nodes identified that ‘peptic ulcers are not an infectious disease cause by
H. pylori infection, but a psychosomatic disease triggered by stress’.[
28] Starting from this etiology,
Theory of Nodes pinpointed the valuable historical data and classified all the possible causes of peptic ulcers into 3 categories, making a full understanding of the birth-cohort phenomenon possible. This etiology is also the key to fully elucidating 14 major characteristics and 71 observations/phenomena of peptic ulcers in the first three articles of the series (
Supplementary Table S2-S6)[
27,
28,
29]. Apparently, without the CCR, modern medical scientists do not have a benchmark to identify the cause of peptic ulcers, making almost all the 15 major characteristics and 81 observations/phenomena unresolved mysteries for centuries. Similarly, without the CCR, the etiologies of the vast majority of diseases remain unknown in modern medicine. The foregone result is that no disease can be fully understood, and most characteristics and observations/phenomena of any disease ‘remain unknown’ or ‘need more studies’[
28]. Therefore, a full understanding of the birth-cohort phenomenon of peptic ulcers implicates that the CCR should be widely applied to explore any life phenomenon and human disease.
The application of a new methodological concept,
superposition mechanism, is another key to fully elucidating the birth-cohort phenomenon. Even though
Psychosomatic Theory and
Stress Theory highlighted the driving roles of personality traits and/or social/natural events in 1950, the birth-cohort phenomenon of peptic ulcers has remained a mystery for 60 years, indicating that the correct etiology alone is far not enough to elucidate this phenomenon. The CCR dictates that the abstract essence is the driving force of any phenomena in the universe, and all the complex life phenomena and human diseases are driven by multiple abstract essences by
superposition mechanism. Reasoning backward from this mechanism suggests that the curves in the birth-cohort phenomena of peptic ulcers can be differentiated into multiple ‘annual mortality rates’, which can be further differentiated into the individual mortality rates caused by many single stressors, and an integration of these mortality rates should be able to reflect the epidemiological pattern of peptic ulcers, the birth-cohort phenomenon. Following this train of thought,
Theory of Nodes collected all the possible stressors from literatures, counted the annual mortality rates by all the individual stressors, and then superpose them to reproduce the fluctuation curves in the birth-cohort phenomenon. Hence, the
superposition mechanism originated from the CCR is indispensable to elucidate the birth-cohort phenomenon. Unfortunately, without the CCR, the concept ‘
superposition mechanism’ has never come into being before. As a result, even though
Psychosomatic Theory and
Stress Theory emphasized the important roles of personality traits and social events in peptic ulcers in 1950,[
7] the birth-cohort phenomenon still remained unexplained. Consequently, both theories could not be credited to have discovered the true cause of peptic ulcers in modern medicine.
Notable,
superposition mechanism can be widely applied to elucidate the mechanism of any phenomenon in the universe, especially for complex life phenomena and human diseases. In fact, the parallelogram law of forces in physics proposed in Newton’s second law in 1687[
56] has exemplified the application of
superposition mechanism. Modern medical research can be divided into an 8-level structural hierarchy: society, individual (the human body), system, organ, tissue, cell, organelle, and biomolecule. Interestingly, the
superposition mechanism can be applied to all the 8 levels, leading to ground-breaking insights of life phenomena and human diseases. In
Theory of Nodes,
superposition mechanism was flexibly applied 3 times to 3 different levels and thus, it fully elucidated all the 15 characteristics and 81 observations/phenomena of peptic ulcers within a series of 6 articles. The first application was to the organ level, where 5 etiological theories in history were superposed/integrated into one single theory to illustrate a complete pathological process of peptic ulcerations,[
28] thereby giving the birth to
Theory of Nodes. The second application was to the molecular level, where the corrosive intensity of each of the local aggressive factors in the stomach was superposed into the total corrosive intensity.[
28] As a result, the roles of gastric acid,
H. pylori, and NSAIDs in peptic ulcers were fully elucidated, as well as all the clinical observations/phenomena associated with the disease. The third application in this fourth article is the most representative at the societal level, where the individual mortality rates were superposed to reproduce the fluctuation curves. Significantly,
superposition mechanism is also the key methodological concept for a full understanding of another epidemiological observation in the fifth article of the series, seasonal variation, which has remained an unresolved mystery for more than 90 years in modern medicine. It is worth mentioning that the pre-applications of the
superposition mechanism have painted two complete pictures of the pathogenesis of cancer and AIDS. All these stories suggests that
superposition mechanism is universally applicable to elucidating any life phenomenon and human disease.