Background factors involved in the epidemiology of functional constipation in the Japanese population: a cross-sectional study

Yamamoto, Sayuri; Ohashi, Wataru; Yamaguchi, Yoshiharu; Inamoto, Shunsuke; Koshino, Akira; Sugiyama, Tomoya; Nagao, Kazuhiro; Tamura, Yasuhiro; Izawa, Shinya; Ebi, Masahide; Usami, Jun; Hamano, Koichi; Izumi, Junko; Wakita, Yoshinori; Funaki, Yasushi; Ogasawara, Naotaka; Sasaki, Makoto; Maekawa, Masato; Kasugai, Kunio

doi:10.1186/s13030-022-00237-2

Research
Open access
Published: 10 March 2022

Background factors involved in the epidemiology of functional constipation in the Japanese population: a cross-sectional study

Sayuri Yamamoto ORCID: orcid.org/0000-0002-2729-5078^1,2,
Wataru Ohashi³,
Yoshiharu Yamaguchi¹,
Shunsuke Inamoto²,
Akira Koshino¹,
Tomoya Sugiyama¹,
Kazuhiro Nagao¹,
Yasuhiro Tamura¹,
Shinya Izawa¹,
Masahide Ebi¹,
Jun Usami²,
Koichi Hamano²,
Junko Izumi²,
Yoshinori Wakita²,
Yasushi Funaki¹,
Naotaka Ogasawara¹,
Makoto Sasaki¹,
Masato Maekawa² &
…
Kunio Kasugai¹

BioPsychoSocial Medicine volume 16, Article number: 8 (2022) Cite this article

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Abstract

Background

Functional constipation (FC), a functional bowel disorder with symptoms of constipation, has considerable impact on quality of life. As data regarding its prevalence and epidemiology are lacking, this study aimed to evaluate the prevalence, population composition, lifestyle, quality of life, and clinical characteristics of these individuals by comparing people with and without FC. These parameters were also compared among individuals with strong and weak awareness of constipation.

Methods

An internet survey was conducted among 10,000 individuals aged 20–69 years from the general Japanese population; they were registered with an internet survey company. The following data were obtained: age, sex, educational history, occupation, residence, history of other diseases, lifestyle (including smoking/drinking habits using the Japanese Health Practice Index, medication use, symptoms of constipation according to the Rome III criteria, stool types according to the Bristol stool scale, and use of laxatives, including the place of purchase and cost per month or acceptable cost per month. The 8-item Short Form Health Survey Questionnaire was also used; FC was diagnosed based on Rome III criteria. All respondents were classified according to their awareness of constipation (i.e. strong or weak), and their characteristic features were compared.

Results

The data of 3000 respondents were evaluated; 262 (8.7%) had FC, which was common among older adults, women, and homemakers. FC was associated with changes in the frequency of bowel movement, sensation of incomplete or scanty evacuation, and the use of manual maneuvers; these are consequential clinical symptoms of FC. These individuals frequently skipped breakfast, had insufficient sleep, had more severe constipation, and had purchased laxatives in pharmacies or online more often than those without FC. A strong awareness of constipation was significantly more prevalent among women and homemakers. A history of anemia and cardiovascular disease was significantly more frequent in the strong awareness group, whereas a history of hypertension was more frequent in the weak awareness group.

Conclusions

Appropriate and comprehensive management should be provided for FC, based on the understanding of its characteristic features and considering the symptoms and lifestyle.

Background

The definition and diagnostic criteria for chronic constipation have been recently updated in the Rome IV criteria [1]. According to this classification, functional constipation (FC) is diagnosed when two or more of the following six symptoms are present: “straining during at least 25% of defecations”, “lumpy or hard stools (type 6 or 7 on the Bristol stool scale)” [2, 3], “sensation of incomplete evacuation,” “sensation of anorectal obstruction,” “manual maneuvers to facilitate defecation,” and “fewer than three defecations per week”. It is also diagnosed when both the following conditions are met: “loose stools rarely present without use of laxatives” and “does not meet Rome IV criteria for irritable bowel syndrome (IBS)”. For defining chronic constipation, these conditions must be met for the past 3 months, with symptom onset at least 6 months prior to diagnosis [4]. The Japanese Clinical Guidelines for Chronic Constipation 2017 defined constipation as a “state in which feces that should be eliminated from the body cannot be passed in sufficient quantity and in comfort”. The guidelines explained that it can “cause symptoms requiring examination and treatment due to reduced frequency of defecation (e.g. abdominal pain and abdominal bloating, among others), hard stools (e.g. difficulty in defecating and excessive straining during defecation, among others), or evacuation disorder (e.g. difficulty in defecating even loose stools, excessive straining during defecation, sensation of incomplete evacuation and therefore frequent defecation).” Reports suggest that chronic constipation affects 1–27% of the population, with the wide range attributed to variations in the population studied, definition used, and evaluation methods [4]. Chronic constipation is a highly prevalent disorder, characterized by gastrointestinal symptoms. It is frequently encountered in different medical specialties, and not only in gastroenterology [5]. A study on the impact of various functional gastrointestinal disorders, including constipation, on survival reported that chronic constipation conferred a significantly higher risk of poorer survival than other disorders, and it should therefore be given due consideration [6]. Prior to the establishment of guidelines, initial diagnoses and treatment approaches were based on the individual experience of the physician. Thus, there is limited information on the prevalence and actual disease status of patients with constipation. Moreover, few patients seek consultation for constipation as their chief complaint. Those with the condition either tend to self-medicate using over-the-counter (OTC) medications, or modify their lifestyle themselves [5, 7,8,9]. This is due to the fact that constipation is not regarded as a disease [10], there is no clear definition or diagnostic criteria for chronic constipation, and initial diagnosis and treatment approaches are based on clinical experience. Although evidence-based management of constipation has recently been promoted since the publication of the Clinical Guidelines for Chronic Constipation 2017 [4], there are only a few reports of its large-scale implementation [8, 11, 12]. In Japan, there are only two existing reports [8, 13] on the public awareness of constipation, its actual incidence, and on medication use and quality of life (QOL) of these patients. Therefore, much remains unknown regarding the epidemiology of FC and its background, including the status of constipation, medication, and treatment satisfaction. In this study, we performed an online survey to determine the actual prevalence of FC in Japan to investigate the frequency of symptoms, background factors, treatment, and QOL.

In Japanese subjects with awareness of constipation, the frequency and FC-related factors as per the Rome III criteria [14] were compared to those of individuals without FC (non-FC). Factors associated with a strong awareness of constipation were also studied.

Methods

Subjects

The survey was conducted between October 8 and 11, 2016, among 10,000 individuals aged 20–69 years from the Japanese general population. They were registered with Rakuten Insight (Osaka, Japan), an internet survey company. All survey participants provided informed consent. Valid answers were received from 9523 subjects, 4908 (51.5%) who indicated “I strongly think I have constipation” or “I think I have constipation” in response to the question, “Do you think you have constipation?” In this context, the awareness of constipation is a subjective sensation that can depend on the individual’s strength of awareness. The perceived strength of the condition may be affected by differing lifestyles and background circumstances. In this study, we used a highly subjective index of the strength of constipation awareness to evaluate real-world ordinary consumers based on patient reported outcomes. This was achieved using only the above question. Among the 4908 subjects with awareness of constipation, 3000 were randomly extracted by fitting the general population composition ratio based on prefecture, sex, and age. This was considered to reflect the demographic profile in Japan, as estimated by the Statistics Bureau, Ministry of Internal Affairs and Communications of Japan as of October 1, 2014.

Exclusion criteria

Those with organic diseases such as cancer and inflammatory diseases, neurological or endocrine disorders, and secondary constipation induced by medication (e.g. opioids, antidepressants, anticholinergic agents, calcium blockers, and proton pump inhibitors, among others) were excluded from the survey.

Survey

The information obtained from each study participant included the following: age, sex, educational history, occupation, residence, history of other diseases, lifestyle (including smoking/drinking habits using the Japanese Health Practice Index [JHPI]), medication use, symptoms of constipation according to the Rome III criteria [14], stool types according to the Bristol stool scale [2, 3], and use of laxatives (including the place of purchase and cost per month or acceptable cost per month). Participants also responded to an 8-item Short Form Health Survey Questionnaire (SF-8) [15]. FC was diagnosed based on the Rome III criteria [14], which differs from the Rome IV criteria in terms of the diagnosis of IBS. As per the former, the diagnosis of IBS entails chronic abdominal pain or discomfort experienced for at least 3 days per month instead of at least 1 day per week.

Among the 3000 participants whose data were analyzed, those who responded “I think so” to the question “Do you usually think that you have constipation?” were classified into the strong awareness group, and the rest were classified into the weak awareness group. A comparative study was conducted among the groups.

Statistical analysis

The level of significance for the statistical analysis was set at P < 0.05 (two-sided), and the two-sided 95% confidence interval was calculated where appropriate. To calculate the confidence interval of a proportion and the 95% confidence interval of a proportion of cases, the exact method (Clopper-Pearson) based on the F-distribution was used. Unpaired t-tests were used to compare continuous data between the two groups. We used the Fisher’s exact test to compare categorical (nominal) variables and investigate whether the proportions of one variable differed from the values of another. In addition, we used pairwise comparisons between proportions, with Benjamini-Hochberg adjustment of the P values, to further identify the categories of nominal variables showing significant differences. Logistic regression, with awareness of constipation as a dependent variable, was used to analyze factors related to awareness of constipation. For multivariate analysis, all variables were entered using forced entry. The Cochran-Armitage trend test was used to evaluate stool form by cost per month or acceptable cost per month.

Ethical approval

This study was approved by the Institutional Review Board of the Aichi Medical University (approval number: 2016-M025; approved on October 6, 2016). It was performed in compliance with the principles of the Declaration of Helsinki, and the Ethical Guidelines for Medical and Health Research Involving Human Subjects, enacted by the Japanese Ministry of Education, Culture, Sports, Science and Technology and the Ministry of Health, Labour and Welfare (December 22, 2014). The internet survey and statistical analysis of the data were outsourced to Rakuten Insight, Inc. (Osaka, Japan). Participants were free to withdraw their consent at any time via the Internet.

Results

Comparison of functional and non-functional constipation in the Japanese population

Background factors

Among the 3000 subjects included, 262 (8.7%) and 2738 (91.3%) were classified into the FC and non-FC groups, respectively (Table 1). The percentage of women was significantly higher in the FC than in the non-FC group (72.1 and 47.8%, respectively; P < 0.001). Similarly, the mean age was significantly higher in the FC group (49.8 ± 13.1 vs. 45.8 ± 13.3 years; P < 0.001). The demographic trend showed a higher occurrence of FC in older adults, with a significantly higher frequency in those aged 60 and older (Fig. 1A). The non-FC group had a significantly higher body mass index (BMI) than the FC group (21.7 ± 3.6 vs. 21.0 ± 3.3 kg/m², respectively; P = 0.002); however, the BMI in both groups was lower than the national average.

Table 1 Univariate analysis of participant characteristics in the functional constipation (FC) and non-FC groups, presented as the frequency or mean ± standard deviation (SD)

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A higher proportion of subjects in the non-FC group indicated that they were either office workers (46.2% vs. 39.3%, respectively; P = 0.030) or retired/unemployed (16.0% vs. 11.1%; P = 0.030). Conversely, there were significantly more homemakers in the FC group than in the non-FC group (27.5% vs. 14.4%, respectively; P < 0.001). Finally, the non-FC group had a higher proportion of individuals with a history of type 2 diabetes mellitus (7.2% vs. 1.1%; P < 0.001), hypertension (13.8% vs. 9.5%; P = 0.060), anemia (17.1% vs. 13.7%; P = 0.190), and hyperlipidemia (11.4% vs. 9.5%; P = 0.410), as well as a past treatment history of hypertension (10.1% vs. 5.3%; P = 0.010) and cardiovascular disease (3.0% vs. 0.4%; P = 0.010). However, significant differences were only noted in the history of type 2 diabetes mellitus and in the past treatment history of hypertension and cardiovascular disease.

Lifestyle

The JHPI lifestyle survey revealed that the occurrence of previous weight gain ≥10 kg was significantly more frequent in the non-FC group than in the FC group (23.0% vs. 17.2%; P = 0.036). No association was found between FC and drinking, smoking, eating, walking, or exercising. A strong awareness of constipation was a significant factor for not having FC (Table 1).

Quality of life

Evaluation of the QOL of participants using the SF-8 questionnaire [15] revealed that subjects in the FC group had a significantly higher mental component summary (MCS) than those in the non-FC group (46.7 ± 8.3 vs. 44.4 ± 9.2, respectively; P < 0.001); this included vitality (VT, feeling exhausted), social functioning (SF, having problems with family or friends), role emotional (RE, having difficulty in work or daily activity for psychological reasons), and mental health (MH, being nervous or depressed) (Table 1).

Clinical symptoms

A comparison of the two groups based on the Rome III criteria revealed that the following conditions occurred significantly more frequently in subjects in the FC group than in the non-FC group: straining, hard stool, sensation of incomplete evacuation, sensation of anorectal obstruction, rare bowel movements without the use of laxatives, and manual maneuvers to facilitate support of the pelvic floor at least 25% of defecation (Table 1). Loose stools that are rarely present without the use of laxatives is a Rome III criterion for FC. All FC subjects (100%) affirmed this symptom compared with only 30.8% of non-FC subjects (P < 0.001). Although there was no significant difference between the groups in terms of the use of manual maneuvers (6.9% vs. 5.3% in the FC and non-FC groups, respectively; P = 0.254), very few used manual maneuvers to facilitate defecation. A significantly lower percentage of subjects with FC had stools corresponding to Bristol stool scale type 4 (i.e. normal stool) compared with those without FC (12.2% vs. 26%, respectively; P < 0.001) (Fig. 2).

Source of laxative and acceptable cost

A significantly higher proportion of FC subjects used laxatives compared with non-FC subjects (53.4% vs. 28.7%; P < 0.001). While no significant difference was found between the groups based on laxative purchase by physician’s prescription, laxative purchase in pharmacies, and laxative purchase online, these were more common in the FC group (Fig. 3). There was significantly more variation among FC subjects in terms of the amount they were willing to pay for laxatives (P < 0.001), and they paid a significantly higher amount than non-FC subjects (P < 0.001) (Fig. 4).

Significant background factors

Factors found to be significant on univariate analysis in the FC group were included in the multivariate logistic regression analysis, using a detection rate of ≤0.2%. Age, sex, and certain clinical symptoms based on the Rome III criteria, including sensation of incomplete evacuation for at least 25% of defecation, sensation of hard evacuation, and manual maneuvers for facilitating support of the pelvic floor for at least 25% of defecation, were found to be significant background factors related to FC. Factors found to be significant for non-FC were onset associated with a change in frequency of stool, and Bristol stool type 4. (Table 2).

Table 2 Multivariate analysis of significant background factors for functional constipation (FC)

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