Comparison of functional and non-functional constipation in the Japanese population
Background factors
Of the 3,000 subjects extracted, 262 subjects (8.7%) were classified into the FC group and 2,738 subjects (91.3%) were classified into the non-FC group (Table 1). The percentage of women was significantly higher in the FC group 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 populations, with a significantly higher frequency in individuals aged 60 and older than in other age groups (Figure 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 = 0.02); however, the BMI in both groups was lower than the national average.
A higher proportion of subjects in the non-FC group than in the FC group answered 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), whereas 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 higher proportions 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 past treatment history of hypertension with hypertensive drugs (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 with hypertensive drugs and cardiovascular disease.
Lifestyle
The JHPI lifestyle survey revealed that the occurrence of a past 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
The evaluation of the QOL of participants using the SF-8 questionnaire15 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), which 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, and 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 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 stool corresponding to Bristol stool scale type 4 (i.e. normal stool) compared with those without FC (12.2% vs. 26%, respectively; P < 0.001) (Figure 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 on the laxative purchase by a physician’s prescription, laxative purchase in pharmacies, and laxative purchase online, these were more common in the FC group (Figure 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) (Figure 4).
Significant background factors
Factors found to be significant for the FC group in the univariate analysis were subjected to multivariate logistic regression analysis using a detection rate of ≤ 0.2%. Age, sex, and some clinical symptoms based on Rome III criteria, including sensation of incomplete evacuation for at least 25% of defecation, sensation of hard evacuation, and manual maneuvers to facilitate support of the pelvic floor at least 25% of defecation, were found to be significant background factors related to FC. Factors found to be significant for the non-FC were onset associated with a change in frequency of stool and Bristol stool type 4. (Table 2).
Comparison between strong and weak awareness of constipation
Background factors
The survey participants (n = 3,000) were also classified into either strong awareness or weak awareness of constipation. A strong awareness was significantly more prevalent in women than in men (57.3% vs. 42.7%; P < 0.001) (Table 3). A stronger awareness of constipation was observed among men in their 40s (Figure 1B). The average BMI was significantly higher in the weak awareness group; however, the subjects in both groups had a mean BMI lower than the national average in Japan.
A higher proportion of subjects in the weak awareness group answered that they were retired or unemployed than in the strong awareness group (17.0% vs. 14.0%; P = 0.030), whereas there were significantly more homemakers in the strong awareness group (17.5% vs. 13.9%; P = 0.006). Additionally, the strong awareness group had a significantly higher level of education, with a bachelor’s degree or over (52.3% vs. 39.7%; P = 0.020).
A past medical history of anemia (19.3% vs. 14.7%; P < 0.001) and cardiovascular disease (3.5% vs. 2.1%; P = 0.030) were significantly more frequent in the strong awareness group than in the weak awareness group, whereas a history of hypertension (14.7% vs. 11.8%; P = 0.020) was more frequent in subjects with weak awareness of constipation (Table 3).
Lifestyle
The evaluation of lifestyle using the JHPI survey showed that subjects with weak awareness of constipation “exercise aerobically for ≥30 minutes twice a week for at least 1 year” and “walk faster than other people of the same age” more frequently than subjects with strong awareness of constipation. Subjects with strong awareness of constipation have “dinner within 2 h before going to sleep ≥ 3 times a week”, a “snack after dinner ≥ 3 times a week”, “skip breakfast ≥ 3 times a week,” and do not “get enough sleep” significantly more frequently, implying that subjects with an unhealthy lifestyle had a strong awareness of constipation.
Quality of life
The evaluation of the QOL of participants using the SF-8 questionnaire revealed that subjects with a weak awareness of constipation had a significantly higher MCS (45.1 ± 8.7, vs. 44.0 ± 9.7; P < 0.001) and physical component summary (PCS) than those with a strong awareness of constipation (Table 3).
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 with strong awareness of constipation: straining, hard stool, sensation of incomplete evacuation, anorectal obstruction, manual maneuvering to facilitate evacuation, and rare bowel movements without the use of laxatives (Table 3).
Subjects with a strong awareness of constipation had a significantly higher percentage of stools corresponding to Bristol stool scale types 6 and 7, whereas those with a weak awareness had types 4 (normal stool) and 5 (Figure 2).
Significant background factors
Significant factors for strong awareness in the univariate analysis were subjected to multivariate logistic regression analysis using a detection rate of ≤ 0.2%. The female sex, sensation of incomplete evacuation for at least 25% of defecations, sensation of hard evacuation, and loose stools rarely present without the use of laxatives were found to be significant background factors related to a strong awareness of constipation. On the other hand onset associated with a change in frequency of stool, Bristol stool type 4 were associated with weak awareness of constipation. (Table 4).