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. Author manuscript; available in PMC: 2023 May 1.
Published in final edited form as: Clin Gastroenterol Hepatol. 2021 Jun 30;20(5):1085–1094. doi: 10.1016/j.cgh.2021.06.027

The Epidemiology of Microscopic Colitis in Olmsted County, Minnesota: Population-Based Study from 2011–2019

June Tome 1, Kanika Sehgal 1, Amrit K Kamboj 2, William S Harmsen 3, Patricia P Kammer 2, Edward V Loftus 2, William J Tremaine 2, Sahil Khanna 2, Darrell S Pardi 2
PMCID: PMC8716639  NIHMSID: NIHMS1720232  PMID: 34216819

Abstract

BACKGROUND:

Epidemiological studies from Europe and North America report an increasing incidence of microscopic colitis (MC) in the late twentieth century followed by a plateau. This population-based study assessed recent incidence trends and the overall prevalence of MC over the past decade.

METHODS:

Residents of Olmsted County, Minnesota diagnosed with collagenous colitis (CC) or lymphocytic colitis (LC) between January 1, 2011 and December 31, 2019 were identified using the Rochester Epidemiology Project. Clinical variables were abstracted by chart review. Incidence rates were age- and sex-adjusted to the 2010 US population. Associations between incidence and age, sex, and calendar periods were evaluated using Poisson regression analyses.

RESULTS:

A total of 268 incident cases of MC were identified with a median age at diagnosis of 64 years (range, 19–90); 207 (77%) were women. The age- and sex-adjusted incidence of MC was 25.8 (95% confidence interval [CI] 22.7–28.9) cases per 100,000 person-years. The incidence of LC was 15.8 (95% CI, 13.4–18.2) and CC 9.9 (95% CI, 8.1–11.9) per 100,000 person-years. A higher MC incidence was associated with increasing age and female sex (p<0.01). There was no significant trend in age- and sex-adjusted incidence rate over the study period (p=0.92). On December 31, 2019, the prevalence of MC, LC, and CC (including cases diagnosed before 2011) was 246.2, 146.1, and 100.1 per 100,000 persons, respectively.

CONCLUSION:

The incidence of MC and its subtypes was stable between 2011–2019, but its prevalence is higher than in previous periods. MC incidence continues to be associated with increasing age and female sex.

Keywords: microscopic colitis, epidemiology, collagenous colitis, lymphocytic colitis, incidence, prevalence

Graphical Abstract

graphic file with name nihms-1720232-f0008.jpg

Introduction:

Microscopic colitis (MC) is an inflammatory disease of the colon that is a relatively common cause of watery diarrhea, especially in older patients. The two subtypes of MC, lymphocytic colitis (LC) and collagenous colitis (CC), can be distinguished based on their histological findings, with CC characterized by a thickened subepithelial collagen band in addition to the intraepithelial lymphocytosis with a dense inflammatory infiltrate in the lamina propria that is seen in LC.1 Risk factors for the development of MC include increasing age, with the average age at diagnosis generally over 50 years, and female sex. Other autoimmune diseases such as rheumatoid arthritis, hypothyroidism and hyperthyroidism, and celiac disease are often seen in these patients.2 Certain medications have also been associated with MC including nonsteroidal anti-inflammatory drugs (NSAIDs), proton pump inhibitors (PPIs), statins, and selective serotonin reuptake inhibitors (SSRIs).3–6

Epidemiological studies from Europe and North America reported increasing incidence trends of MC and its subtypes in the late twentieth century,7–9 while more recent data show a general plateau in MC incidence rates.10–14 A recent systematic review and meta-analysis reported a pooled incidence of 4.14 per 100,000 persons for CC and 4.85 per 100,000 persons for LC.7 The incidence of MC in Olmsted County, Minnesota (MN), increased from 1985–2001 and stabilized between 2002–2010.8,12 We performed a population-based study to assess the recent incidence trends and the overall prevalence of MC and its subtypes over the past decade in our region.

Methods:

Study Setting

Olmsted County is located in southeastern, MN with Mayo Clinic and Olmsted County Medical Center as the two main health systems. At the time of the April 2010 census, the population in the county was 144,248 with the most recent population census estimate in July 2019 of 158,293.15–16 It is the seventh most populated county in MN. Regarding ethnic diversity, the largest racial groups are Caucasian (80.6%), followed by Asian (5.8%) and African American (5.8%). The median age for residents in 2019 was 37.2 years and 15.9% of residents were 65 years or older. In 2018, the median household income of Olmsted County residents was $74,880 and 44% of residents had obtained a bachelors degree or higher level of education.15–16 Other than a higher average income and a higher rate of college education, Olmsted County is similar to the US average.

Rochester Epidemiology Project

The Rochester Epidemiology Project (REP) is a medical records linkage system that provides longitudinal medical data for Olmsted County, MN residents across all community healthcare providers. The medical records include all outpatient clinic visits, hospitalizations, procedures, and emergency room visits across multiple healthcare organizations. The REP was created in 1966 and this unique medical records linkage system allows investigators to conduct population-based studies following the natural history of a disease in addition to incidence, prevalence, and specific clinical outcomes.17–20

Study Population

Residents of Olmsted County, MN, age 18 years or older, diagnosed with CC or LC from January 1, 2011 through December 31, 2019 were identified based on pathology reports using the REP and confirmed by chart review. Patients with a diagnosis of non-specific colitis and those who did not meet diagnostic histology criteria for LC or CC were excluded. Additionally, 7 patients diagnosed with inflammatory bowel disease either before or after their MC diagnosis were excluded. Patient demographics including sex, race, and age at MC diagnosis were collected. Abstracted clinical variables included MC histologic subtype (LC or CC), body mass index (BMI), smoking status (never, former, current), presence of other autoimmune diseases, medications associated with MC used within 3 months of diagnosis including statins, SSRIs, PPIs, aspirin, other NSAIDs, and histamine H2-receptor antagonists. Presence of active disease in prevalent cases, defined as the presence of diarrhea due to MC and/or on medications (loperamide, budesonide, bismuth subsalicylate, cholestyramine, mesalamine, and biologic agents) for treatment of MC within 6 months of the prevalence date, was collected by chart review. Duration of follow-up was calculated from date of MC diagnosis to date of last clinic follow-up visit.

Statistical Analysis

For patient and clinical characteristics, continuous variables were reported as means with standard deviation (SD) and categorical variables as median (range) or frequency with percentages. Incidence rates were age- and sex-adjusted to the 2010 US population, with interpolation between census years. Associations between incidence and age, sex, and 3-year interval calendar periods starting in 2011 were evaluated using Poisson regression analyses. Age and calendar periods were evaluated as continuous predictors. Standard errors and 95% confidence intervals (CIs) were calculated for the incidence and prevalence rates assuming a Poisson distribution.

MC incidence rate was calculated assuming the entire county population over the age of 18 years was at risk. Prevalence was calculated using patients with a diagnosis of MC living in Olmsted County, MN on December 31, 2019 as the numerator, with the estimated county population on that date as the denominator. A second prevalence analysis was performed using only patients with active disease within 6 months of prevalence date as the numerator. Patients who were diagnosed with MC prior to 2011–2019 or prior to becoming county residents, but who were residing in Olmsted County on December 31, 2019, were included in the prevalence calculations. Diagnosis rate was defined as the number of patients diagnosed with MC across a specific age group, divided by the number of colonoscopies with biopsies performed across the respective age group. The Poisson regression analyses were conducted using SAS software version 9.4 (SAS Institute Inc, Cary, NC) and R version 3.6.2. This epidemiological study was approved by the Mayo Clinic and Olmsted Medical Center institutional review boards.

Results:

A total of 268 incident cases of MC were identified with median age at diagnosis of 64 years (range, 19–90) and 207 (77%) were women. A total of 165 cases (62%) had LC and 103 (38%) had CC. The median BMI was 27.8 (range, 18.9–48.0) for LC and 26.8 (18.2–48.8) for CC. A total of 76 (46.1%) patients with LC and 41 (39.8%) with CC were never smokers, 63 (38.2%) with LC and 37 (35.9%) with CC were former smokers, and 26 (15.8%) with LC and 25 (24.3%) with CC were current smokers at MC diagnosis. There was no significant difference in smoking history between LC and CC cases (p = 0.22). The most common comorbid autoimmune disease was thyroid disorders (45 [16.8%]) had hypothyroidism or hyperthyroidism), followed by rheumatoid arthritis (13 [4.9%]), type-one diabetes mellitus (4 [1.5%]), celiac disease (3 out of 188 of the incident cases tested for CD by serology and/or biopsy, [1.6%]), multiple sclerosis (1 [0.4%]), Sjogren’s syndrome (1 [0.4%]), and vasculitis (1 [0.4%]). Patients used the following medications within 3 months of their MC diagnosis: NSAIDS including aspirin 163 (60.8%), statins 97 (36.2%), SSRIs 89 (33.2%), PPIs 84 (31.3%), and histamine-2 receptor antagonists 34 (12.7%) (Table 1).

Table 1.

Baseline characteristics of microscopic colitis patients diagnosed from 2011–2019.

Median ± Range or n (%)
Characteristics All Patients (n=268) Lymphocytic colitis (n=165) Collagenous colitis (n=103) p value
Age 64 (19–90) 63 (25–90) 66 (19–89) 0.08
Sex, female 207 (77.2%) 122 (73.9%) 85 (82.5%) 0.10
Race, white 261 (97.4%) 160 (96.9%) 101 (98.0%) 0.59
Body Mass Index (kg/m2) 27.3 (18.2–48.8) 27.8 (18.9–48.0)  26.8 (18.2–48.8) 0.45
Celiac disease 3 (1.6%) 1 (0.9%) 2 (2.6%) 0.31
Smoking History 151 (56.3%) 89 (54.0%) 62 (60.2%) 0.22
Medications SSRIs 89 (33.2%) 56 (33.9%) 33 (32.0%) 0.87
PPIs 84 (31.3%) 57 (34.5%) 27 (26.2%) 0.19
NSAIDs 163 (60.8%) 106 (64.2%) 57 (55.3%) 0.77
H2 blockers 34 (12.7%) 23 (13.9%) 11 (10.7%) 0.51
Statins 97 (36.2%) 62 (37.6%) 35 (33.9%) 0.72
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*

Medications used within 3 months of microscopic colitis diagnosis Celiac disease prevalence calculated based on patients who had testing (serology and/or biopsy) performed

The age- and sex-adjusted incidence of MC overall was 25.8 (95% CI, 22.7–28.9) cases per 100,000 person-years from 2011–2019, compared to 21.0 (95% CI, 18.0–24.1) cases per 100,000 person-years from 2002–2010 and 8.6 (95% CI, 7.1–10.0) per 100,000 person-years from 1985–2001 that we have reported in prior studies. The overall incidence of LC was 15.8 (95% CI, 13.4–18.2) and CC 9.9 (95% CI, 8.1–11.9) per 100,000 person-years from 2011–2019. MC incidence over the 3-year interval calendar periods is shown in Figure 1. LC and CC incidence over the 3-year interval calendar periods is shown in Figure 2. The incidence of MC and its subtypes were associated with increasing age (p<0.01) and female sex (p<0.01) (Figure 3A-C). There was no significant trend over the three calendar periods (2011–2013, 2014–2016, 2017–2019) in the overall MC, LC, and CC incidence rates (p=0.92, 0.42, and 0.24, respectively). There was also no significant trend in MC incidence rates comparing 2002–2010 and 2011–2019 calendar periods (p = 0.56). The number of colonoscopies and those with biopsies performed per year in Olmsted County, MN residents between 2011–2019 remained stable (Figure 4A). The average number of colonoscopies with biopsies performed varied by age group and those 80 years of age or greater had the lowest number of endoscopies performed, yet the highest diagnosis rate for MC (Figure 4B).

Figure 1.

Figure 1.

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Age-adjusted and sex-specific incidence of MC in Olmsted County, MN, 2011–2019.

Figure 2.

Figure 2.

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Age- and sex-adjusted incidence of MC and subtypes, LC and CC, in Olmsted County, MN, 2011–2019.

Figure 3A.

Figure 3A.

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Age- and sex-specific incidence of MC in Olmsted County, MN residents, 20112019.

Figure 4B.

Figure 4B.

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Age- and sex-specific incidence of LC in Olmsted County, MN residents, 20112019.

On December 31, 2019, a total of 308 residents of Olmsted County were alive with a diagnosis of MC, including 183 with LC and 125 with CC. The overall prevalence of MC, LC, and CC (including cases diagnosed prior to 2011) was 246.2 (95% CI, 218.6–273.7), 146.1 (95% CI, 124.9–167.4), and 100.1 (95% CI, 82.5–117.6) per 100,000 persons, respectively. The overall MC prevalence in women was 358.4 (95% CI, 312.9–403.9) and in men 122.5 (95% CI, 93.5–151.5) per 100,000 persons. A total of 98 (31.8%) of the 308 residents had active disease within 6 months of the prevalence date (diarrhea due to MC and/or were on any medications for treatment of MC), including 46 with LC and 52 with CC. The median duration of follow-up was 1.7 years (range 0.2–19 years), with 9 patients lost to follow-up. The prevalence of MC, LC, and CC (only including patients with active disease) was 78.9 (95% CI, 63.3–94.7), 36.8 (95% CI, 26.1–47.5), and 42.2 (95% CI, 30.7–53.6) per 100,000 persons, respectively.

Discussion:

The age- and sex-adjusted incidence of MC in Olmsted County, MN was stable from 2011–2019. The overall incidence of MC in Olmsted County, MN, increased from 1985–2001, stabilized between 2002–2010, and continues to demonstrate a plateau between 2011–2019. This is similar to studies from Europe and North America reporting an increasing incidence of microscopic colitis (MC) in the late twentieth century, and more recent data showing a plateau in MC incidence rates.7–14 European and North American studies have reported varying MC incidence rates ranging between 1 and 25 per 100,000 person-years.7, 21–23 The variation in reported incidence may be attributed to the differences in diagnostic methodology, geography and study settings, with distinct population structures including average age and ethnic composition.

The proposed reasons for the increased incidence of MC in the late twentieth century include overall increased awareness of the disease, an aging population, increased frequency of diagnostic colonic biopsies in patients with chronic unexplained diarrhea, and potentially increased use of certain medications such as proton pump inhibitors amongst others.24 The current stabilization of MC incidence that is demonstrated in a majority of recent studies may be explained by the decreased detection bias given that MC is now a relatively well recognized cause of chronic watery diarrhea.

Similar to prior studies, we demonstrate that the incidence of MC continues to be associated with increasing age and female sex which are both well-established risk factors for the development of MC.25–27 Recent studies have evaluated the frequency of diagnostic colonic biopsies on incidence, but have not examined rates across different age groups.28 The apparent drop in the incidence of MC observed in the most elderly, those 80 years or older, may be in part due to the decreased number of colonoscopies performed in this age group. In a French multicenter, prospective study, diagnosis of MC was associated with age over 50 years (OR, 3.1; 95% CI, 1.6–5.9), autoimmune disease (OR, 5.5; 95% CI, 2.5–12.0), and new medications (OR, 3.7; 95% CI, 2.1–6.6).29 Prior population-based studies of MC in Olmsted County from 1985–2001 and 2002–2010 have also shown an association between incidence and increasing age as well as female sex.8,12

A significant portion of Olmsted County patients used medications associated with a risk of MC such as statins, SSRIs, PPIs, aspirin, other NSAIDs, and histamine H2-receptor antagonists within three months of their diagnosis.29–30 Nonetheless, a recent US multicenter cohort study found an inverse association with PPIs and histamine H2-receptor antagonists when compared to controls with chronic diarrhea; only NSAID use was associated with MC.31 It is plausible these medications do not cause MC, but instead aggravate diarrhea and bring the diagnosis to clinical attention.

Additionally, a significant portion of Olmsted County patients were current smokers (19%) at the time of their MC diagnosis, compared to an average of 14%, 15.1%, and 16.1% current smokers for all adult Olmsted County residents, MN residents, and across the US respectively.32 Smoking appears to play a role in the development of MC, with studies demonstrating an increased risk of persistent disease with a lower probability of achieving clinical remission in smokers.27,33

The overall prevalence of MC on December 31, 2019 in Olmsted County, MN (246.2 cases per 100,000 residents) was higher than we have reported in prior studies (219.0 cases per 100,000 residents in 2010 and 103.0 cases per 100,000 residents in 2001).8,12 Increased incidence and increased diagnostic ability do not appear to account for the increasing prevalence, as the increase in new MC cases has stabilized since 2002 and the number of colonoscopies performed in Olmsted County has not significantly changed between the prior and current study periods. The increased prevalence of MC may be due to increased life expectancy, with patients overall living longer with associated comorbid conditions, including autoimmune diseases or to an increase in the median age in the county. The median age of Olmsted County residents in 2010 was 36.3 years. The proportion of residents who were aged 65 years and older increased from 12.6% in 2010 to 15.9% in 2019. This is similar to the national data across the US.32 In the setting of an aging population, the prevalence of MC is likely to continue to increase in the future. Rising prevalence is an important consideration when managing patients with MC who will be living with their condition for increasingly longer periods and may experience more intermittent disease remissions and relapses over time. We demonstrate that a significant proportion of patients with a history of MC do not have active disease at a given point in time. A recent European prospective cohort study showed approximately half of MC patients have a relapsing disease course, particularly during the first year of diagnosis.34

There are a few limitations to this study including the predominantly white population in Olmsted County, MN. Additionally, despite county residents being socioeconomically similar to the US population, residents have a higher level of education and a higher percentage work in the healthcare industry compared to residents nationwide.15–16 These demographic and socioeconomic factors may limit the generalizability of the results, with factors such as a patient’s health literacy and the likelihood to visit a physician for gastrointestinal symptoms influencing the incidence rates of MC. In addition, prevalence based on disease activity may be underestimated as loperamide can be obtained without prescription and not all patients with mild symptoms may seek medical care. Lastly, associated health conditions and use of medications were not compared to a matched population without MC in Olmsted County.

Despite several limitations, there are important strengths and implications from this longitudinal population-based study for current clinical practice. Epidemiological studies of incidence and prevalence are useful for estimating disease burden in a community, including healthcare resource allocation, and mitigating risk factors associated with a disease. Quality of life can be significantly reduced in MC patients with symptoms of chronic diarrhea, abdominal pain, or urgency, and particularly fecal incontinence.35 An important approach to managing patients with chronic watery diarrhea is to have a high index of suspicion for MC in patients with chronic diarrhea, especially female patients over 50 years old, and possibly in patients who use commonly recognized associated medications such as NSAIDs, SSRIs, or PPIs. With the increasing prevalence of MC, additional studies of risk factors, pathophysiology, natural history, and long-term management will become increasingly important.36

Although risk factors affecting the incidence and prevalence of MC such as age and gender have been studied, the ethnic variation in the epidemiology of MC remains unknown. Recent studies reported a higher prevalence of MC in zip codes with predominantly white populations versus a lower prevalence in ZIP codes with primarily non-white residents. A study of over 11,000 patients using a large pathology database in the US demonstrated significant ethnic differences in occurrence of MC, with an increased risk in Jewish patients and a decreased risk in those of Indian, East Asian, and Hispanic descent. 37–38, although it is unclear if these differences are due to racial/ethnic or socioeconomic factors. While our study demonstrates continued associations of MC with increasing age and female sex, further work is needed to explore additional socioeconomic and environmental risk factors that may play a role in the epidemiology of MC. These potential additional risk factors may account for some of the differences in incidence and prevalence of MC between different geographical areas.

Conclusion:

The incidence rates of MC and its subtypes LC and CC remained stable between 2011–2019, but its prevalence is higher than in previous periods. MC incidence continues to be associated with increasing age and female sex. We demonstrate that a significant proportion of subjects with a history of MC do not have active disease at a given point in time, which has implications for assessing overall burden of disease and interpreting other studies reporting prevalence rates.

Figure 5C.

Figure 5C.

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Age- and sex-specific incidence of CC in Olmsted County, MN residents, 20112019.

Figure 6A.

Figure 6A.

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Total number of colonoscopies performed in Olmsted County, MN by year.

Figure 7B:

Figure 7B:

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Diagnosis rates of MC based on total number of colonoscopies with biopsies performed in Olmsted County, MN by age group, 2011–2019.

BACKGROUND:

Epidemiological studies from Europe and North America report an increasing incidence of microscopic colitis (MC) in the late twentieth century followed by a subsequent plateau. This population-based study aimed to assess recent incidence trends and the prevalence of MC in Olmsted County, MN over the past decade.

FINDINGS:

The incidence of MC and its subtypes was stable between 2011–2019, but its prevalence is higher than in previous periods. MC incidence continues to be associated with increasing age and female sex.

IMPLICATIONS FOR PATIENT CARE:

In the setting of an aging population, the prevalence of MC is likely to continue to increase in the future. Rising prevalence is an important consideration in managing MC because patients may live with their condition for increasingly longer periods.

Acknowledgments

Funding: This study was made possible using the resources of the Rochester Epidemiology Project, which is supported by the National Institute on Aging of the National Institutes of Health under Award Number R01AG034676. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

DSP has grant funding from Pfizer, Vedanta, Seres, Finch, Applied Molecular Transport, and Takeda and has consulted for Vedanta and Otsuka. EVL has research support from AbbVie, Amgen, Bristol-Myers Squibb, Celgene, Gilead, Genentech, Janssen, Receptos, Robarts Clinical Trials, Takeda, Theravance, UCB and has consulted for AbbVie, Allergan, Amgen, Boehringer Ingelheim, Bristol-Myers Squibb, CALIBR, Celgene, Eli Lilly, Gilead, Genentech, Iterative Scopes, Janssen, Ono Pharma, Takeda, UCB.

Footnotes

Confllicts of Interest: The other authors have no conflicts of interest to report.

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