Prevalence of multimorbidity in a geographically defined American population: patterns by age, sex, and race/ethnicity

Abstract

Objective: To describe the prevalence of multimorbidity involving 20 selected chronic conditions in a geographically defined US population, emphasizing age, sex, and racial/ethnic differences.

Patients and methods: Using the Rochester Epidemiology Project records linkage system, we identified all residents of Olmsted County, Minnesota, on April 1, 2010, and electronically extracted the International Classification of Diseases, Ninth Revision codes associated with all health care visits made between April 1, 2005, and March 31, 2010 (5-year capture frame). Using these codes, we defined the 20 common chronic conditions recommended by the US Department of Health and Human Services. We counted only persons who received at least 2 codes for a given condition separated by more than 30 days, and we calculated the age-, sex-, and race/ethnicity-specific prevalence of multimorbidity.

Results: Of the 138,858 study participants, 52.4% were women (n=72,732) and 38.9% had 1 or more conditions (n=54,012), 22.6% had 2 or more conditions (n=31,444), and 4.9% had 5 or more conditions (n=6853). The prevalence of multimorbidity (≥2 conditions) increased steeply with older age and reached 77.3% at 65 years and older. However, the absolute number of people affected by multimorbidity was higher in those younger than 65 years. Although the prevalence of multimorbidity was similar in men and women overall, the most common dyads and triads of conditions varied by sex. Compared with white persons, the prevalence of multimorbidity was slightly higher in black persons and slightly lower in Asian persons.

Conclusion: Multimorbidity is common in the general population; it increases steeply with older age, has different patterns in men and women, and varies by race/ethnicity.

Figure 1

Age- and sex-specific prevalence (per 1,000 population) of the 20 chronic conditions considered separately. We used the same age groups as used in Tables 1 and 2 and in Supplemental Table 2; prevalence figures were plotted at the mid-point of each interval (e.g., at 10 years for 0-19 years). We used different scales for the y-axis to better show the age and sex patterns. Therefore, the magnitude of the differences cannot be compared across conditions (e.g., asthma vs. HIV). The 20 panels are presented by rows in decreasing order of frequency (by overall age- and sex-standardized prevalence).

Figure 2

Prevalence (per 100 population) of combinations of 1 or more, 2 or more (multimorbidity), or 5 or more of the 20 chronic conditions in men and women separately (panels A, C, and E), and stratified by ethnicity (panels B, D, and F). We used different scales for the y-axis in panels E and F to better show the differences.

Figure 3

Panel A, heat map of the burden of multimorbidity in terms of absolute frequency. The number in each square is the percent of co-occurrence in the overall population (all ages combined). The 18 conditions are listed on the X and Y axes of both panels in order of frequency. Panel B, heat map of the risk ratios obtained by dividing the observed frequency of each pair of 18 conditions by the frequency expected assuming independent probabilities. The ratios provide a cross-sectional measure of association. Autism spectrum disorder and human immunodeficiency virus infection were excluded in both panels because they were uncommon in the overall population. The color scale used for each panel is shown on the right. Values for men are shown in the lower right triangle, and values for women are shown in the upper left triangle. Definition of acronyms or abbreviations in order of frequency: LIP = hyperlipidemia; HTN = hypertension; DEP = depression; DIA = diabetes; ART = arthritis; CAN = cancer; ARR = cardiac arrhythmias; AST = asthma; CAD = coronary artery disease; SUB = substance abuse disorders; COPD = chronic obstructive pulmonary disease; OST = osteoporosis; CKD = chronic kidney disease; STR = stroke; CHF = congestive heart failure; DEM = dementia; SZO = schizophrenia; HEP = hepatitis.