Multiple Sclerosis Journal - October 2017 - 1510

Multiple Sclerosis Journal 23(11)
Table 2. Adjusted odds ratios (aOR) and rate ratios (aRR) for infection-related hospitalizations in people with multiple sclerosis as compared
with controls.

All infection-related hospital
admissions
MS population versus controls
MS population versus controls
stratified by sex
Males
Females
MS population versus controls
stratified by age (years)
18-39
40-49
50-59
60+

Five most common infectionrelated hospital admissions
Infections of the urinary system
Pneumonia
Intestinal infections
Infections of the skin and
subcutaneous tissue
Sepsis

Number (%) of people with ⩾1
hospitalization

Model 1

Model 2

Model 3

MS population

Controls

OR (95%)

aOR (95%)

aOR (95%)

780 (10.9)

1804 (5.0)

2.41 (2.18-2.66)

2.44 (2.21-2.70)

2.39 (2.16-2.65)

229 (12.2)
551 (10.4)

486 (5.2)
1318 (5.0)

2.77 (2.30-3.34)
2.27 (2.02-2.55)

3.03 (2.50-3.67)
2.26 (2.01-2.54)

3.03 (2.50-3.68)
2.19 (1.95-2.46)

1.51 (1.18-1.94)
2.54 (2.05-3.15)
2.70 (2.25-3.24)
2.76 (2.38-3.21)

1.48 (1.16-1.90)
2.50 (2.01-3.10)
2.69 (2.24-3.23)
2.70 (2.32-3.14)

1.46 (1.14-1.87)
2.36 (1.90-2.94)
2.59 (2.15-3.11)
2.71 (2.33-3.15)

Number of hospitalizations per 10,000
person-years

Model 1

Model 2

Model 3

MS population

Controls

RR (95%)

aRR (95%)

aRR (95%)

76
33
22
16

23
13
9
7

3.24 (3.08-3.41)
2.47 (2.33-2.61)
2.52 (1.98-3.20)
2.25 (2.11-2.39)

3.32 (3.16-3.49)
2.63 (2.48-2.78)
2.60 (2.05-3.29)
2.26 (2.12-2.41)

3.26 (3.10-3.43)
2.58 (2.44-2.73)
2.55 (2.01-3.23)
2.19 (2.06-2.33)

14

7

2.12 (1.56-2.87)

2.21 (1.64-2.97)

2.21 (1.64-2.97)

179 (6.9)
223 (9.9)
189 (13.3)
189 (20.4)

487 (3.8)
458 (4.1)
365 (5.1)
494 (10.8)

MS: multiple sclerosis; OR: odds ratio; RR: rate ratio; SES: socioeconomic status.
Model 1: crude (people with MS and controls matched by sex, year of birth, and place of residence; no additional adjustments made); Model 2: as for Model 1,
plus adjustment for sex (except for the sex-specific models), age (continuous, except for the age-specific models), year of index date (1996-2001, 2002-2007,
and 2008-2013), SES (quintiles), immunotherapy use not specific to MS (yes, no); Model 3: as for model 2, plus adjustment for the number of comorbidities
(none, 1, and ⩾2).

Prescriptions filled for antimicrobials
People with MS filled 57% (aRR: 1.57; 95% CI:
1.49-1.65) more prescriptions for antimicrobials than
the matched controls (Table 4; model 3). There were
differences in the number of antimicrobial prescriptions between people with and without MS among
men (aRR: 1.72; 95% CI: 1.54-1.92) and among
women (aRR: 1.54; 95% CI: 1.45-1.62), and within
each age group, rising from 32% more prescriptions
in those under 40 years of age to 66% in those aged
⩾60 years. Compared with the matched controls, people with MS filled between 51% and 61% more prescriptions for antibiotics, antivirals, and antimycotics
(Table 4; model 3). Low prescription frequencies prevented separate analyses for antiprotozoals (<5/10,000

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PY), antihelminthics (8/10,000 PY), and antimycobacterials (25/10,000 PY).
Complementary analyses
Neither complementary analyses changed interpretation of findings (Appendix e-2). Censoring at initiation of a MS-specific immunomodulatory drug
decreased the median follow-up time by 2.6 years and
resulted in a somewhat lower magnitude of effect for
hospitalizations, but the aOR remained above 2. Little
change was observed for physician visits and prescriptions filled (Supplementary Appendix e-2; Table
e-3a) compared to the main analyses. When infectionrelated encounters within a 2-week period were

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