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Colds and Influenza-Like Illnesses in University Students: Impact on Health, Academic and Work Performance, and Health Care Use

  1. Kristin L. Nichol1,2,
  2. Sarah D Heilly1,2, and
  3. Edward Ehlinger3
  1. 1Medicine Service, Veterans' Affairs Medical Center, Minneapolis
  2. 2Department of Medicine, Minneapolis
  3. 3Student Health Services, University of Minnesota, Minneapolis
  1. Reprints or correspondence: Dr. Kristin L. Nichol, Medicine Service (111), VA Medical Center, 1 Veterans' Dr., Minneapolis, MN 55417 (nichol014{at}umn.edu).
 
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Abstract

Background. Upper respiratory tract illnesses (URIs) are a major cause of morbidity among adults, with substantial direct and indirect costs to society, but their impact among university students has not been well described. We sought to assess the impact of URIs (colds and influenza-like illnesses [ILIs]) on the health, academic and work performance, and health care use of university students.

Methods. This was a cohort study of college students at the University of Minnesota, Twin Cities campus (Minneapolis-St. Paul), who were recruited during October 2002 and followed up from November 2002 through April 2003. All 42,000 registered students were invited via e-mail to participate. Baseline information was obtained in October 2002. Monthly follow-up information about colds or ILIs was obtained for the period of November 2002 through April 2003. Data were collected by use of Internet-based questionnaires.

Results. of 4919 volunteers, 3249 completed all follow-up surveys. The mean age was 22.7 years; 68% of the volunteers were female. Ninety-one percent had ⩾1 URI (83% had ⩾1 cold, and 36.7% had ⩾1 ILI). These URIs caused 6023 bed-days, 4263 missed school days, 3175 missed work days, and 45,219 days of illness. of the cohort, 22.2% had ⩾1 health care visit, and 15.8% used antibiotics to treat a URI; 27.8% did poorly on a test and 46.3% did poorly on a class assignment. ILIs versus colds had a much greater impact on all parameters (e.g., general health level was 55%–60% lower with ILI vs. no URI and 33%–39% lower for colds vs. no URI; P < .001 for each).

Conclusion. Colds and ILIs were common and associated with substantial morbidity in university students. Enhanced efforts to prevent and control URIs, especially influenza vaccination, could improve the health and well-being of the 17 million college and university students in this country.

Upper respiratory tract illnesses (URIs) cause substantial morbidity each year. The annual incidence is ∼2 to 4 episodes per adult [1, 2]. Among healthy adults <65 years of age, URIs account for hundreds of millions of days of illness and work loss, tens of millions of health care professional visits and antibiotic prescriptions, and billions of dollars in health care and lost productivity costs [3–5].

College and university students may be at increased risk for URIs, and outbreaks with high attack rates have been reported [6–9]. These studies, however, have generally focused on illness rates and symptoms, with relatively little attention to the impact of URIs on productivity and quality of life. We have initiated a serial cohort study to evaluate the incidence of URIs among university students and the impact on general health, health care use, and school and work performance. Here, we describe the experience of the first cohort.

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Methods

Patient enrollment and data collection. The Burden of Respiratory Illnesses among University and College Students Study is a serial cohort study providing ongoing assessments of URIs among students. Students enrolled at the Twin Cities campus of the University of Minnesota (Minneapolis–St. Paul) as of 1 October 2002 were invited by e-mail to participate in the initial cohort. The first notice was sent in mid October, with 2 follow-up e-mails sent 3 days apart from each other. Interested students were directed to an Internet site with detailed information about the study. Consenting students were assigned a unique pass code for use at a secure Internet site for completing a baseline and all follow-up surveys.

Volunteers completing the baseline survey before 1 November were enrolled and received e-mail reminders to complete monthly follow-up surveys from November 2002 through April 2003. E-mail reminders about the follow-up surveys were sent on the first weekday of the subsequent month, with an additional reminder 1 week later. Participants completing all surveys were eligible for a random drawing for a $500 gift certificate at a local book store (odds of winning, ∼1 in 1000). This study was approved by human studies committees at the Minneapolis Veterans' Affairs and the University of Minnesota.

The baseline questionnaire asked about demographic and social characteristics and health status. The follow-up surveys asked about occurrences of URIs, symptoms, impact on work and school life, health care use, and general health. URIs were defined as ⩾1 day of “upper respiratory infection/common cold symptoms.” Students with URIs who reported fever (or feeling feverish) and cough were classified as having an influenza-like illness (ILI). Students with URIs but not ILIs were classified as having a cold.

Statistical analysis. Descriptive statistical analysis of and bivariable comparisons between groups of students according to their respiratory tract illness status were conducted with SPSS for Windows, version 10.1 (SPSS).

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Results

A total of 4919 students completed the baseline survey, for a volunteer rate of ∼12% of the entire student body (∼42,000 students). of these, 4045 (82.2%) completed the November follow-up survey, whereas 3249 (66%) completed all of the surveys. The baseline characteristics of the participants completing all surveys were generally similar to the characteristics of all volunteers (table 1). Additional analyses were conducted for participants who completed all surveys.

Table 1
Table 1

Baseline characteristics of participants in a study of colds and influenza-like illnesses in students attending the Twin Cities campus of the University of Minnesota (Minneapolis-St. Paul), 2002–2003.

Among participants for whom complete data were available (n = 3249), the mean age was 22.9 years, 70.1% were female, 21.2% lived in a dormitory, 8.5% indicated that they had a past history of asthma, and 0.4% noted a past history of diabetes. Use of tobacco on at least 1 day during the month before completion of the baseline survey was reported by 19.1%, and 62.3% indicated that their health level was very good or excellent.

From November through April, 83.0% of respondents had ⩾1 cold, and 36.7% had ⩾1 ILI. In all, 91.0% of the participating students had at least 1 URI of either type. These URIs resulted in 6023 days in bed, 17,444 days with a significant decrease in the ability to perform daily activities, 4263 days of missed class, 3175 days of missed work, and 45,219 days of illness. They were also responsible for 17,371 h of missed extracurricular activities and 37,323 h of missed social activities over the 6-month period. Overall, 22.2% of the 3249 students had at least 1 visit to a health care professional because of a URI, 15.8% used antibiotics, and 74.9% used over-the-counter medications. A total of 40.5% of respondents missed at least 1 day of class, 27.8% reported doing poorly on a test because of their URI, and 46.3% did poorly on a class assignment.

The monthly rates of colds and ILIs and their effects on health care use and school life are summarized in table 2. ILIs had a greater impact on health care use and school life than did colds. In February, for example, persons with an ILI were more likely than persons with a cold to visit a health care professional (25.7% vs. 8.3%; P < .0001), to use antibiotics (13.8% vs. 6.1%; P < .0001), to use over-the-counter medications (86.5% vs. 62.2%, P < .0001), to miss class because of illness (61.6% vs. 30.0%; P < .0001), to do poorly on a test (33.7% vs. 16.9%; P < .0001), and to do poorly on a class assignment (55.8% vs. 37.9%; P < .0001).

Table 2
Table 2

Comparison of monthly health care use and impact on school life among students attending the Twin Cities campus of the University of Minnesota (Minneapolis-St. Paul) who had influenza-like illnesses (ILIs) or colds, 2002–2003.

ILIs resulted in a duration of symptoms that was longer and a degree of impairment that was greater than that for colds (table 3). Compared with persons with colds, persons with ILIs missed ∼3 times as many days of class and work and had ∼3 times as many days in bed, had ∼2 times the number of days with significant decrease in usual activities and hours of missed extracurricular and social activities, and had an illness duration that was ∼1.5 times longer. Both colds and ILIs were associated with a substantial decrement in overall general health status during the month of illness, but ILIs were associated with a larger decrease (table 4). In February, for example, the mean overall general health level (0, unsatisfactory; 1, satisfactory; 2, good; 3, very good; and 4, excellent) for volunteers with ILIs was only 1.18 (95% CI, 1.09–1.28), the mean level for those with colds was 1.96 (95% CI, 1.90–2.02), and the mean level for those with no URI was 3.20 (95% CI, 3.17–3.24).

Table 3
Table 3

Impact of influenza-like illnesses (ILIs) and colds on the functional status and quality of life of 3249 students attending the Twin Cities campus of the University of Minnesota (Minneapolis-St. Paul), 2002–2003.

Table 4
Table 4

General health level by type of illness among students at the Twin Cities campus of the University of Minnesota (Minneapolis-St. Paul) who had influenza-like illnesses (ILIs) or colds.

Symptoms from colds and ILIs that occurred in February 2003 are summarized in table 5. The prevalence of all listed symptoms was higher among students with ILIs. Similar differences in symptom rates were seen for the other study months (data not shown).

Table 5
Table 5

Symptoms reported by 362 students with influenza-like illnesses (ILIs) and 929 students with colds during February 2003, Twin Cities campus of the University of Minnesota (Minneapolis-St. Paul).

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Discussion

Colds and ILIs were common in our cohort, resulting in a substantial impact on the health and well-being of these university students. From November through April, 91% of students reported at least 1 URI, with 83% of the students having at least 1 cold and 36.7% having at least 1 ILI. These URIs were responsible for 6023 days in bed, 4263 days of missed class, 3175 days of missed work, and 45,219 days of illness among the 3249 students in the cohort.

Previous studies involving younger adult populations have generally focused on working adults. In such studies, the indirect costs associated with illness have been prominent [4, 5, 10–16]. These studies have consistently found that upper respiratory tract infections, including influenza and the common cold, are associated with substantial rates of work loss [4, 5, 10–16]. URIs can also reduce one's effectiveness at work, including subjective alertness and psychomotor functioning [17, 18], and influenza has been shown to impair the ability to perform reaction-time tasks to a degree similar to that associated with working at night or alcohol consumption [19]. In 1 study, 88% of workers with colds reported a mean decrease of 21.2% in work effectiveness [5]. In another study of employees with ILIs, subjects reported a level of work effectiveness of 4.6 on a scale of 1 (low effectiveness) to 10 (normal effectiveness) [20]. Together, these studies demonstrate the importance of impaired productivity for understanding the indirect costs associated with URIs. In fact, the indirect costs associated with these illnesses, including both work loss and reduced work productivity, represent more than one-half of all societal costs for these illnesses [4, 5, 12–15].

Our study provides additional information specifically on the consequences of colds and ILIs among university students. In our cohort, 69.7% of the students worked a median of 18 h per week. Participants with colds missed a mean of 0.24–0.34 days of work, whereas those with ILIs missed 0.77–1.01 days of work. The economic consequences of missed days of work likely were felt both by the employers, who had to accommodate unexpected employee absences, and by the students, who, as part-time workers, probably did not qualify for paid sick leave. (In 1999, a total of 63% of full-time and 19% of part-time US workers in nongovernment jobs received paid sick-leave benefits [21].) The indirect costs associated with illness also extended to school absenteeism and to impaired levels of academic performance. Study participants missed 0.43–0.56 day of class with colds and 1.24–1.74 days of class with ILIs. In addition, 14.5%–17.3% of students with colds did poorly on a test and 33.6%–38.0% did poorly on a class assignment, whereas 29.4%–40.5% of students with ILIs did poorly on a test and 54.4%–57.7% did poorly on a class assignment. Although we did not estimate the economic cost of the value that students placed on avoiding a day of missed class or impaired school performance, our findings suggest that class attendance and academic performance are important outcome and indirect cost parameters that should be included in studies of URIs among college students.

Leisure-time activities were also affected by URIs. Students with colds missed 1.52–1.94 h of extracurricular activities and 3.53–4.05 h of social activities per illness, whereas students with ILIs missed 3.41–5.03 h of extracurricular activities and 7.74–10.12 h of social activities. Elsewhere, 84% of workers with an ILI reported interference with leisure-time activities [20].

Reductions in general health were also seen with URIs, further highlighting the impact of these illnesses on overall well-being. General health scores for respondents with ILIs were reduced by approximately one-half, whereas scores for those with colds were reduced by approximately one-third. Other investigators have also found that health-related quality of life is substantially reduced for persons with URIs and persons with influenza. In 1 study, mean health utility scores for healthy adults with influenza ranged from 0.4 on day 1 of illness to 0.79 on day 7 of illness (0, worst possible health; and 1, normal health) [22]. Another study of influenza symptoms suggested a mean utility for influenza of 0.25 (0, state of death; and 1, state of perfect health) [23]. Researchers investigating the health-related quality of life for persons with URIs also found decrements in health-related quality of life that were similar in magnitude to those seen for adults with chronic diseases, such as lung disease, osteoarthritis, and depression [24]. Our findings, together with the results of these other studies, provide important insights regarding the impact of URIs on people's lives and the potential value of prevention and treatment.

In addition to these less direct measures of the costs and implications of URIs, increased medical care use was also associated with URIs. Overall, 22.2% of the students in the cohort visited a health care professional because of their illness, and 15.8% received antibiotics. Other investigators have reported frequent use of antibiotics among persons with URIs, despite the fact that nearly all URIs are of viral origin [4, 5, 25–29]. The reasons for overprescription of antibiotics might include the clinicians' desire to meet their patients' expectations for receiving antibiotics [30]. Given concerns about increasing antimicrobial resistance [31], our findings suggest that college students and their health care professionals should be educated about the appropriate indications for and use of antibiotics.

Although uncommon, serious complications resulting in hospitalization can also occur with URIs. In our cohort, there was a trend toward higher rates of hospitalization among participants with ILIs versus colds: 0.9% of students with URIs were hospitalized, with rates for students with ILIs 2–10 times those for students with colds (table 2). This rate of hospitalization is similar to the 0.8% rate reported for healthy adults with confirmed influenza [32].

Colds were more common in our cohort, but ILIs had a greater impact per illness. Many ILIs occurred during the influenza season and therefore likely represented genuine influenza illnesses. The 2002–2003 influenza season in Minnesota extended from January through April [33]. Over this period, 27.9% of the students reported at least 1 episode of ILI. These students missed 1406 days of class and 1000 days of work, were in bed for 2043 days, and were sick for 9478 days. of the students who had ILIs, 29.3% sought medical care, and 17.3% received antibiotics (data not shown). Thus, ILIs during the 4-month influenza season accounted for a substantial amount of the total URI disease burden in this study. In a pooled analysis of data from clinical trials assessing the effectiveness of zanamivir treatment for influenza in healthy young adults, the positive predictive value of fever and cough for laboratory-confirmed influenza when influenza viruses are circulating in the community was 79% [34]. Thus, up to 22.3% of students in our cohort may have developed influenza during the influenza season.

College and university students are not among the high-priority groups for routine influenza vaccination in the United States [35], and it is likely that current vaccination rates in this group are low. Previous studies have generally suggested that vaccination against influenza is highly cost-effective and even cost-saving for healthy working adults [12, 36], and the use of antivirals for the treatment of influenza might also be cost-effective [14–16, 22, 23]. Nationally, <20% of persons 18–34 years of age have been vaccinated [37]. We did not obtain reliable information about influenza vaccination for our cohort because of a survey construction error, but data from the student health service suggest that vaccination rates among our participants were probably low. Only 3314 vaccinations were administered to the 42,000 University of Minnesota students during the 2002–2003 season (E. Ehlinger, unpublished observations). The use of antivirals was also undoubtedly low in our cohort. We did not include questions about antivirals in our surveys, but <35 prescriptions for antiviral medications for influenza were dispensed from the student health service during the 2002–2003 season (E. Ehlinger, unpublished observations). Increased use of vaccination and antiviral therapy might be cost-effective strategies for improving the health of these students.

Several potential limitations of our study deserve comment. Our data were based on self-report. Self-report has previously been shown to be reliable for assessing infectious illness symptoms, including URIs, even with a 3-month recall period [38]. Nevertheless, self-report may have led to inaccurate reporting of illness in our study. We also did not collect information about use of antivirals, and some of the participants may have confused antivirals with antibiotics in their survey responses. However, very few antiviral prescriptions were dispensed from the student health service during the 2002–2003 season, and it is unlikely that any misclassification of antivirals as antibiotics significantly affected our findings. The reported rates of antibiotic use in our study are also similar to those in other studies. Incomplete follow-up data may also have biased our results. Our main analyses included only participants who finished all of the surveys. However, the students for whom we had complete follow-up data appeared to have baseline characteristics similar to those of the entire group of volunteers (table 1). Furthermore, the monthly illness rates for all respondents in a given month were virtually identical to those for participants who responded to all surveys (data not shown). Thus, we believe that our results reflect the experience of our entire cohort. Another question is whether the results are generalizable to other populations. Our participants were somewhat younger (mean age, 22.9 vs. 25.0 years) and more likely to be female (70.1% vs. 53%), compared with all students at the Twin Cities campus of the University of Minnesota [39]. However, the percentages of participants with diabetes, asthma, and excellent or very good health at baseline were similar to the percentages for the general population aged 18–24 years (0.4% vs. 0.7%, 8.5% vs. 8.9%, and 62.3% vs. 62.4%, respectively) [37]. The rates of illness, duration of illness, and health care use among our participants were also consistent with rates reported in other studies. Although our results should be interpreted with some caution, we do believe that they are relevant to other university and college student populations.

Colds and ILIs were frequent and associated with significant effects on health, school and work performance, leisure time activities, and health care use in our study. Influenza viruses may cause up to 30% of URIs for which a viral agent is recovered [1], and they are the only common agents for which infection can be prevented or controlled through vaccination and/or antiviral therapy. Until new vaccines and antivirals are available for other agents that cause URIs, enhanced efforts for the prevention and control of influenza through vaccination and judicious use of antiviral therapy, coupled with more effective application of general infection-control measures (such as good hand hygiene) could go a long way toward improving the health and well-being of the 17 million college and university students in this country [40].

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Acknowledgments

Financial support. This was an investigator-initiated study that was supported by unrestricted grants from Aventis Pasteur and MedImmune. The study sponsors reviewed the proposed study design before providing funding and had an opportunity to review the manuscript before it was submitted, but they did not otherwise participate in the design or conduct of the study; in the collection, management, analysis, or interpretation of the study data; or in the preparation or approval of the manuscript.

Potential conflicts of interest. K.L.N. has previously received research funding from Aventis Pasteur. S.D. and E.E.: no conflicts.

  • Received August 17, 2004.
  • Accepted December 19, 2004.
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  1. Clin Infect Dis. (2005) 40 (9): 1263-1270. doi: 10.1086/429237
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