BACKGROUND: Lyme disease is the most common vector-borne illness diagnosed in the United States. Following a period of latent infection, long-term sequelae of untreated disease may involve the neurologic, cardiac, and musculoskeletal systems. Diagnosis is often difficult, as serologic testing is not standardized and patients with early disease may be antibody-negative. Vaccination confuses the issue by converting patients to seropositivity but protecting only 76% against symptomatic Lyme disease.1 Because it is primarily a clinical diagnosis, there are concerns about inadequate detection and treatment resulting in insidious progression of symptoms. Additionally, concern has been raised regarding possible long-term sequelae of the disease despite accepted treatment.
POPULATION STUDIED: Of the 8764 suspected cases of Lyme disease reported to the Connecticut Department of Public Health between 1984 and 1991, 1325 patients were randomly selected and 678 were included in this study. Of these, 52% were female, 34% were children, and 99% were white. The median age was 36 years. Patients were excluded if they reported that they had never had Lyme disease, did not speak English, or did not reside in Connecticut at the time of diagnosis.
STUDY DESIGN AND VALIDITY: This 2-part study consisted of a prospective longitudinal study and a case-control substudy to determine the frequency of long-term symptoms. In the longitudinal group, the median time from diagnosis was 51 months (range=15-135 months). A random subsample of 212 patients was selected from the longitudinal study. These patients were matched and compared with a person without Lyme disease of similar age and area of residence (control group). Patients and control subjects were interviewed by telephone using a standardized questionnaire to evaluate increased frequency of symptoms and increased difficulty in ability to perform activities. Adults also completed a study of general health and well-being (the Medical Outcomes Study Short Form-36 [SF-36]) and the Center for Epidemiologic Studies-Depression (CES-D) questionnaire. Parents were interviewed if the patient was a child.
OUTCOMES MEASURED: The primary outcome was a change in frequency of specifically identified symptoms and ability to perform certain typical daily activities. Patients were also screened for depression, and their health-related quality of life was evaluated.
RESULTS: Of patients with Lyme disease, 69% reported an increase in symptoms and difficulty with daily activities. Patients who did not meet the case definition for Lyme disease were significantly more likely to report joint or muscle pain (relative risk [RR]= 0.71; 95% CI, 0.57-0.88), numbness (RR=0.65; 95% CI, 0.48-0.88), fatigue (RR=0.66; 95% CI, 0.48-0.89), and headaches (RR=0.67; 95% CI, 0.47-0.96). Symptom reports were similar when patients were stratified by whether they had received antibiotic therapy, with the exception of joint or muscle aches, which were reported less often in the antibiotic-treated patients (RR=0.71; 95% CI, 0.6-0.9). Comparing patients with a diagnosis of Lyme disease with their matched control subjects, only joint or muscle pain (RR=1.4; 95% CI, 1.03-1.89) and difficulty formulating ideas (RR=2.96; 95% CI, 1.36-6.43) were reported more frequently. There were no statistically significant differences in the health and well-being (SF-36) and depression (CES-D) scores among the longitudinal and matched cohorts.
It appears that long-term outcomes are good in patients with Lyme disease when it is correctly diagnosed and treated. Long-term symptoms were more likely to be reported by patients who were given a diagnosis of Lyme disease but did not meet the CDC definition for diagnosis. It is uncertain whether these patients had an atypical presentation of Lyme disease or another chronic disease.