Health Outcomes of Patients Previously Treated for Lyme Disease

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The summary below is from the full report titled "Musculoskeletal and Neurologic Outcomes in Patients with Previously Treated Lyme Disease." It is in the 12 December 1999 issue of Annals of Internal Medicine (volume 131, pages 919-926). The authors are N.A. Shadick, C.B. Phillips, O. Sangha, E.L. Logigian, R.F. Kaplan, E.A. Wright, A.H. Fossel, K. Fossel, V. Berardi, R.A. Lew, and M.H. Liang.

What is the problem and what is known about it so far?

Lyme disease is an infection caused by a bacterium carried by ticks. Some people worry that health problems, including arthritis, tiredness, mood disturbances, and memory disturbances, can develop in the years after the infection, even when patients were properly treated with antibiotics. However, few studies have looked to see how often these same problems are found in people without past Lyme disease compared with those who did have the disease.

Why did the researchers do this particular study?

To find out whether people who had Lyme disease in the past had more health problems than a comparison group of people who never had that infection.

Who was studied?

Lyme disease is very common on Nantucket Island in Massachusetts. The researchers studied 186 people who lived on that island between January 1993 and January 1996 and had previously received treatment for Lyme disease. Treatment had been given an average of about 6 years before the study. The researchers also studied 167 people from the island whose age and sex were similar to those of the Lyme disease patients but who had never had Lyme disease (the control group).

How was the study done?

The researchers evaluated the health of both the Lyme disease and control groups in several ways. First, they asked detailed questions about physical and psychological symptoms, physical function, and past and present illnesses. Second, they performed a detailed physical examination of the joints, muscle strength, and sensation. Finally, they carried out formal tests of memory, manual dexterity, ability to learn, and ability to concentrate.

What did the researchers find?

Persons who had been treated for Lyme disease were more likely than controls to report symptoms of joint pain, memory difficulties, and pain that limited their activities. However, the physical examination revealed no differences between the two groups. Similarly, patients with past Lyme disease performed just as well as those who had never had Lyme disease on all of the neurologic and mental tests.

What were the limitations of the study?

The researchers had to rely on past diagnoses of Lyme disease since they did this study a number of years after patients had been treated. Also, people who had previous Lyme disease could have overreported symptoms, given their knowledge about the possible long-term effects of this disease. However, overreporting would not influence the more objective findings on physical examination and formal testing.

What are the implications of the study?

People who have been treated for Lyme disease may be more likely to experience joint pain, memory problems, and difficulty with activities due to pain than people who have not. However, patients previously treated for Lyme disease do not appear to have more physical evidence of arthritis or measurable problems with mental or neurologic function.