IN 1992-1993, approximately 2,900 Dutch military personnel participated in the peacekeeping operation, United Nations Transitional Authority for Cambodia (UNTAC), for 6 mo. Following their return to the Netherlands, some of these personnel complained of persistent fatigue, inability to concentrate, and memory loss--symptoms virtually identical to those in Gulf War-related illnesses. (1,2) From the time of the American Civil War, unexplained symptoms in military personnel have been the subject of considerable interest. (3,4) Fatigue, headache, difficulty concentrating, shortness of breath, diarrhea, and muscle/joint pains have been prominent complaints. Several somatic hypotheses, among which is exposure to toxic substances, have been suggested as possible explanations for these various war syndromes. (4)

Gulf War-related illness has been defined in the context of Multiple Chemical Sensitivity (MCS) Syndrome. (5,6) MCS Syndrome was initially described by Randolph more than 40 yr ago, (7) but its existence remains controversial. According to a recent consensus among the proponents of MCS Syndrome, it is a chronic condition with symptoms in multiple organ systems. The symptoms occur in response to low levels of exposure to multiple unrelated chemicals, and they improve or resolve when the incitants are removed. (8)

According to Miller, (9) a 2-step process occurs in MCS Syndrome: (1) an initial exposure, (2) followed by a loss of tolerance for formerly well-tolerated substances. An initial exposure can be a one-time, intermittent, or continuous exposure to pesticides or solvents. Miller (9) suggested that the phrase "toxicant-induced loss of tolerance" more fully describes the process, whereas chemical sensitivity may be its consequence.

In the present study, we retrospectively evaluated self-reported chemical exposures in symptomatic Dutch Cambodia veterans before, during, and after the UNTAC mission. A postal questionnaire was used to determine whether the veterans fulfilled the MCS Syndrome criteria. We then compared their results with a well-matched control group of healthy Dutch Cambodia veterans. Matching criteria were: sex; age; military branch and rank during UNTAC; and, if known, geographical area of current residence in The Netherlands.

Method

Patients. This study of MCS Syndrome in symptomatic Cambodia veterans was part of a follow-up study conducted 18 mo after an initial assessment. In the initial assessment, (1) a postal questionnaire was sent to all Dutch Cambodia veterans whose addresses could be retrieved from the database of the Ministry of Defense (n = 2,548 [97.4% of the entire Dutch Cambodia veteran population]). The survey contained questions about severity of fatigue (i.e., the Checklist of Individual Strength [CIS] (10) was incorporated) and other self-reported symptoms, but contained no questions specifically about MCS Syndrome. A total of 1,721 (68%) male veterans responded to the questionnaire. Details of this study, in which the prevalence of symptoms was investigated, are provided elsewhere. (1)

Eighteen months after the initial assessment, a follow-up questionnaire was sent regarding severity of fatigue (i.e., the CIS), self-reported improvement, and self-efficacy, to a subgroup of the initial study subjects: 354 veterans who (a) had given permission for follow-up and (b) met our case definition for symptoms in Cambodia veterans (i.e., a score of [greater than or equal to] 37 on the fatigue severity subscale of the CIS at initial assessment). To ensure that borderline cases were identified, veterans who had sub-threshold scores (i.e., CIS fatigue severity score [greater than or equal to] 32 and < 37) at initial assessment were also provided with a follow-up questionnaire. (2) However, it appeared that, 18 mo after initial assessment, only 105 Cambodia veterans had CIS scores that met our case definition. These subjects did not differ in age, education, military rank, or initial fatigue severity from the 249 veterans who did not fulfill the case definition after 18 mo had elapsed. (2)

We invited the abovementioned 105 veterans, by telephone, to participate in an individual assessment program at our outpatient clinic. The assessment program comprised psychological interviews; neurological interviews; questionnaires about depression, physical activity, self-esteem, and personality disorders; general and neurological physical examinations; and immunological and microbiological laboratory investigations. Twenty-four veterans were unwilling or unable to attend our clinic; therefore, 81 veterans participated in the study. For the present study, these 81 veterans received an additional questionnaire regarding toxic exposures to organic solvents or insecticides during work tasks and in their living areas. Seventy-seven persons completed the questionnaire, of which only male (n = 76) symptomatic veterans were included in our analyses. Although an additional 4 persons participated in the individual assessment program, they were not willing to complete the questionnaire with respect to toxic exposures, citing its length and the detailed nature of the questions. With respect to the 76 male veterans who participated in our study and the 29 who did not participate, there were no differences in demographics (e.g., age, education, military rank, initial fatigue score).