Methods: 194 subjects answered a binary (yes-no) questionnaire (Simon GE et al, 1993) to determine if “medications” (not further subdivided by drug class) caused any of 25 symptoms from the neurological (6 symptoms); musculoskeletal (5); airways (7); gastrointestinal (5); and skin (2) systems. Subjects used our CFS Severity score to estimate the severity of fatigue and the 8 minor criteria for the previous 6 months.
Results: The subgroup of ALL CFS females had more frequent nausea (32% vs. 13%; p=0.013) and visual changes (19% vs. 4%; p=0.018) than ALL non-CFS females. ALL CFS males had nausea (26%; p=0.003) and dizziness (23%; p=0.006) compared to zero in ALL non-CFS males. However, these differences were misleading because many individuals had no symptoms, and so would not have adverse complaints or contact their physicians. Therefore, the 47% of CFS and 72% of non-CFS subjects with zero symptoms were removed.
The remaining 65 CFS subjects had 5.6 symptoms (4.2 to 7.0, 95% CI). The 20 non-CFS subjects had 3.5 symptoms (1.8 to 5.2; not significant by t-test). Females in these subsets had no significant differences in symptoms frequencies. However, CFS males (n = 22) had more nausea (54.5% vs. 0%; p=0.067) and dizziness (50% vs. 0%; p=0.091) for non-CFS males (n = 4).
Conclusions: The apparent higher prevalence of medication-related symptoms in CFS than non-CFS was biased by the large number of subjects with zero symptoms. When subjects with no complaints were excluded, there was no difference between CFS and non-CFS females, but a trend for CFS males to have had more gastrointestinal and neurologic symptoms than the non-CFS males. Overall, the equivalence of symptoms in CFS and non-CFS suggests that Multiple Chemical Sensitivity (MCS) may be an independent syndrome. These methods will direct our analysis of other irritants in this multiple chemical sensitivity questionnaire.