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Chronic Fatigue Syndrome and High Allostatic Load: Results From a Population-Based Case-Control Study in Georgia

From the Chronic Viral Diseases Branch (E.M.M., R.B., W.C.R.), National Center for Zoonotic, Vector-borne and Enteric Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; and the Department of Psychiatry and Behavioral Sciences (U.M.N.), Emory University School of Medicine, Atlanta, Georgia.

Address correspondence and reprint requests to Elizabeth M. Maloney, Centers for Disease Control and Prevention, 1600 Clifton Road, MS A-15, Atlanta, GA 30333. E-mail: evm3{at}cdc.gov

Objective: To confirm the association of chronic fatigue syndrome (CFS) with high allostatic load (AL) level, examine the association of subsyndromal CFS with AL level, and investigate the effect of depression on these relationships and the association of AL with functional impairment, fatigue, symptom severity, fatigue duration, and type of CFS onset. AL represents the cumulative physiologic effect of demands to adapt to stress.

Methods: Population-based case-control study of 83 persons with CFS, 202 persons with insufficient symptoms or fatigue for CFS (ISF), and 109 well controls living in Georgia. Unconditional logistic regression was used to generate odds ratios (ORs) as measures of the association of AL with CFS.

Results: Relative to well controls, each 1-point increase in allostatic load index (ALI) was associated with a 26% increase in likelihood of having CFS (OR_adjusted = 1.26, 95% Confidence Interval (CI) = 1.00, 1.59). This association remained in the presence and absence of depression (OR_adjusted = 1.35, CI = 1.07, 1.72; OR_adjusted = 1.35, CI = 1.10, 1.65). Compared with the ISF group, each 1-point increase in ALI was associated with a 10% increase in likelihood of having CFS (OR_adjusted = 1.10, CI = 0.93, 1.31). Among persons with CFS, the duration of fatigue was inversely correlated with ALI (r = –.26, p = .047).

Conclusions: Compared with well controls, persons with CFS were significantly more likely to have a high AL. AL increased in a gradient across well, ISF, and CFS groups.

Key Words: CFS • allostatic load • case-control • population-based • Georgia • SF-36

Abbreviations: CFS = chronic fatigue syndrome; ISF = insufficient symptoms or fatigue for CFS; AL = allostatic load; ALI = allostatic load index; BMI = body mass index; HPA = hypothalamic-pituitary-adrenal; CDC = Centers for Disease Control and Prevention; SF-36 = Medical Outcomes Survey Short Form-36; MFI = Multidimensional Fatigue Inventory; CRP = C-reactive protein; HDL = high-density lipoprotein; AUC = area under the curve; OR = odds ratio; CI = Confidence Interval; HL = Hosmer-Lemeshow.