Direct Medical Costs
Table summarizes annual healthcare expenditures for individuals classified as CFS, ISF, and NF. For comparison, we have also reported healthcare expenditures for the U.S. population age 18 to 59, calculated from the 2005 MEP Survey. Healthcare expenditures for the Georgia sample ($2,767) were, on average, not greatly different from those reported by similarly aged US adults ($2,963), as estimated in the 2005 MEP Survey.
Mean Annual Healthcare Expenditures of the Sampled Population, with Comparisons to the Non-elderly US Population (in US Dollars, $)
Individuals with CFS reported significantly higher healthcare expenditures, in total and separately in all utilization categories. Mean expenditures for persons with CFS were $5,683, almost double the mean costs reported by the ISF sample ($2,968) and 170% higher than NF ($2,096).
Table summarizes the adjusted results from Linear OLS, Log OLS, GLM, and TPM for each category of healthcare expenditure. The incremental total expenditures attributed to CFS estimated from the GLM gamma with a log link function ($3,286) was less than 10% relative difference from untransformed Linear OLS ($3,085) and TPM ($3,618). The -2 log-likelihood for the TPM on total expenditures was 8214.72, smaller than that for the GLM (8647.42). However, AIC penalized the two-part model (13-54 folds) and Linear OLS (460-2373 folds) for its additional parameters for each category of healthcare expenditure. Thus, we selected the results from GLM for inferences in this paper.
Estimated Regression-adjusted Effect of CFS and ISF on Annual Healthcare Expenditures (in US Dollars, $)
Paralleling prior research, age, sex, and race/ethnicity contributed significantly to healthcare expenditures in the GLM models, reported in full (Additional file 2
, Table S2). Adjusting for covariates, those with CFS spent $3,286 more annually compared to NF (p = 0.001). Similarly, those classified as ISF spent $1,058, more annually than NF (p = 0.003). Adjusted estimates were slightly greater than the unadjusted estimates presented in Table , above.
Examining the pattern of expenditures helps us understand how individuals with fatiguing illness interact with the healthcare system for prevention, ambulatory care and treatment of acute conditions requiring hospitalizations. Provider visits accounted for the largest share (41%) of incremental CFS costs. Compared to NF, individuals with CFS diagnoses annually incurred an additional $1,343 (p = 0.022) for costs related to ambulatory healthcare visits (physician, dentist, nurse practitioner, therapist, chiropractor, etc). Prescription drugs were the next largest driver (38%) of additional healthcare costs for the CFS sample. Individuals with CFS spent $1,241 (p = 0.074) more on prescription drugs annually than comparable non-fatigued patients. CFS patients also spent more on over-the-counter medications ($204, p = 0.066). Hospitalization for the CFS sample is an infrequent event. While those with CFS exhibit slightly higher expenses when hospitalized, their hospitalization rate was not significantly greater than the non-fatigued sample. Hence, inpatient costs were not statistically significantly raised for those with CFS.
ISF patients had healthcare utilization and cost profiles that fell between the NF samples and the CFS samples: ISF raised healthcare cost by over $1,058 annually (p = 0.01). The largest portion (30%) of the incremental cost of ISF was attributed to prescription medications, which increased by $317 per year relative to controls (p = 0.016). Costs for ambulatory care were also higher in the ISF sample, but not statistically significantly so.
Out of pocket costs are often the best measure of the direct financial burden faced by patients. CFS raised patients' total out-of-pocket (OOP) expenditures by $947 per year relative to the NF sample (p = 0.003, GLM results in Table ). Increases in prescription medication costs, provider visit costs, and over-the-counter medication purchases represented 83%, 29% and 22% (respectively) annual out-of-pocket cost burden attributed to CFS. We estimated out-of-pocket costs for the ISF sample to be $482 higher than NF (p < 0.001). As with total expenditures, prescription medications were the largest portion of the incremental out-of-pocket costs for ISF.
Estimated regression-adjusted effect of CFS and ISF on annual out-of-pocket healthcare expenditures (in US Dollars, $)
A person's educational attainment is an important determinant of their earnings. Fifteen percent of the CFS sample experienced onset of CFS in their teens and early twenties, and had significantly lower educational attainment than others whose CFS symptoms developed later in life. In particular, the early-onset CFS sample had much lower rates of college and post-graduate education, with the expected adverse effect on their employment and earnings. College-educated individuals who were not fatigued earned $18,899 more annually than individuals with CFS who did not earn a college degree (p < 0.01; data statistics not shown).
To assess the impact of CFS on education, we modeled college graduation rates among CFS cases as a function of age, race, geographic location, sex, marital status, and age of CFS onset. After adjusting for demographic covariates, for individuals with known CFS at age 24 or earlier, the predicted percentage who would have finished college more than doubles (rises from 23% to 57%) when CFS onset is moved to after age 24 (p < 0.01, Table ).
Age of CFS Onset and Educational Attainment (Finishing College) in the Sampled Population
Age of illness onset was unknown for 32% of the CFS sample and only 8% of those with missing onset data had graduated from college. Had these individuals experienced CFS onset at or after age 25, our model predicted that 34% would have completed college (p < 0.01).
We used our education attainment models to predict a counter-factual level of education for those with early onset CFS. Predicted education was used as a covariate in place of observed education of our earnings and employment analyses. By comparing the two model specifications - with observed versus predicted education -- we observed how much of the impact of CFS on earnings is attributable to lower educational attainment.
Earnings and Employment
Persons with CFS earned $23,076 annually and 71% had been employed within the past 4 weeks (Table ). These figures compare unfavorably to the NF sample who reported mean annual earnings of $33,888 and a 95% rate of employment over the 4 weeks prior to the survey.
Table summarizes the estimated effects of CFS on employment and earnings over a 4-week period, after adjusting for covariates. This table provides the odds ratios (OR) of employment for the CFS (or ISF) sample relative to NF and incremental effects of CFS on earnings from the results of Linear OLS, GLM, and a two-part model (the first part using a logistic regression for binary indicator for having earnings and the second part using GLM for non-zero earnings). The results of full GLM and logistic models were reported in Additional file 2
, Table S3.
Impact of Fatigue on Employment and Earnings
CFS and ISF each had a negative impact on earnings and on labor force participation. The model utilizing imputed educational attainment estimated a $658 reduction in 4-week earnings associated with CFS (compared to NF).
When we used reported educational attainment in the model, the effect of CFS on earnings falls to $503 per four-week period. The 24% reduction in the "CFS effect" was because the reported education specification ignored the downward bias in educational attainment that resulted from early-onset of fatigue. Because our sample was all working-age, this change was relative to a very high employment rate (95%) among well individuals. Decreasing the probability of employment by 19 percentage points in the NF group (all else being equal) would reduce average monthly earnings per person by about $330--about half of the total CFS effect on earnings (data statistics not shown in the table). Individuals with CFS were also significantly less likely than NF to have worked in the past 4 weeks (odds-ratio = 0.12, p = 0.001).
Turning to the results for the ISF sample, ISF significantly reduced the likelihood of working during the past 4 weeks. Although the point estimate on earnings suggests a negative effect as well, the estimate is not statistically significant. For examining the impact of CFS on earnings, Additional file 2
, Table S4 summarizes its impact on earning controlling separately for the interaction with the reported educational attainment and the employment status. Compared to NF with BA or post graduate degree, CFS subjects without and without BA or post graduate degree had $1,320 and 611 less annual earnings, respectively. In a separate analysis controlling for the interaction of CFS and the employment status, unemployed and employed CFS subjects had $574 and 40 less annual earnings than employed NF subjects.
The combined economic burden of CFS, including both direct and indirect annualized costs, was $11,780; representing $3,226 in direct medical costs (Table ) and $8,554 in lost earnings (Table ). The estimate was approximately $2,015 lower using the specification that ignored the effect of illness on education.