Tamara B. Harris

Associations of elevated interleukin-6 and C-reactive protein levels with mortality in the elderly.

PURPOSEnTo investigate whether interleukin-6 and C-reactive protein levels predict all-cause and cause-specific mortality in a population-based sample of nondisabled older people.nnnSUBJECTS AND METHODSnA sample of 1,293 healthy, nondisabled participants in the Iowa 65+ Rural Health Study was followed prospectively for a mean of 4.6 years. Plasma interleukin-6 and C-reactive protein levels were measured in specimens obtained from 1987 to 1989.nnnRESULTSnHigher interleukin-6 levels were associated with a twofold greater risk of death [relative risk (RR) for the highest quartile (> or = 3.19 pg/mL) compared with the lowest quartile of 1.9 [95% confidence interval, CI, 1.2 to 3.1]). Higher C-reactive protein levels (> or = 2.78 mg/L) were also associated with increased risk (RR = 1.6; CI, 1.0 to 2.6). Subjects with elevation of both interleukin-6 and C-reactive protein levels were 2.6 times more likely (CI, 1.6 to 4.3) to die during follow-up than those with low levels of both measurements. Similar results were found for cardiovascular and noncardiovascular causes of death, as well as when subjects were stratified by sex, smoking status, and prior cardiovascular disease, and for both early (<2.3 years) and later follow-up. Results were independent of age, sex, body mass index, and history of smoking, diabetes, and cardiovascular disease, as well as known indicators of inflammation including fibrinogen and albumin levels and white blood cell count.nnnCONCLUSIONSnHigher circulating levels of interleukin-6 and C-reactive protein were associated with mortality in this population-based sample of healthy older persons. These measures may be useful for identification of high-risk subgroups for anti-inflammatory interventions.

Inflammatory Markers and Onset of Cardiovascular Events Results From the Health ABC Study

Background—Inflammation plays an important role in cardiovascular disease. The aim of this study is to investigate the predictive value of several inflammatory markers on the incidence of cardiovascular events in well-functioning older persons. Methods and Results—The subjects were 2225 participants 70 to 79 years old, without baseline cardiovascular disease, who were enrolled in the Health, Aging, and Body Composition study. Incident coronary heart disease (CHD), stroke, and congestive heart failure (CHF) events were detected during an average follow-up of 3.6 years. Blood levels of interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor-&agr; (TNF-&agr;) were assessed. After adjustment for potential confounders, IL-6 was significantly associated with all outcomes (CHD events, per IL-6 SD increase: RR, 1.27; 95% CI, 1.10 to 1.48; stroke events, per IL-6 SD increase: RR, 1.45; 95% CI, 1.12 to 1.86; CHF events, per IL-6 SD increase: RR, 1.72; 95% CI, 1.40 to 2.12). TNF-&agr; showed significant associations with CHD (per TNF-&agr; SD increase: RR, 1.22; 95% CI, 1.04 to 1.43) and CHF (per TNF-&agr; SD increase: RR, 1.59; 95% CI, 1.30 to 1.95) events. CRP was significantly associated with CHF events (per CRP SD increase: RR, 1.48; 95% CI, 1.23 to 1.78). A composite summary indicator of inflammation showed a strong association with incident cardiovascular events, with an especially high risk if all 3 inflammatory markers were in the highest tertile. Conclusions—Findings suggest that inflammatory markers are independent predictors of cardiovascular events in older persons.

Serum IL-6 level and the development of disability in older persons

BACKGROUND: The serum concentration of interleukin 6 (IL‐6), a cytokine that plays a central role in inflammation, increases with age. Because inflammation is a component of many age‐associated chronic diseases, which often cause disability, high circulating levels of IL‐6 may contribute to functional decline in old age. We tested the hypothesis that high levels of IL‐6 predict future disability in older persons who are not disabled.

Inflammatory markers and cognition in well-functioning African-American and white elders

Background: Several lines of evidence suggest that inflammatory mechanisms contribute to AD. Objective: To examine whether several markers of inflammation are associated with cognitive decline in African-American and white well-functioning elders. Methods: The authors studied 3,031 African-American and white men and women (mean age 74 years) enrolled in the Health, Aging, and Body Composition Study. Serum levels of interleukin-6 (IL-6) and C-reactive protein (CRP) and plasma levels of tumor necrosis factor-α (TNFα) were measured at baseline; cognition was assessed with the Modified Mini-Mental State Examination (3MS) at baseline and at follow-up. Cognitive decline was defined as a decline of >5 points. Results: In age-adjusted analyses, participants in the highest tertile of IL-6 or CRP performed nearly 2 points lower (worse) on baseline and follow-up 3MS (p < 0.001 for all) and declined by almost 1 point over the >2 years (p = 0.01 for IL-6 and p = 0.04 for CRP) compared with those in the lowest tertile. After multivariate adjustment, 3MS scores among participants in the highest tertile of IL-6 and CRP were similar at baseline but remained significantly lower at follow-up (p ≤ 0.05 for both). Those in the highest inflammatory marker tertile were also more likely to have cognitive decline compared with the lowest tertile for IL-6 (26 vs 20%; age-adjusted odds ratio [OR] = 1.34; 95% CI 1.06 to 1.69) and for CRP (24 vs 19%; OR = 1.41; 95% CI 1.10 to 1.79) but not for TNFα (23 vs 21%; OR = 1.12; 95% CI 0.88 to 1.43). There was no significant interaction between race and inflammatory marker or between nonsteroidal anti-inflammatory drug use and inflammatory marker on cognition. Conclusions: Serum markers of inflammation, especially IL-6 and CRP, are prospectively associated with cognitive decline in well-functioning elders. These findings support the hypothesis that inflammation contributes to cognitive decline in the elderly.

Inflammatory Markers and Risk of Heart Failure in Elderly Subjects Without Prior Myocardial Infarction

Background—Experimental studies support a key role for cytokines in left ventricular remodeling. In congestive heart failure (CHF) patients, elevated plasma cytokine levels are associated with worse functional status and adverse prognosis. It is unclear whether cytokine levels can predict the incidence of CHF in asymptomatic individuals. Methods and Results—We investigated the relations of serum interleukin-6 (IL-6), C-reactive protein (CRP), and spontaneous production of tumor necrosis factor-&agr; (TNF&agr;) by peripheral blood mononuclear cell (PBMC) to CHF incidence among 732 elderly Framingham Study subjects (mean age 78 years, 67% women) free of prior myocardial infarction and CHF. On follow-up (mean 5.2 years), 56 subjects (35 women) developed CHF. After adjustment for established risk factors, including the occurrence of myocardial infarction on follow-up, there was a 60 (PBMC TNF&agr;) to 68% (serum IL-6) increase in risk of CHF per tertile increment in cytokine concentration (P =0.04, and 0.03, respectively, for trend). A serum CRP level ≥5 mg/dL was associated with a 2.8-fold increased risk of CHF (P =0.02). Subjects with elevated levels of all 3 biomarkers (serum IL-6 and PBMC TNF&agr; >median values, CRP≥5 mg/dL) had a markedly increased risk of CHF (hazards ratio 4.07 [95% CI 1.34 to 12.37], P =0.01) compared with the other subjects. Conclusions—In our elderly, community-based sample, a single determination of serum inflammatory markers, particularly elevated IL-6, was associated with increased risk of CHF in people without prior myocardial infarction. Additional epidemiological investigations are warranted to confirm the contribution of inflammation to the pathogenesis of CHF in the general population.

Inflammatory Markers and Depressed Mood in Older Persons: Results from the Health, Aging and Body Composition Study

Patients with major depression have elevated levels of inflammatory cytokines. We examined the link between inflammatory markers and depressed mood in a community-based sample of older people. Data are from 3024 well-functioning older persons, 70-79 years of age, participating in the Health, Aging and Body Composition study. Depressed mood was defined as a Center for Epidemiologic Studies Depression scale score of 16 or higher. Plasma concentrations of interleukin (IL)-6, tumor necrosis factor (TNF)-alpha, and C-reactive protein (CRP) were measured. Compared with the 2879 nondepressed subjects, the 145 persons with depressed mood had higher median plasma levels of IL-6 (2.04 vs. 1.83 pg/mL, p =.02), TNF-alpha (3.43 vs. 3.16 pg/mL, p =.05), and CRP (1.96 vs. 1.66 mg/L, p =.03). After adjustment for health and demographic variables, depressed mood was especially prevalent among persons who had a high (above median) plasma level for at least two of the inflammatory markers. Compared with those without high levels, for persons with a high level for two or all three markers the risk of depressed mood was 2.45 (95% confidence interval [CI] = 1.34-4.47) and 2.40 (95% CI = 1.27-4.53), respectively. The association between depressed mood and serum level of IL-6 was significantly stronger in men than in women. In old age, depressed mood is associated with high levels of inflammatory markers, suggesting that depressed mood is causing and/or caused by systemic inflammation.

Change in muscle strength explains accelerated decline of physical function in older women with high interleukin-6 serum levels

OBJECTIVES: To test whether accelerated sarcopenia in older persons with high interleukin (IL)‐6 serum levels plays a role in the prospective association between inflammation and disability found in many studies.

Interleukin-6 and risk of cognitive decline: Macarthur studies of successful aging

ObjectiveTo investigate whether plasma interleukin-6 (IL-6) is cross-sectionally related to poorer cognitive function and whether a baseline plasma IL-6 measurement can predict risk for decline in cognitive function in longitudinal follow-up of a population-based sample of nondisabled elderly people. MethodsA prospective cohort study of 779 high-functioning men and women aged 70 to 79 from the MacArthur Study of Successful Aging was conducted. Regression modeling was used to investigate whether baseline IL-6 levels (classified by tertiles) were associated with initial cognitive function and whether IL-6 levels predicted subsequent declines in cognitive function from 1988 to 1991 (2.5-year follow-up) and from 1988 to 1995 (7-year follow-up). ResultsSubjects in the highest tertile for plasma IL-6 were marginally more likely to exhibit poorer baseline cognitive function (i.e., scores below the median), independent of demographic status, social status, health and health behaviors, and other physiologic variables (odds ratio [OR] = 1.46; 95% CI: 0.97, 2.20). At 2.5 years, those in both the second tertile of IL-6 (OR = 2.21; 95% CI: 1.44, 3.42) and the third tertile (OR = 2.03; 95% CI: 1.30, 3.19) were at increased risk of cognitive decline even after adjusting for all confounders. At 7 years of follow-up, only those in the highest IL-6 tertile were significantly more likely to exhibit declines in cognition (OR = 1.90; 95% CI: 1.14, 3.18) after adjustment for all confounders. ConclusionsThe results suggest a relationship between elevated baseline plasma IL-6 and risk for subsequent decline in cognitive function. These findings are consistent with the hypothesized relationship between brain inflammation, as measured here by elevated plasma IL-6, and neuropathologic disorders.

Cardiovascular Disease, Interleukin-6, and Risk of Mortality in Older Women The Women’s Health and Aging Study

Background —Systemic chronic inflammation has been found to be related to all-cause mortality risk in older persons. We investigated whether specific chronic conditions, particularly cardiovascular disease (CVD), affect the association between high interleukin (IL)-6 level and mortality in a sample of disabled older women. Methods and Results —IL-6 serum level was measured at baseline in 620 women ≥65 years old. The presence and severity of medical conditions was ascertained by standard criteria that used multiple sources of information. The sample was surveyed over the 3-year follow-up. After adjustment for potential confounders, compared with those in the lowest tertile, women in the highest IL-6 tertile were at higher risk of all-cause mortality. The presence of CVD, however, strongly affected the risk of mortality associated with high IL-6. Among women with prevalent CVD, those with high IL-6 levels had >4-fold risk of death (RR 4.6; 95% CI 2.0 to 10.5) compared with women in the lowest tertile, whereas the relative risk associated with high IL-6 among those without CVD was much lower and not significant (RR 1.8; 95% CI 0.7 to 4.2). Adjustment for all chronic diseases and disease severity measures, including ankle-brachial index, forced expiratory volume, and exercise tolerance, did not change the results. Conclusions —IL-6 level is helpful in identifying a subgroup of older CVD patients with high risk of death over a period of 3 years. Systemic inflammation, as measured by IL-6, may be related to the clinical evolution of older patients with CVD.

Higher Inflammatory Marker Levels in Older Persons: Associations With 5-Year Change in Muscle Mass and Muscle Strength

BACKGROUNDnThere is growing evidence that higher levels of inflammatory markers are associated with physical decline in older persons, possibly through the catabolic effects of inflammatory markers on muscle. The aim of this study was to investigate the association between serum levels of inflammatory markers and loss of muscle mass and strength in older persons.nnnMETHODSnUsing data on 2,177 men and women in the Health, Aging, and Body Composition Study, we examined 5-year change in thigh muscle area estimated by computed tomography and grip and knee extensor strength in relation to serum levels of interleukin-6 (IL-6), C-reactive protein, tumor necrosis factor-alpha (TNF-alpha), and soluble receptors (measured in a subsample) at baseline.nnnRESULTSnHigher levels of inflammatory markers were generally associated with greater 5-year decline in thigh muscle area. Most associations, with the exception of soluble receptors, were attenuated by adjustment for 5-year change in weight. Higher TNF-alpha and interleukin-6 soluble receptor levels remained associated with greater decline in grip strength in men. Analyses in a subgroup of weight-stable persons showed that higher levels of TNF-alpha and its soluble receptors were associated with 5-year decline in thigh muscle area and that higher levels of TNF-alpha were associated with decline in grip strength.nnnCONCLUSIONSnTNF-alpha and its soluble receptors showed the most consistent associations with decline in muscle mass and strength. The results suggest a weight-associated pathway for inflammation in sarcopenia.