Chronic Inflammation May Preclude Healthy Aging

Ricki Lewis, PhD

September 16, 2013

Chronic inflammation is linked with a reduced likelihood of disease-free aging, according to a study published online September 16 in the Canadian Medical Association Journal. The study shows an association between elevated interleukin 6 (IL-6) levels and subsequent disease in a large group of healthy, middle-aged individuals.

Type 2 diabetes, cognitive impairment, brain atrophy, and cardiovascular disease are among the conditions associated with chronic inflammation. IL-6 is a powerful marker of systemic inflammation because it controls deployment of other cytokines and inflammatory molecules and directly affects the brain and muscles.

Tasnime N. Akbaraly, PhD, from the Institut National de la Santé et de la Recherche Médicale, and colleagues analyzed data from the Whitehall II study from the United Kingdom on 3044 adults older than 35 years (28.2% women) who had no history of cancer, stroke, or myocardial infarction at baseline in 1997-1999. The researchers measured IL-6 from blood samples taken at baseline (1997-1999) and from 1991 to 1993. They consulted hospital and register data and reports of clinical examinations to track the health of participants with follow-up from 2007 to 2009.

The researchers used 4 classifications of aging phenotypes: successful (no major chronic diseases and optimal physical, cognitive, and mental function, fatal or nonfatal cardiovascular disease, death from noncardiovascular causes, and normal aging (everyone else).

At the 10-year follow-up, 721 (23.7%) of the 3044 participants met criteria for successful aging, 321 (10.6%) had cardiovascular disease, 147 (4.8%) had died from noncardiovascular causes, and the remaining 1855 (60.9%) had the normal aging phenotype.

Individuals who had elevated IL-6 levels (>2.0 ng/L) at both times had a 47% reduced likelihood of successful aging (odds ratio [OR], 0.53; 95% confidence interval [CI], 0.38 - 0.74) compared with those who had normal IL-6 levels. In addition, those with elevated IL-6 had an increased risk for cardiovascular events (OR, 1.64; 95% CI, 1.15 - 2.33) and noncardiovascular death (OR, 2.43; 95% CI, 1.58 - 3.80).

The researchers adjusted for confounding factors, including sociodemographic data (sex, age, and economic status), health behaviors (smoking status and physical activity level), obesity, acute inflammation, and use of anti-inflammatory medications.

In addition to adding evidence to the value of IL-6 as a marker for chronic inflammation, the results suggest that "maintaining a low [IL-6] level may facilitate successful aging by reducing the likelihood of impaired respiratory and musculoskeletal functioning and increasing the likelihood of remaining free of diabetes.," the researchers write. Assessing chronic inflammation should be a standard part of geriatric practice, they add.

The investigation improves on similar efforts in considering 2 measurements of the inflammatory marker, rather than 1. Limitations of the study include generalizability beyond middle-class Londoners, failure to differentiate chronic inflammation from several acute episodes during the 5-year data collection period, and remaining confounding effects.

The authors have disclosed no relevant financial relationships.

CMAJ. Published online September 16, 2013. Full text

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