Sunday, October 10, 2010

Reduced Disability among aging runners

Steve Runner at Phedippidations covered a great article in Episode 245 of his podcast. I could have sworn that I blogged about this in the past, but I guess I forgot at some point, so let me remedy that with this recap.

Researchers at Stanford designed a study to assess the notion that older runners would experience more disability than older non-runners due to orthopedic injuries, etc. They found a few hundred runners and non-runners and tried to match them for baseline characteristics such as age, gender, medical history, etc. Then they followed them for an astonishing 21 years! Each year asking them about injuries and disability. Many subjects died during the follow-up period, but the important findings are:
  1. Both runners and nonrunners died, but fewer runners (15% vs. 34%) died during 21 years of follow-up
  2. Runners had less cardiovascular death, but also less cancer death and dementia
  3. Runners had less average disability than nonrunners and the gap widened as subjects got into their 80's
  4. On average, runners experienced the onset of disability several years after nonrunners!
The authors admit that studies like this are subject to "self-selection" bias, which means that being a runner was not a randomized variable. This means that people who are runners might be more likely to engage in other healthy activities that the authors could not account for (wearing a seatbelt, eating fruits and vegetables, etc.) While bias MAY affect the results, this data fits with existing literature suggesting morbidity and mortality benefits of regular exercise. 

The authors summarize their findings by describing this phenomenon as the "compression of morbidity", ie: everyone dies eventually, but runners spend a shorter period of their life disabled and unable to care for themselves.

1. Arch Intern Med. 2008 Aug 11;168(15):1638-46.

Reduced disability and mortality among aging runners: a 21-year longitudinal

Chakravarty EF, Hubert HB, Lingala VB, Fries JF.

Division of Immunology and Rheumatology, Stanford University School of Medicine,
Stanford, California, USA.

BACKGROUND: Exercise has been shown to improve many health outcomes and
well-being of people of all ages. Long-term studies in older adults are needed to
confirm disability and survival benefits of exercise. METHODS: Annual
self-administered questionnaires were sent to 538 members of a nationwide running
club and 423 healthy controls from northern California who were 50 years and
older beginning in 1984. Data included running and exercise frequency, body mass
index, and disability assessed by the Health Assessment Questionnaire Disability
Index (HAQ-DI; scored from 0 [no difficulty] to 3 [unable to perform]) through
2005. A total of 284 runners and 156 controls completed the 21-year follow-up.
Causes of death through 2003 were ascertained using the National Death Index.
Multivariate regression techniques compared groups on disability and mortality.
RESULTS: At baseline, runners were younger, leaner, and less likely to smoke
compared with controls. The mean (SD) HAQ-DI score was higher for controls than
for runners at all time points and increased with age in both groups, but to a
lesser degree in runners (0.17 [0.34]) than in controls (0.36 [0.55]) (P < .001).
Multivariate analyses showed that runners had a significantly lower risk of an
HAQ-DI score of 0.5 (hazard ratio, 0.62; 95% confidence interval, 0.46-0.84). At
19 years, 15% of runners had died compared with 34% of controls. After adjustment
for covariates, runners demonstrated a survival benefit (hazard ratio, 0.61; 95%
confidence interval, 0.45-0.82). Disability and survival curves continued to
diverge between groups after the 21-year follow-up as participants approached
their ninth decade of life. CONCLUSION: Vigorous exercise (running) at middle and
older ages is associated with reduced disability in later life and a notable
survival advantage.

PMID: 18695077 [PubMed - indexed for MEDLINE]

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