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Total mortality after changes in leisure time physical activity in 50 year old men: 35 year follow-up of population based cohort

BMJ 2009; 338 doi: (Published 06 March 2009) Cite this as: BMJ 2009;338:b688

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Blood viscosity is the common factor in the aging process, physical activity and smoking.

The number of significant, relevant omissions in this paper raises
the important question, " What is the value of doing medical research if
the published findings are ignored by others ?" Perhaps of even greater
importance is that the journal referees also were unaware of the

Mortality was related to leisure time activities in an aging cohort
followed for 35 years, and the beneficial effects of physical activity
were compared with the benefits which follow the cessation of smoking.
But no where in the text is the "Why" question raised. Why did leisure
activities reduce age-related mortality ? Why were the beneficial effects
of such activities similar to those which followed stopping smoking ? The
answers to such questions have been available for a long time.

What is most surprising is that during the 35 year follow-up, none of
the 8 co-authors had by chance stumbled across any of those reports which
showed (a) that the aging process is accompanied by an increase in blood
viscosity (1); (b) that regular low intensity physical activity lowered
blood viscosity (2); (c) that cigarette smoking increased blood viscosity,
while cessation of smoking led to the normalisation of blood viscosity

Because the authors chose to ignore the published information about
the adverse effects of increased blood viscosity, participants would
remain unaware of the potential benefits, for example, of an appropriate
diet. While the authors may have achieved their objective, it is a pity
that they were unable to explain to the participants why physical activity
was important in countering the changes which occur during the aging


1. Ajmani RS, Rifkind JM. Hemorheological changes during human aging.
Gerontology 1998; 44: 111-20.

2. Ernst E. Influence of regular physical activity on blood rheology.
Eur Heart J 1987; 8 (Suppl G): 59-62.

3. Ernst E, Matrai A. Abstention from smoking normalises blood rheology.
Atherosclerosis 1987; 64: 75-7.

Competing interests:
None declared

Competing interests: No competing interests

20 April 2009
Les O. Simpson
retired experimental pathologist
Dunedin, New Zealand 9077