The
Challenge of Longevity
Written on March 12th 2014
Life expectation at birth in Ireland
in males and females was approximately the same at about 50 years at the end of
the 19th century. Early in the 20th century life
expectation began to increase and continued gradually during the next 106 years
when the census that year confirmed mortality among males of 76.8 years and
81.6 years in females. This increase could be attributed on the one hand to a
big fall in infant mortality and to the successful control of most of the
epidemic diseases in the 1920s and 1930s. My colleagues and I in our paper
published by the American Journal of Public Health in 1970 studied the smoking
habits and mortality data in 15 different countries and we were able to
conclude that the recent mortality disparity between men and women could be
largely if not entirely attributed to cigarette smoking among men after the
last war.
The cigarette habit had increased
dramatically among men after the war thanks to the influence of the Americans
and British who were generous in supplying cigarettes to the troops and
subsequently to widespread advertising by the industry. However, it is now clear from
recent data that the disparity is now falling again and it should eventually
fall to a more equal level as cigarette smoking is falling rapidly among middle
aged men. Also it is clear that the current cigarette is less lethal because of
the use of the filter and the reduction in nicotine, tar and carbon monoxide.
It is anticipated that the results
of the last census in 2010 in Ireland will show a further improvement in life
expectation and a further narrowing in the disparity between men and women. In
an attempt to understand the continued improvement in life expectation of both
sexes, it seems worth listing the lifestyle and environmental factors which may
account for the continued upward survival trend. I am speculating in this essay on the possible opportunities
of maintaining the continued rise in life expectation above the current 2006
figures by studying the life style and other factors which may be relevant to
changes in human survival.
Infant mortality continues to be an
important factor, having fallen from 78 per thousand after the war to a
remarkable figure of 3 in 2009 and 4 in 2010 in Ireland. The figure of 3 was
the lowest ever recorded in these islands. Infant mortality has obviously
reached an optimum level of control.
The following list includes,
firstly, the factors which are likely to contribute to the continued
improvement in life expectation and, secondly, the factors which I believe are
responsible for our failure to reach our optimum age. For the sake of studying
the optimum age of humans I have suggested 95 years when 50% of the population
will have died whatever the mode of death recorded on the death certificate.
We need to look at the human gene
and its influence on longevity, How fixed is it in terms of years of survival
and in its distribution around a nominal figure of, say, 95 years? And what are
the prospects of increasing the survival capacity of the human gene through
research? And, indeed, would it be wise if we were to extend human life through
genetic manipulation? I think on this issue that I would be a vigorous
opponent.
It is necessary to identify all
known risk factors affecting health and survival and to give each an estimated
figure of the effect it may have in shortening or prolonging life within the
population. Striking a single figure might represent the mean or average of
each risk factor in terms of quantity or quality. It would obviously be an
empirical estimate and subject to major error but the potential errors inherent
in such an approach might tend to even out when all factors are taken into
account in estimating a composite influence on survival. My opinions are based
on my reading, my experience as a physician, my international role as a medical
epidemiologist and my social contacts over the last 70 or more years.
The following factors are proposed
as affecting survival with the estimated influence they may have in figures of
years:
Education, Those with a 3rd
level education in the UK have a greater survival rate than those with a first
education. I assume the same applies to Ireland. Benefit - 3 years.
Good housing, less air pollution, and
better heating, water supply, hygiene, dental care. Benefit - 0.5 years or less
survival for each factor. Obviously these are intimately related to each other
and to other factors such as education, wealth and possibly medical care.
Nutrition. Meat from domestic sources including
beef, lamb, pork and high saturated fat foods shorten life. It is likely that
the traditional Anglo-Irish emphasis on a high meat diet may be changing to
more European foods which contain less saturated fat and salt and with a
greater intake of vegetables and fruit. Vegetarians and vegans are extreme
examples of the benefits of diet. Dietary changes may account for some of the
progressive improvement in life expectation. Proposed benefit of healthy
nutrition - 4 years.
Salt. The recent substantial rise in
life expectation might be partly related to the gradual reduction in salt in
commercial foods and on the table.
There is no doubt that the very high salt intake I recall in the 1930s
and 1940s contributed to the frequency of stomach cancer (then the commonest cancer
in the population and now one of the rarest)) and hypertension and possibly to
heart disease and other chronic diseases – Risk of lifetime high salt intake -
5 years.
Alcohol – more than 21 units
weekly over the long-term. This figure includes all those who are deemed to be
alcoholics. Risk excess - 4 years.
Obesity. Weight at or above BMI
of 30. Risk - 3 years
Medical
intervention and the longer survival of the old and the
decrepit, including Ivan Illich’s concept of the living death, must contribute
to longer life expectation. Fifty or 60 years ago older people who were debilitated and
who developed an illness usually died fairly soon afterwards. Nowadays older
people can be kept alive for months or years by medical means and better
nursing, even if quality of life may be reduced. The contribution of
medical intervention (including health education) is particularly difficult to
quantify. Clearly preventive medicine in terms of health education is very
important in terms of survival, although the increasingly popular health
checks, which are widely advertised by private hospitals and clinics, are of
very doubtful value and are generally discouraged on the grounds of poor
efficacy, unnecessary medical intervention and expense.
Intervention in terms of drugs and
surgery obviously contribute to better health and survival but we have to add
iatrogenic problems and unnecessary intervention to the equation when we are
studying longevity. In aiming at better life expectancy I would give the figure
7 to medicine in general of which 4 or more I would contribute to medical
education and 3 or less to medical intervention, Medical
education and medical intervention have certainly contributed to quality of
life. Total benefit - 7 years
Aerobic exercise or a lifetime programme
starting as late as 45 or 50 years of aerobic exercise equivalent to 5 hours
walking a week or more at an optimum rate for age has been shown in many
studies to benefit longevity. Occupational and anaerobic exercise does not
provide the same benefit. Benefit of aerobic exercise – 4 years.
Family history (this figure is based on
our own work among patients with coronary disease) We found that it is the
habits shared in families which provide the risk factors for heart disease
except in the rare case where an abnormal cholesterol profile of genetic origin
is found in some or all members of a family. For example, smoking is an example
which was often a shared habit in households while other families tend to be
non-smokers. Nutrition is another
obvious shared factor. It is likely that family habits may impinge on more than
heart disease, stroke and cancer, the three biggest killers. The benefit of
family history is minimal but when heart disease was so prevalent 30-40 tears
ago it was not unexpected to find more that one case in a family. Risk not
relevant
Cigarette smoking (20 a day or more from
the age of 18 inhaling) I would posit a very substantial adverse effect of
cigarette smoking on survival from my experience, both as a physician and a
social observer, That was thirty years or more ago, when cigarette smoking was
so widespread among middle aged males and before the habit had begun to decline
and the cigarette became less lethal, Some such smokers died in the thirties
and forties and many died in the fifties and sixties. I would posit that 50% of
all men at that time who continued to smoke and inhale 20 or more cigarettes a
day would be dead between 60 and 65 years. My estimate for lifetime smokers
would be 25 years for men and 30 years for women.
The figure of 25 years may possibly
have been on the conservative side but clearly cigarette smoking is declining
rapidly to-day among middle-aged and older people and the benefits of the
decline is already apparent in the last 25 years. Cigarette smoking is not only
declining rapidly, particularly among the middle aged, but the cigarette of to-day is much
less lethal than formerly thanks to the filter and the substantial butt, to the
decline in the amount of tobacco in each cigarette and to a substantial
reduction in their nicotine and tar content. Among smokers to-day, with the
less lethal cigarette, the risk may be modified but a long term habit of
smoking with to-day’s cigarette must still involve considerable risk. Current risk 10-15years.
Other tobaccos (pipe, cigars). Their
adherents were much less vulnerable because they were seldom inhalers. Risk - 1
year. Perhaps snuff adherents had some small risk too.
Occupation - less than 1 year
Social disadvantage, including accident
proneness, poverty, chronic unemployment, criminality. Risk - 4 years
Stress. Pathological rather
than ordinary day-to-day concerns. Stress includes mental illness, accident
proneness. suicide and poverty. Risk - 3 years
Gender – No inherent risk.
It is hardly possible to quantify an
individual in terms of longevity, mainly because of earlier chance events or
illnesses but with optimum knowledge of causation and a reasonable adherence to
healthy living we should be confident of reaching the 9th or 10th
decade. However, one’s attitude to
ageing is important. It is related to the ability to adapt to the normal
physical, psychological and social changes of the third stage of life. With an
appropriate acceptance of the increasing limitations which are then inevitable,
it is possible to enjoy ageing and retirement as much as at other stages of
life, including the gradual loss of one’s friends and contemporaries. You may
become more housebound and drop more from the social scene but in this modern
world there is much to occupy oneself even if mostly confined to the home. This
aspect is dealt with in detail in my My Challenge to Ageing 3rd
edition on Kindle and is based on observing and recording my experience of and
adaptation to the 26 years of my retirement.
This estimate of allotted lifetime
reduced or increased collectively in this manner is somewhat speculative. We
obviously cannot be specific about the individual because of wide quantitative
variations in life enhancing and risk factors and variations in time of
exposure. However, if we combine the influence of two or more factors we may
arrive at a more acceptable opinion about the influence of life style on
long-term survival although we might still be without the support of firm
evidence. A few examples may suffice here;
If an obese person with a BMI of 35
who is a heavy salt eater, who tends to eat a diet rich in beef, lamb or pork
and who largely eschews vegetables and fruit, and who takes no aerobic
exercise, could have the combined estimate of risk of 15 years or more. This does
seem a lot of risk but I would think the risk is not far from reality.
If a person of reasonably normal
weight who walks or jogs at an optimum rate of 6-8 miles or more a week, who
eschews free salt and salty food, who does not smoke and who is a vegetarian
(but not necessarily vegans) will very likely reach the late 80s or the 90s, or possibility one hundred!
This combined approach to the
assessment of risk continues to lack specificity but is easier to judge as
rational if not firm on scientific grounds. It is of course, necessary to
continue studying the role of the specific risk factors which influence health
and longevity but already there is much clear evidence in the literature on
such lifestyle aspects as aerobic exercise, nutrition, smoking and salt.
In Ireland we are awaiting full
information about longevity derived from the 2010 census but the data available
so far would suggest a further increase in both males and females with a
further narrowing of the disparity between the sexes because of the dramatic
reduction in cigarette smoking in middle-aged people.