3.
Risk factors and pathology
First
of all, it appears we must involve growth and development at younger ages when
discussing longevity because of the major links existing between the different
periods of life concerned. To illustrate this assertion, calcium, protein
intake and physical exercises in youth are now recognized as important
determinants of the adult peak bone mass, reached before the age of 20
(28). The level of this peak is well correlated
with the risk of osteoporotic fracture in old age (29). Moreover, during youth
and early adulthood, the functional abilities and the physiological reserves
raise to their maximum, which will prime the organism for an adaptive
response, making it ready and able to react to sudden physiologic stresses
(30). Alterations in the dynamics of physiologic systems, in advanced age,
will lead to functional decline and frailty (31). Therefore, physical
exercises are important all along our life. Recent studies demonstrated that
moderate physical activity in post-menopausal women (aged between 55 and 69
y.) is associated with a reduced risk of death from cardiovascular and/or
respiratory diseases (32) and from
breast cancer (33). The
positive role of physical activities at all ages to protect against loss of
life, physical deterioration and perhaps mental decline has to be emphasized.
Other
important factors acting on life expectancy and age-related diseases are
dietary habits and nutrition (differential consequences of famine, starvation
and caloric restriction will not be discussed here). Survivors of two
successive Scottish studies of “the childhood intelligence quotient” were
included several decades later in a new study including MMSE and measures of
blood folate, vitamin B-12, and homocysteine concentrations. Results showed
that low levels of vitamins B and high levels of homocysteine are associated
with cognitive variation in old age. Homocysteine accounted for approximately
7-8 % of the variance in cognitive performance (34). Another recent Italian,
population based cross-sectional study showed - after adjustment for age, sex,
education, total energy intake, cigarette smoking, alcohol consumption and
physical activity - that a better score assessing “healthy” diet (as
defined in the WHO guidelines for the prevention of chronic diseases) is
associated with a lower prevalence of cognitive deficit (odds ratio 0.85 [95%
CI 0.77-0.93]) (35). As previously stressed, dietary habits and nutrition are
essential all along life. They not only allow to avoiding cognitive decline in
old age but they also favourably interact with risk factors of cardiovascular
pathologies. A 10-year follow-up study conducted in Argentina proved that
great dietary modifications occurred during the study-period (decrease in
fatty foods - meat, butter, milk and other diary products – and increase in
fibre rich products, oil and low fat products) producing significant positive
changes in biological data (decrease in cholesterol levels and improvement of
total-cholesterol/HDL-cholesterol ratio), particularly in the younger and
women (36). To testify the important contribution of diet on cardiovascular
risk factors a recent meta analysis of 11 randomised controlled studies showed
that the level of sodium intake was significantly and positively linked with
the systolic blood pressure, which appeared as one of the strongest risk
factor of cardio-vascular pathologies (stroke, myocardial infarction, heart
failure) in old age (37).
Risk
factors of cardiovascular diseases are less numerous in the very old and multiple
epidemiological data now emphasize that the cardiovascular relative risks
associated with arterial hypertension, namely dyslipidemia, impaired glucose
tolerance and obesity diminish with advancing age (38). However, if hypercholesterolemia
and high blood pressure per se are no more predictors of cardio-vascular pathology,
pulse pressure (the difference between systolic and diastolic blood pressure)
and murmurs in the neck are now considered as highly predictive of heart failure
in women over 80. Surprisingly, in this study, proteinuria and tachycardia
were risk factors of cardio-vascular pathology in 80+ men (39). All this could
simply indicate that elderly persons are the survivors of a population where
significant mortality has already made its marks (39). But, what is important
to underscore, is the accumulation of cardio-vascular risk factors with advancing
age. Among elderly hypertensive persons, about 39 % of coronary events in
men and 68 % in women are attributable to the presence of two or more additional
risk factors: glucose intolerance, obesity, and dyslipidemia; the latter might
be attributed to insulin resistance promoted by abdominal obesity. These facts
reinforce the need for multivariate risk assessment profiles (40).