Encyclopedia of Health and Medicine

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life expectancy A statistical calculation representing
how many years a person might expect to
live. Simple life expectancy calculates projected
years of life from birth. Age-adjusted life
expectancy projects how many more years a person
of a certain age might expect to live. It is
important to remember that such calculations are
projections, not factual assertions of how long an
individual will live. Any individual may live
longer or less than his or her life expectancy as a
result of numerous variables.
Life expectancy at birth has steadily increased
in the United States, climbing by 60 percent overall
between 1900 and 2000. A child born in 1900
could expect to live about 48 years, whereas a
child born in 2000 could expect to live about 77
years. Though life expectancy for men remains
less than that for women, the gap is slowly closing.
Some health experts believe discoveries in
genetics and molecular medicine in the early years
of the 21st century have the potential to extend
life expectancy 15 to 25 percent within the next
decade.
Increases in life expectancy have historically
reflected improvements in numerous areas of
public health, ranging from sanitation to vaccinations.
Current increases reflect health and healthcare
improvements primarily in areas such as
pharmaceuticals, diagnostic procedures that allow
early detection of potentially fatal health conditions,
and therapeutic technologies. Individual
variables such as family and PERSONAL HEALTH HIS-
TORY also influence life expectancy, as do behaviors
that affect health such as cigarette smoking.
Numerous government agencies publish life
expectancy data, updated annually.
See also HEALTH RISK FACTORS; LIFESTYLE AND
HEALTH; IMMUNIZATION; YOUTH HIGH-RISK BEHAVIORS.
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lifestyle and health Many aspects of lifestyle
influence health. Among the most significant are
• cigarette smoking and other tobacco use
• diet and nutrition
• physical activity and exercise
• occupational health risks
• WEIGHT LOSS AND WEIGHT MANAGEMENT and OBESITY
• seat belt and helmet use
• SAFER SEX PRACTICES
The correlations between lifestyle behaviors
and health conditions are both direct and indirect
and often intertwined. Numerous research studies
show conclusively, for example, that cigarette
smoking is a direct cause of CARDIOVASCULAR DISEASE
(CVD), LUNG CANCER, CHRONIC OBSTRUCTIVE PULMONARY
DISEASE (COPD), laryngeal CANCER, and STOMACH CAN-
CER and a contributing cause to numerous other
cancers and diseases. Scientists and researchers
know, too, that OBESITY is a clear factor in health
conditions such as cardiovascular disease and DIA-
BETES. Furthermore, diabetes is one of the leading
causes (along with cigarette smoking and obesity)
of cardiovascular diseases such as HYPERTENSION
(high BLOOD PRESSURE), PERIPHERAL VASCULAR DISEASE
(PVD), and CORONARY ARTERY DISEASE (CAD).
Researchers also know that diet and nutrition
are key factors in healthy body function as well as
in disease states. Some diseases result directly
from nutritional deficiencies, such as pernicious
ANEMIA (vitamin B 12 deficiency, which can occur
from dietary insufficiency or due to MALABSORPTION
disorders, PEPTIC ULCER DISEASE, or GASTRECTOMY).
Researchers continue to investigate the ways in
which nutritional and dietary factors contribute
indirectly to health conditions, particularly with