Vitamin Information Center

Attributable Risk Proportion
Synonyms
 Population Attributable Risk (PAR)
Definition
The term “attributable risk” describes the proportion of
disease that can be attributed to exposure to a risk factor
( hazard) that persons in a population have experienced.
Population attributable risk (PAR) is the risk
of a specified disease or other outcome of interest in
a defined population that can be attributed to an exposure
of interest. The PAR is the incidence rate of a condition
in a specified population that is associated with
or attributable to exposure to a specific risk factor (hazard).
The PAR in a total population is the proportion of the
incidence or risk of a disease that can be attributed to
exposure to a specific risk factor; this means the difference
between the risk in the total population and the
risk in the unexposed group.
The PAR in occupational health is the percentage of
a given illness or outcome that could be prevented if
the occupational factor causing or contributing to the
illness or outcome was eliminated.

Aging and Health
MICHAL ENGELMAN
Department of Population and Family Health Sciences,
Johns Hopkins University, Bloomberg School
of Public Health, Baltimore, MD, USA
mengelma@jhsph.edu
Synonyms
Elderly and health; Health of the elderly; Older people
and health
Definitions
Population aging, the demographic process by which
older persons become a proportionally larger share of
the total population, is associated with changing patterns
of mortality, morbidity, and disability (UNPD
2002). In the older population different aspects of
health have to be considered.  Gerontology, the scientific
study of the biological, psychological, and sociological
phenomena associated with old age and aging,
and geriatrics, the branch of medicine that focuses on
health promotion and the prevention and treatment of
disease and  disability in later life, both deal with the
well-being of older people.
Basic Characteristics
A gradual  demographic transition – from patterns of
high fertility and high mortality to patterns of lower fertility
and later mortality – has been underway across
the globe. Lower birth rates and growing longevity have
led to an overall increase in both the absolute number
and relative proportion of older people in the general
population. By 2002, the population of individuals 60
years and over reached 626 million, or 10 percent of
the total world population. Of these, nearly 70 million
are among the oldest-old, aged 80 or over. The older
population is projected to expand rapidly in the coming
decades, more than tripling its current size and reaching
2 billion by 2050. The oldest-old population is expected
to grow more than 5.5 times to reach 379 million by
2050. Decreasing fertility rates contribute to the prediction
that older individuals will at that time constitute 21
percent of the total world population, twice their current
proportion and equal to the number of predicted children.
The proportion of the oldest-old will quadruple
to 4 percent by the same year (UNPD 2003). Women
constitute the majority of older people in most countries
(Velkoff, Lawson 1998).
The demographic changes are linked with  epidemiologic
transitions, in particular a shift in the leading
causes of death away from infectious, acute diseases
in early life towards chronic and degenerative illnesses in mid- and later life. Given the increase in total
 life expectancy, a number of gerontological theories
addressing the implications of increased longevity for
population health have emerged, each proposing different
relationships between old-age mortality, morbidity,
and disability, or limitations in performing activities of
daily living. (For a review, see Agree, Freedman 1999)
The theories range from the most pessimistic – in which
delayed mortality is translated to increased years of life
with disease and disability – to the most optimistic, in
which morbidity and disability are compressed towards
the end of life, increasing the healthy proportion of
total life expectancy. More nuanced perspectives recognize
the complexity, mutability, and inter-connectedness
of the processes determining morbidity, disability,
and mortality, and suggests a continuous dynamic
relationship between them. International trends in mortality
and disability outcomes are mixed, supporting
a dynamic model of longevity and health in later life
that is influenced by a multitude of biomedical, environmental,
and social factors.
Population aging is an aggregate mark of human success
in reducing fertility, improving living conditions,
and curbing risks of death through innovations in public
health and medicine. However, insufficient preparedness
for the needs of an aging population on the part of
health and social service providers is a challenge confronting
societies at all levels of development.
Geriatric Health
Aging populations have higher rates of chronic disease
and  disability, and the likelihood of having multiple
co-morbidities rises significantly with age. In high
and low-income countries alike, ischemic heart disease
and cerebrovascular diseases are the leading causes of
death. In more developed nations, cancers (lung, colon,
rectum, stomach, and breast), chronic obstructive pulmonary
diseases, diabetes mellitus, and Alzheimer’s
Disease and other dementias are also among the most
prevalent causes of death. A range of chronic and
adult-onset conditions including depression, hearing
loss, alcohol-use disorders, osteoarthritis, schizophrenia,
bipolar disorders, and chronic obstructive pulmonary
diseases are among the leading causes of global
disability (Murray et al. 2001). Chronic diseases may
contribute to the gradual loss of senses such as sight
and hearing, to impaired mobility, to increased risks of
falls and fractures, and to disability in the performance
of activities of daily living.
As  senescence, or the slowing-down of physical systems
that takes place as the body ages, progresses,
a range of physical and mental capacities is weakened.
Age-related mental illness, especially dementia,
are particularly difficult to cope with for both patients
and caregivers alike. Dementia is a condition of irreversible
decline in cognition, functioning and behavior.
Alzheimer’s disease (AD) accounts for approximately
60–70% of dementia cases, with vascular dementia
accounting for the majority of the rest. The prevalence
of AD is estimated to be 8–15% in persons over 65. The
primary risk factor for dementia is age, with the prevalence
doubling for every 5-year age group after the age
of 65 and reaching as high as 39 percent after age 90
(Jorm, Jolley 1998).
Chronic diseases exact a heavy burden on older adults
due to associated long-term illness, diminished quality
of life, and increased health care costs. Although
the risk of disease and disability clearly increases with
advancing age, poor health is not an inevitable consequence
of aging. A healthy lifestyle (including regular
physical activity, a nutritious diet, and avoidance
of tobacco) is the recommended course for prevention.
Screening for early detection is also recommended for
those illnesses (e. g. some cancers, diabetes and its complications,
etc.) for which a course of treatment is available.
Aging and Pharmacotherapy
Older people are particularly susceptible to the risks of
medication use. Age-related loss of physiologic reserve
leads to pharmacokinetic changes and increases interindividual
variability. The loss of renal function, for
example, decreases the clearance of common drugs in
older people, while the loss of lean body mass and fat
mass leads to an altered volume of drug distribution.
Polypharmacy – the use of multiple (usually 5 or more)
medications – is a common issue since geriatric patients
frequently have multiple co-morbidities each treated
with one or more medication. Furthermore, some medications
bring about  side effects that then lead to
the prescription of additional drugs to treat the added
symptoms. Polypharmacy increases the potential of
drug interactions, adverse drug reactions, and the use
of inappropriate medications, or drugs that should be avoided in certain doses, disease states, or in combination
with other drugs (Hanlon et al. 2001).
Care-Giving
Historically, older people in need of assistance received
care from younger family members. However, previously
high levels of mortality and fertility meant that
the proportion of individuals reaching older ages was
relatively small while a larger pool of children and relatives
was available to share care-giving responsibilities.
More recently, the proportion of the population
at older ages has been expanding as the numbers of
younger family members available to provide care has
been shrinking.
Women – wives, daughters, daughters-in-law, nieces
and granddaughters – have traditionally provided the
bulk of family care-giving and continue to do so despite
rising levels of labor force participation. Older people
are as likely to provide care as they are to receive it,
and in developing and developed countries alike, spouses
are the main caregivers for both men and women.
Because of the sex differential in longevity, however,
women are more likely than men to find themselves
without a spouse and to be living alone when they need
care (Velkoff, Lawson 1998).
A relatively small proportion of older people – between
1 and 10 percent – reside in institutions in developed
nations (Velkoff, Lawson 1998). There has been growing
concern – though not much documentation – that as
networks of family caregivers shrink the rate of institutionalization
among older people may rise. Additional
concerns about the quality and cost of institutional care
are garnering attention in many countries.
Aging in Developing Nations
In developing nations a rapid  demographic transition
has outpaced economic development. Since 1980,
developing countries have been home to a larger proportion
of the world’s population of persons aged 60
and above than their industrialized counterparts (Lloyd-
Sherlock 2000). By 2000, 249 million people, or 59%
of the world’s 65 years of age and over population lived
in developing countries (US Census Bureau 2001).
According to demographic projections, by 2050, more
than three-quarters of the world’s older people will
be living in developing countries. By 2050 developing
countries will posses a similar age structure to
today’s more industrialized nations. Older people will
then comprise over 30% of the population in East Asia,
more than 20% of the population in Southern Asia and
Latin America, and approximately 10% of the population
in Africa (UNPD2003).
Though they are among the most disadvantaged populations
in developing nations, older people have not
been prioritized by international aid agencies. Eighty
percent of older people in developing countries have no
regular incomes, and approximately 100 million older
persons live on less than a dollar a day. Older people
in developing regions are often excluded from economic
development, healthcare and education programs
due to age limits and discrimination and humanitarian
agencies often fail to identify older people as a target
in the planning and delivery of services in conflict
areas (Help – Age International 2002). While incidence
of chronic and age-related disease has been rising
rapidly in developing nations, there is a lack of professionals
in geriatric medicine, preventing older adults
from receiving the health care they need (Keller et al.
2002).
Though norms of filial piety are still strong in many
developing countries, changes in family structures and
co-residence patterns are rendering traditional support
networks more vulnerable. Recognizing the need for
increased awareness and action on issues related to
global aging, the Second World Assembly on Aging
adopted the Madrid International Plan of Action in
2002. The Plan calls on governments, non-governmental
organizations, and the international community to
adopt the concept of “a society for all ages,” to end
age-based discrimination and abuse, and incorporate
the concerns of older people into national and international
economic and social development policies (United
Nations Programme on Ageing, 2002). The formation
of implementation andmonitoring strategies for the
Plan is now in progress.
Cross-References
 Age-Dependency Ratio
 Demographic Transition
 Disability
 Epidemiologic Transition
 Geriatrics
 Gerontology
 Life Expectancy
 Population Aging
 Senescence
References
Agree EM, Freedman VA (1999) Implications of Population
Aging for Geriatric Health. In: Gallo JJ (ed) Clinical Aspects
of Aging, 5th edn. Williams and Wilkins Inc., Baltimore,
MD, pp 659–669
Hanlon JT, Schmader KE, Ruby CM, Weinberger M (2001) Suboptimal
prescribing in older inpatients and outpatients. JAGS
49:200–209
HelpAge International (2002) State of the World’s Older People
2002. HelpAge International, London
Jorm AF, Jolley D (1998) The incidence of dementia: a metaanalysis.
Neurology 51:728–733
Keller I,Makipaa A, Kalenscher T, Kalache A (2002) Global Survey
on Geriatrics in the Medical Curriculum. World Health
Organization, Geneva
Lloyd-Sherlock P (2000) Old age and poverty in developing
countries: New policy challenges. World Development
28(12):2157–2168
Murray CJ, Lopez AD, Mathers CD, Stein C (2001) The Global
Burden of Disease 2000 Project: Aims, Methods and Data
Sources. World Health Organization, Geneva
United Nations Population Division (UNPD), Department of
Economic and Social Affairs (DESA) (2002) World Population
Ageing: 1950–2050. United Nations, New York
United Nations Population Division (UNPD), Department of
Economic and Social Affairs (DESA) (2003) World Population
Prospects: The 2002 Revision. United Nations, New
York
UN Programme on Ageing, Division for Social Policy and Development
(2002) Madrid International Plan of Action on Ageing.
United Nations, New York
U.S. Census Bureau (2001) Series P95/01–1, An Aging World:
2001. US Government Printing Office, Washington DC
Velkoff VA, Lawson VA (1998) Gender and Aging: Caregiving.
International Programs Center. U.S. Census Bureau, Washington
DC

Adolescent Health and Development
ADALINE ZENOBIA MUYEED
Senior Technical Officer, Strategic Information,
Family Health International, Arlington, VA, USA
amuyeed@jhsph.edu
Definition
Adolescence is defined as the period between childhood
and adulthood when multiple developmental processes
occur. These areas of development include physical
growth, pubertal maturation, cognitive transitions, and
psychosocial and social maturation. Early, middle, and
late adolescence are defined in pediatrics by sub-categories
of chronological age: early adolescence is characterized
as ages 11–14; middle adolescence, ages 15–17; and late adolescence as 18–21 years of age. However,
young people between the ages of 10 and 24 years
are considered, especially in light of the fact that the age
at which young people assume adult roles is increasing
globally. Although chronological age is an important
indicator of adolescent development and provides
an objective and practical measure, it does not account
for individuals on different developmental trajectories
in terms of physical, cognitive, and psychosocial maturation.
The notion of “adolescence”, defined as an exploratory
period between childhood and adulthood when young
people typically have few responsibilities, has been said
to be relevant mainly to advanced economies; young
people (both men and women) in other parts of the
world move directly from childhood to taking on adult
roles. However, as compared with 20 years ago, there
is evidence that a large number of young people (the
total population of 10–24 year olds is estimated to have
reached 1.5 billion worldwide by 2005) are now entering
adolescence earlier and healthier, are more likely to
stay in school longer, to postpone entry into the labor
force, and to delay marriage and childbearing (National
Research Council and Institute of Medicine 2005).
A focus on adolescence is therefore gaining more attention
worldwide. The need to help young people transition
to successful adult roles such as work, citizenship,
marriage, and parenthood is being advocated.
Basic Characteristics
Adolescent Development
Physical Growth and Maturation Adolescents experience
rapid acceleration in physical growth (increase
in height and weight;  physical maturation), and
pubertal and sexual maturation ( pubertal maturation),
including further development of reproductive
organs and development of secondary sexual characteristics
(such as breast development in girls, genital
development in boys, and pubic hair in both). Age at
 menarche is the most commonly reported indicator
of sexual maturity in girls. Other physical manifestations
include changes in body composition, and
the quantity and distribution of fat and muscle. There
are also changes in circulatory and respiratory systems
which lead to increased strength and tolerance for exercise.
The growth spurt occurs about 2 years earlier in
girls compared with boys. These physiological changes occur between the ages of 9 and 16; however, there is
inter-individual variation in the timing and tempo of
these events (Steinberg 1993).
Cognitive Transitions From early adolescence
onwards, adolescent thinking is characterized by increased
knowledge, multi-dimensional thinking, and
the ability for hypothetical reasoning ( cognitive
development). Piaget described a shift from concrete to
abstract thinking (such as the ability to see various sides
of an issue and the perspective of others). The ability to
think abstractly is made possible by cognitive advances
that emerge between the ages of 11 and 20 years (Keating
1990). A liability of this developmental shift can be
an overestimation of abilities.
Psychological and Social Transitions Adolescents
grapple with issues of identity development, achievement,
autonomy, intimacy, and sexuality during the
adolescent period ( psychosocial development). The
process of identity formation can take various paths
(with a variable degree of exploration, seeking of alternatives,
and sense of commitment), and some of these
tend to be more adaptive than others. There are multiple
domains of self-evaluation and self-description including
scholastic and athletic achievement, and physical
appearance, etc. The process of individuation, and
increasing autonomy during this period, although culturally
variable, can be the basis of potential conflict
with authority figures, including parents. There is a line
of research studying the effectiveness of different types
of parenting style on teens, including democratic, autocratic
and permissive styles, which allow a different
degree of autonomy and negotiation. The choice and
effectiveness of the various styles may be based on cultural
preferences and social context.
Adolescence is a time of life when people expand their
circle of significant others to include peers and other
adults ( social transition). Young people also begin
to navigate through social institutions such as school.
Parents, guardians, teachers, classmates, and friends are
important socializers. Social acceptance and integration
become salient, and we see the development of friendships;
in particular with larger  peer groups and/or
more intimate relations, such as in close friendships.
There is a shift from same sex to opposite sex interest,
and young people may begin dating, experience romantic
relationships and become sexually active. Adolescent Health
Good physical and mental health, as well as the knowledge
and means to sustain good habits, are key for
healthy development in adolescents as many health
compromising behaviors emerge during this period. It
is known that the major causes of mortality and morbidity
in youth are behavior related, and therefore can
be prevented. In the United States, for example, youths
between the ages of 15 and 25 are more likely to suffer
from unintentional injuries (such as motor vehicle
accidents, drowning and sports/recreational-related
incidents), homicide, violent crimes, and suicide. Other
health related problems that are prevalent in youth
include alcohol use, tobacco use, illicit drug use, obesity/
weight problems, eating disorders, teenage pregnancy
and childbearing, and sexually transmitted infections,
including HIV. There are regional variations in
causes of death; for example, HIV/AIDS is the main
cause of death in youth in Sub-Saharan Africa, whereas
deaths from non-communicable diseases are more
prevalent in other regions, as discussed earlier (National
Research Council and Institute of Medicine 2005).
Pregnancy and childbirth-related mortality and morbidity
due to early childbirth (in Sub-Saharan Africa and
South Asia) and abortion (in all developing regions)
are substantial. Health compromising behaviors have
a grave impact on individuals, societies and economies
in the long-run
Mental health illnesses pose a major burden of disability
worldwide. In the US, mental and addictive disorders
(including anxiety disorders, disruptive disorders,
mood disorders, and substance use disorders) are
prevalent in one out of five 9–17 year olds (USDHHS
1999). Mood disorders such as depression, for example,
are known to be associated with academic, social, and
behavioral problems (including suicide) during adolescence.
Risk factors such as poverty, violence, and trauma,
among others, contribute to mental illness in youth
worldwide. There is a need to address the stigma associated
with adolescent mental health. Global policies
that will integrate mental health policy into the overall
healthcare system and assess the global treatment
gap are programmatic challenges are being advocated
by the World Health Organization (WHO) (WHO
2005). It is important to promote preventive interventions,
as they have been shown to cause sustained reduction
of depression and feelings of hopelessness, but also
aggressive and delinquent behavior, and alcohol, tobacco
and drug use (WHO 2003).
Health Interventions
Steps can be taken to help young people navigate successfully
through themultiple transitions and influences
of adolescence, and remain healthy. Different approaches
have been undertaken to understand and enable positive
health and development in youth. These include
developmental, ecological, and life cycle approaches,
among others. Contemporary developmental theory and
research stresses the dynamics of individual-context
relations in understanding behavior and developmental
change. Ecological approaches address the individuallevel
(such as timing of puberty, temperament, and
age), micro-level (the immediate relationships such as
parents, peer, and teachers), environmental (the home,
school, and neighborhood), and broader macro-level
influences and forces (such as cultural factors, poverty,
political instability, and the media) that influence adolescent
health and development for successful intervention.
The life cycle approach requires the understanding
that promoting and sustaining the health and development
of youth begins in childhood, and continues
throughout the life of individuals. It is useful to end
with the WHO conceptual framework, which presents
a wide array of enabling factors that begin early in life
to promote healthy adolescent development. These factors include promotion of healthy behaviors, life-long
learning and education during adolescence, preceded
by good nutrition, a safe environment, and healthy
development, beginning in childhood (TheWorld Bank
Group 2006).
Cross-References
 Cognitive Development
 Menarche
 Peer Group
 Physical Maturation
 Psychosocial Development
References
Keating D (1990) Adolescent Thinking. In: Feldman S, Elliott G
(eds) At the Threshold: The Developing Adolescent. Harvard
University Press, Cambridge, MA, pp 54–89
National Research Council and Institute of Medicine (2005)
Growing Up Global: The Changing Transitions to Adulthood
in Developing Countries. Panel on Transitions to Adulthood
in Developing Countries. Lloyd CB (ed) Committee on Population
and Board on Children, Youth, and Families. Division
of Behavioral and Social Sciences and Education. The
National Academic Press, Washington, DC
Steinberg L (1993) Biological Transitions. In: Steinberg L (ed)
Adolescence, 3rd edn. McGraw-Hill, New York, pp 22–55
US Department of Health and Human Services (USDHHS)
(1999) Mental Health: A Report of the Surgeon General,
Substance Abuse and Mental Health Services Administration,
Center for Mental Health Services, National Institutes
of Health, National Institutes of Mental Health
The World Bank Group (2006) Children and Youth Web-site.
http://web.worldbank.org/WBSITE/EXTERNAL/TOPICS/
EXTCY/0,,menuPK:396453~pagePK:149018~piPK:
149093~theSitePK:396445,00.html
World Health Organization (WHO) (2003) Investing in Mental
Health. Department of Mental Health and Substance Dependence,
Noncommunicable Diseases and Mental Health,
World Health Organization, Geneva, p 28
World Health Organization (WHO) (2005) Child and Adolescent
Mental Health Initiatives of the Department of Mental Health
and Substance Use. WHO Press, Switzerland

Having too little vitamin D in the body might raise the risk of premature death, a study by Johns Hopkins researchers shows.

It follows other recent studies showing that low amounts of vitamin D are linked to certain cancers, diabetes, and bone and immune system problems, but this is the first research to connect vitamin D deficiency to a higher risk of death, said the study’s co- author Erin Michos, an assistant professor of cardiology at Johns Hopkins School of Medicine in Baltimore.

The study appears in this week’s Archives of Internal Medicine.

Michos and her colleagues analyzed data from a large government observational survey of more than 13,000 people who represented a realistic, diverse swath of U.S. adults ages 20 or older. Participants’ vitamin D amounts were determined through blood tests from 1988 through 1994.

By 2000, Michos said, 1,807 deaths had occurred, including 777 from cardiovascular disease.

The researchers divided the total population into four groups based on their amounts of vitamin D. One group included people with the least vitamin D, 17.8 ng/mL (nanograms/milliliter) or less.

A normal vitamin D test result for both children and adults is 30 ng/mL or more. Less than 20 ng/mL is considered deficient, and results between 20 and 30 ng/mL are labeled insufficient, said Catherine Gordon, director of the bone health program at Children’s Hospital Boston.

In the study, Michos said, people who had low vitamin D — 17.8 ng/mL or less — were 26 percent more likely to be dead at the end of the study than those with more.

Michos now suspects that low vitamin D is related to heart disease deaths, but that theory has to be tested in further studies, she said.

Originally published by USA TODAY.

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Source: Tulsa World