Health Psychology and Aging

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Health Psychology and Aging
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Health Psychology

• Also, behavioural medicine
• Role of behaviour in promoting health, preventing
  and treating disease
• New
• Relatively little behavioural genetics work

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Body Weight

• Genetic factors account for majority of variance
  in weight
• MZ, reared together 0.8
• MZ, reared apart 0.72
• DZ, reared together 0.43
• Biological parents offspring 0.26
• Biological parents adopted away offspring
  0.23
• Adoptive parents adopted offspring 0.01
• Heritability about 70
• Shared environment effects low

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Obesity

• Natural energy reserves (fatty tissue) exceeds
  healthy limits
• Absolute or relative terms
• Body mass index
• Weight/height2
• Exceeds 30kg/m2

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Co-morbidity

• Osteoarthritis
• Obstructive sleep apnea
• Diabetes
• Cancer
• Cardiovascular disease

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Environmental Factors

• Overeating
• High caloric, energy-dense foods
• Fast food consumption tripled and calorie intake
  quadrupled between 1977-1995 in North America
• Sedentary lifestyle

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Genetics

• Prader-Willi syndrome
• 7 gene deletion, chromosome 15q
• Bardet-Biedl syndrome
• 12 genes, chromosome 11 or 16
• BBS proteins
• MOMO syndrome
• Extremely rare (1 in 100 million births) seems
  to be autosomal dominant mutation
• Leptin receptor mutations
• Regulates adipose-tissue mass
• Melanocortin receptor mutations
• G-protein coupled receptors account for 6 of
  early-onset obesity
• Single-locus mutations only account for 7 of all
  cases of obesity

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Neurobiological Mechanisms

• Leptin
• Produced by adipose tissue
• Signals fat storage reserves in body
• Mediates long-term appetite controls (eat more
  when fat stores low, less when stores are high)
• Ghrelin
• Produced by stomach
• Modulates short-term appetite control (eat when
  empty, stop when stretched)
• Both produced peripherally, but act on CNS,
  primarily hypothalamus

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Hypothalamus

• Several circuits contribute to hypothalamus
  involvement in appetite
• Melanocortin pathway
• Arcuate nucleus (AN) --gt lateral hypothalamus
  (LH) and ventromedial hypothalamus (VMH)
• LH brains feeding centre VMH brains satiety
  centre
• When AN neurons activated --gt appetite
• Neurons inhibited by circulating leptin and
  ghrelin

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Leptin

• Leptin originally discovered 1950s homozygous
  mutation --gt obese mice
• But, not the primary cause of obesity in humans
• Over 240 other mouse genes identified in weight

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FTO

• Obesity risk allele
• 10 SNPs in first intron of FTO chromosome 16
• About 39,000 Europeans studied (Frayling et al.
  (2007))
• Versus individuals with no variant copy
• One copy, average 1.2kg heavier 30 increased
  risk of obesity
• Two copies (16 of subjects), average 3kg
  heavier, 70 increased risk of obesity
• Ethnic differences in copy variant frequencies
• 45 West/Central Europeans 52 West African 14
  Chinese and Japanese

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Addictions

• Typically, some form of chemical use
• Substance alters body physiology and/or
  neurochemistry
• Recurring compulsion
• Questions about other addictions
• E.g., food, gambling, sex
• Suggestions that these may be components of
  obsessive compulsive disorder, not addictions,
  per se

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Alcoholism

• Runs in families
• 40 and 20 risk for first degree male and female
  relatives of alcoholic proband, respectively
• 20 and 5 for general male and female
  population, respectively
• Assortative mating for alcohol use high (0.38)
• Could be inflating shared environment estimates

14
Male Twin Studies

• Moderate heritability for males, modest for
  females
• E.g., Concordances MZ 50, DZ 35
• Heritability 0.6
• Early onset and more severe alcoholism is more
  heritable

15
Female Twin Studies

• Inconsistent results
• Heritability figures range from 0.25 to 0.55

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Shared Environment

• Related to initial alcohol use in teens and young
  adults, but not to later alcohol abuse
• Effect on siblings, not parents and offspring
• Correlation for alcohol abuse in parents and
  biological teens 0.3, but only 0.04 for adopted
  teens
• Correlation for alcohol abuse in unrelated
  adopted siblings 0.24 (0.45 for same sex, 0.01
  for opposite sex)
• Sibling and/or peer effects more important than
  parent effects in adolescence

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Genotype-Environment Interaction

• Genetic risk for alcoholism greater in more
  permissive environments
• Heritability lower for
• Married individuals
• People with strong religious upbringing
• People from stricter and closer families
• Regions with lower alcohol sales

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Animal Models

• Long sleep (LS) and short sleep (SS) mice
• Inbred strain
• After 18 generations LS mice slept for average
  of 2 hours post alcohol SS mice only for about
  10 minutes
• Lot of variation in LS (1.2 - 4.4 hours) less in
  SS (0 - 0.65 hours)

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Alcohol Response Polygenic

• Suggests many genes involved
• Steady divergence over 18 generations (1 or 2
  genes would have stabilized much sooner)
• Variability in sleep times for LS and SS
• Different responses by LS SS strains to other
  drugs (e.g., cocaine, morphine)
• QTL mapping and knockout studies identify 5 genes
  for dopamine D2 receptor
• Each gene accounts for 20 minutes of sleep five
  about 130 minutes of total 170 minute difference
  between LS and SS mice

20

• Dopamine D4 receptor knockout --gt
  supersensitivity to alcohol, cocaine,
  methamphetamine
• Serotonin receptor knockout --gt increased alcohol
  consumption

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Humans

• Ethnic differences
• Mutant ALDH2 allele
• Inactivates key enzyme in alcohol metabolism
• 25 Chinese, 40 Japanese, almost no Caucasians
• But, this and other genes dont show consistent
  effects even within ethnic groups

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Smoking

• MZ concordance, 75
• DZ concordance, 63
• Heritability about 60 with some shared
  environmental effects
• Like alcohol, less parents, more peers and
  siblings

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Aging

• Tricky
• Older individuals vary greatly biologically and
  psychologically
• So, grouping into elderly for analysis not very
  effective
• Relatively little behavioural genetics work on
  second half of lifespan
• Traditional nurturist/behaviourist carry-over?

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Effects

• Specific types (e.g., Alzheimers)
• General cognitive decline
• Various tests, e.g., Informant Questionnaire on
  Cognitive Decline in the Elderly (IQCODE)
• Differences in abilities
• Fluid abilities decline (e.g., spatial)
• Crystallized abilities improve (e.g., vocabulary)
• Both equally heritable

25

• Personality traits remarkably stable across adult
  lifespan large genetic effect here
• Heritabilities of late life psychopathology and
  personality disorders very similar to younger
  rates
• Longevity only has modest genetic effects
  (heritability about 25)