L1, Demographics Flashcards
Technical definition of ageing:
Increasing chance of death with time
Life expectancy in high income vs low income world:
- High: More even distribution throughout age ranges from 0 to 75
- Low: More young individuals (pyramid)
Extrinsic mortality:
Sum of effects of external factors such as predation, starvation, etc -> factors that cause death
Exploring age demographics in prehistory:
Libben site:
- Hunter gatherer community remains found in Northern Ohio (800-1100AD)
- Very few women living past child-bearing age
- Life expectancy of 20 years
Wild chimpanzee communities:
- Shows similar distribution to Libben site
Exploring age demographics in civilised history:
- Anglo saxon remains: relatively short lives (under 45), cemetery burials
- Great socioeconomic influence; mean life span of Kings in Scotland and England: 51 and 48 respectively
Lifespan in recent history (US data):
- 1900: 47.3
- 1955: 69.6
- 2017: 78.6
Current life expectancy data (UK, 2022):
- Men: 79.3
- Women: 82.6
Potential support ratio:`
- PSR: Persons 15-64 per person 65 or older
- Worldwide: ~12:1 in 1950 vs 4:1 in 2050
Describe trends in common causes of mortality (2013 to 2022):
- Fluctuations in rate of various diseases
- Diabetes: Increase (M + F)
- AD: Major increase (M + F)
- CD: Decrease then increase (M)
- Pneumonia: General decrease (M + F)
- COVID!
- Suicides: General increase (M + F)
- Drug overdose: Rapid increase in most US age groups since ~2015
Key measures of ageing:
Generally demographic (incredibly difficult to predict on an individual level):
- Mean
- Median
- Maximum
- 90th percentile mortality time
- Rate of aging (model fitting), including MRDT (mortality rate doubling time)
- Time of onset
Gompertz parameters in model fitting:
- a: age-independent mortality rate, constant over time (usually due to extrinsic mortality in captivity)
- b: Measure of ageing; exponential increase in mortality over time (aka intrinsic mortality) -> often species specific and therefore genetic
Log mortality curves:
- Chance of death at time ‘t’
- m(t) = Ae^Gt
- Log mortality = logA + G*t
+ Explanation for differences in ageing between men and women
Women have a longer lifespan than men - this may be in part due to pre-menopausal hormonal protection. Women have a lower IMR than men but a similar MRDT; indicates the same rate of ageing - the key difference is that women have better protective mechanisms against disease. Notable hormonal contribution in each case.
- IMR = Initial mortality rate
- MRDT = Mortality rate doubling time
+ Human functional decline in comparison to mortality rates:
- Human functional decline: Appears to be linear
- Mortality rates: Exponential
- Most of functional decline seem to begin after sexual peak (~19)
+ Transthyretin Amyloidosis
- Hereditary, systemic disease cause by a mutation in Transthyretin gene on 18q12.1
- The TTR protein is synthesised primarily in the liver; carrier for thyroid hormones and RBPs -> important for tightly regulating basal metabolic rate and body temperature
- Various SNPs (80+ examples) in TTR result in misfolded, sticky amyloid proteins which tend to aggregate on interior surface of blood vessels and throughout tissues -> organ dysfunction and death (clogged pipe analogy)
- Senile systemic amyloidosis (SSA) tends to appear in older individuals (i.e. centenarians) -> amyloidosis-related causes are the primary cause of death in quasi-supercentenarian populations
