Life Expectancy and Pathogens

Life Expectancy and Pathogens

Introduction

  • The lecture focuses on life expectancy and embryonic development.

  • Importance of previous knowledge in DNA, transcription, translation, and cell biology is emphasized.

  • Reminder of upcoming test on December 1st.

Life Expectancy

  • Definition: Life expectancy refers to the average period a person is expected to live.

  • Historical context of life expectancy shows increases over time, reflecting advancements in healthcare and living conditions.

Understanding Pathogens

  • Pathogens: Infective biological agents that cause disease; examples include viruses, bacteria, and parasites.

  • Understanding their impact is essential for discussing life expectancy.

    • Mortality: Death caused by pathogens. High fatality rates seen in diseases like rabies and HIV.

    • Communicability (R0): The ability of a disease to spread from person to person.

Key Terminologies

  • R0 (Basic Reproduction Number): The average number of people that one infected person will infect.

    • R0 = 1: Average, stable infection rate.

    • R0 < 1: Disease will decline in the community (epidemic decreasing).

    • R0 > 1: Disease will increase in the community (epidemic rising).

Examples of Diseases

  • High Mortality Pathogens:

    • Rabies: Extremely high mortality rate without treatment.

    • HIV: High probability of death without treatment.

    • Tuberculosis (TB): Around a million deaths annually, particularly affecting marginalized communities.

  • Diseases with Variable Communicability:

    • Measles: Highly communicable; vaccination rates are critical.

    • Rhinoviruses (common cold) and seasonal flu: Less deadly but common.

Importance of Vaccination and Hygiene

  • Vaccination and hygiene are essential in protecting against pathogens.

    • Clean water, sanitation, and vaccination help manage infectious diseases.

    • Not all pathogens have effective vaccines (e.g., rhinovirus).

Historical Life Expectancy Trends

  • Life expectancy in 1960 was 50 years; improved to over 70 years by 2015.

    • Average Life Span: Influenced heavily by infant mortality.

    • Example Calculation:

    • 100 people total: 50 lived to 80 years, 50 died at childbirth = average life expectancy of 40 years.

    • Updated example: 95 live to 80 years, 5 die at childbirth = average life expectancy of 76 years.

Comparison of Life Expectancy: World vs. North America

  • Global Trends: Variation exists, with Sub-Saharan Africa improving from 40 to around 60 years.

  • Reasons for Improvement: Access to healthcare, food security, improved hygiene.

  • Birth Rate Correlation: As life expectancy increases, birth rates tend to decrease.

    • Societal factor: Traditionally, more children were born to offset losses from high infant mortality.

Mortality Rates and Causes of Death

  • Leading Causes:

    • Cancer and heart disease are the leading causes of death for both sexes.

    • Variations in causes of death are sex-specific (e.g., strokes for women, accidents for men).

  • Trends in North America: Mortality from infectious diseases has decreased significantly due to better healthcare.

Statistics and Changes Over Time

  • From 2000 to 2016, the incidence of deaths from cancer and heart disease decreased from 54% to 48% in Canada.

  • Changes in data collection and recording methods can impact historical and modern statistics on causes of death.

Pathogen Impact Over Time

  • Historical leading causes of death indicating a high impact of pathogens include:

    • Tuberculosis and pneumonia had significant mortality rates in the past.

    • The shift towards non-infectious diseases as life expectancy increases reflects advancements in healthcare and lifestyle.

Tuberculosis (TB)

  • TB Overview: Caused by Mycobacterium tuberculosis; historically a leading cause of death.

  • Asymptomatic Cases: 90% of infections remain asymptomatic, complicating control strategies.

  • Treatment and monitoring (e.g., X-rays) are essential in managing and understanding TB.

Effects of Life Expectancy on Genetic Selection

  • Allele Distribution and Health: Life expectancy influences which genetic traits persist in populations.

  • Example: Increase in diabetes prevalence due to longer lifespans; originally a beneficial trait in early human history (e.g., Neanderthals)

    • Mutation Effects: Changes in DNA affecting glucose metabolism may result in increased diabetes rates in longer-living populations.

Conclusion and Societal Observations

  • Accidental deaths have significantly increased, largely due to factors like drug overdoses.

  • Increased awareness and improvements in healthcare are critical to addressing these societal changes.

  • Continuing evolution of health metrics and societal norms must adapt to shifts in life expectancy and disease prevalence.

Note: The content discussed is rooted in broad biological principles and societal observations about health outcomes and their relationships to pathogens, life expectancy, and healthcare developments.