The maximum life span is a characteristic of the species. It is the maximum number of years a member of that species has been known to survive. The maximum human life span is estimated to be 121 years. The life spans of tortoises and lake trout are both unknown, but are estimated to be more than 150 years. The maximum life span of a domestic dog is about 20 years, and that of a laboratory mouse is 4.5 years. However, a person cannot expect to live 121 years, and most mice in the wild do not live to celebrate their first birthday. The life expectancy, the amount of time a member of a species can expect to live, is not characteristic of species, but of populations. It is usually defined as the age at which half the population still survives.
People worldwide are living longer. This is the era, where for the first time most of people can expect to live in their sixties and beyond. Aging is an inevitable physiological change occurring in organisms over time. It ultimately ‘leads to death naturally as one gets old along with gradual dysfunctions of all organs in the organisms including unicellular organisms, plants, animals, and humans’. Aging is the direct cause of diseases and death in humans so it is one of the biggest questions among many biological phenomena.
Definitions of aging according to different people
- According to Harman , “Aging is the progressive accumulation of changes with time that are associated with or responsible for the ever-increasing susceptibility to disease and death which accompanies advancing age” and “the sum of the deleterious free radical reactions going on continuously throughout the cells and tissues constitutes the aging process or is a major contributor to it”.
- According to Hayflick , “The common denominator that underlies all modern theories of biological aging is change in molecular structure and, hence, function”.
Estimates are that the number of adults older than 65 will reach upwards of 88.5 million by 2050, which will surely place a higher demand for healthcare providers and hospital systems alike. According to WHO; between 2015 to 2050, the proportion of world’s population over 60 years will nearly be doubled from 12% to 22%. The pace of population ageing is much faster than in the past.
There are many theories and opinions about that causes ageing. Some of the few factors that are supposed to cause ageing are:
- Collagen breakdown: Collagen is a protein that is an important part of connective tissues in the body. It represents 75% of the skin’s dry weight. When this collagen are broken down or degraded, that causes ageing.
- Photo Defence: Repeated exposure to ultraviolet light (UV radiation) from the sun accounts for almost 90% of symptoms of premature skin ageing, skin damage and skin cancer. The sun is carcinogenic and harmful to the skin.
- Oxidation (oxidative stress): It turns out that oxidation, the same chemical reaction that causes iron to rust, plays a similarly corrosive role in our bodies.
- Inflammation: This is the skin’s first line of defence against foreign invaders such as bacteria and viruses. Inflammation also initiates the tissue healing process and limits the damage to skin cells caused by everyday chemicals and pollutants. Whilst it is helpful in the short term, excessive (chronic) inflammation is one of the most common themes in early-onset skin ageing. Subtle signs include skin sensitivity, redness and irritation.
- Glycation: Glycation occurs when an excess of glucose is combined with the collagen and elastin fibres. Scientific research shows that glycation is one of the main causes of skin ageing. Glycation is a chemical reaction mainly caused by the excess sugar we ingest but also oxidative stress and UV radiation.
Aging is an inevitable physiological change occurring in organisms over time. Hence, one cannot prevent aging totally but can have a healthy aging. There are some tips for healthy aging given by CDC given below:
Eat and Drink healthy: It is said that, you are what you eat. Hence, making healthy eating and drinking choices may delay aging. Foods like fruits, vegetables, whole grains, lean meats, low fat dairy products and water are good choices.
Move more, sit less throughout the day: Being active can help you prevent, delay, and manage chronic diseases; improve balance and stamina; reduce risk of falls and also improve brain health. Which ultimately delays aging.
Don’t use tobacco:
Get regular checkups
Be aware of changes in brain health
References
Park DC, Yeo SG. Aging. Korean J Audiol. 2013;17(2):39-44. doi:10.7874/kja.2013.17.2.39
Pallin DJ, Espinola JA, Camargo CA. US population aging and demand for inpatient services. J Hosp Med. 2014 Mar;9(3):193-6
https://www.helpage.org/resources/ageing-data/global-ageing-statistics/
https://www.ocosmedics.com/article/causes-of-aging
https://www.who.int/news-room/fact-sheets/detail/ageing-and-health
Liochev SI. Which Is the Most Significant Cause of Aging?. Antioxidants (Basel). 2015;4(4):793-810. Published 2015 Dec 17. doi:10.3390/antiox4040793