What happens in our bodies as we age?

Everyone is familiar with the typical, visible signs of ageing. Wrinkles, the first grey hairs, and eyesight that gradually deteriorates. But we also age internally, and the function of many organs slowly declines. The first signs of ageing in the human body can become apparent as early as the age of 20.

Our hair turns grey because melanin production declines and eventually ceases altogether [Fernandez‐Flores et al. 2019]. Wrinkles become visible because the skin loses elasticity due to the loss of collagen, elastin and hyaluronic acid [Lapiere, 1990]. The number of hair cells in the cochlea decreases, making it increasingly difficult to hear high-pitched sounds [Huang & Tang, 2010]. As we age, the lens of the eye thickens and loses its flexibility, which limits the eye’s accommodative ability (presbyopia) and causes reading to become more difficult [Glasser & Campbell, 1999; Rich & Reilly, 2022].

From the age of 30, the elasticity of cartilage gradually decreases, making certain movements more difficult and causing our joints to become stiffer [Hudelmaier et al., 2001; Mirahmadi et al., 2017]. From this point onwards, the intervertebral discs also become thinner. Our bones begin to resorb faster than they are rebuilt, causing bone density to gradually decrease and make our bones more prone to breaking [Chan & Duque, 2002].

The brain gradually loses mass from the age of 40–50 [Hedman et al., 2011]. This impairs the transmission of signals and leads to a gradual decline in cognitive abilities [Mattson & Arumugam, 2018].

Our stamina declines because the number of alveoli decreases, leading to a reduced lung capacity and less oxygen in the blood [Astrand et al.,1973; Suki et al. 2022]. From around the age of 40, muscle mass decreases, and the body’s muscle-to-fat ratio shifts towards fat t [Evans & Campbell, 1993; Bektas et al. 2018]. The ageing process is also evident through the calcification of the blood vessels, causing the blood pressure to rise. Due to the decline in heart muscle cells and the increase in connective tissue, the performance of the heart decreases [Ribeiro et al., 2023]. Organs such as the kidneys and the liver begin to function less efficiently, meaning that the body’s detoxification process becomes slower [Wynne et al., 1989; Denic et al., 2015].

Our bladder loses elasticity and can no longer hold as high a volume of urine. The urge to urinate increases, and urination becomes less efficient, leaving a larger residual volume in the bladder[Madersbacher et al., 1998]. From the late 20s onwards, fertility in women begins to decline, accelerating after the age of 35 [Rothman et al., 2013]. In men, testosterone levels begin to decline gradually around the age of 40, and sperm motility decreases [Harman et al., 2001; Kidd et al., 2001].

The production of specific immune cells decreases, and the immune system is no longer able to fight off infections as quickly or efficientn [Goyani et al. 2024].

As the function of our organs declines with age, neurodegenerative diseases such as dementia (e.g. Alzheimer’s), Parkinson’s, cardiovascular diseases, and cancer become more common, just to name a few of the most prevalent age-related conditions [Bektas et al. 2018, Lakatta et al. 2003, Partridge et al. 2018].