Final answer:
Older men and women experience changes in sexual desire and function; men often face a decline due to lower testosterone levels, whereas women may find increased enjoyment due to no longer fearing unwanted pregnancy and more recognition of their sexual dysfunctions in medical fields.
Step-by-step explanation:
In the HSRC model, both older men and women experience changes in sexual desire and function, but these changes can be inconsistent across genders. For men, the decline in function may begin from around 40 to 50 years of age due to decreases in Leydig cell activity, leading to lower testosterone levels and symptoms such as reduced libido, which is sometimes referred to as andropause. In contrast, women might experience an increase in enjoyment of sex during old age as the risk of unwanted pregnancy is removed and sexual dysfunctions are starting to be better addressed medically.