In the affluent Western countries, including the UK and the US, measurable life satisfaction follows a U-shape curve, dipping to a low in midlife but rising again in later life (despite physical ageing).
Life satisfaction in Africa tends to be consistently low throughout life. People living in Eastern Europe, the former Soviet Union and Latin America tend to experience declining happiness with age, with no discernible improvements in later life.
Roberts, M. (2014). Happiness ‘dips in midlife in the affluent West’. London: BBC Health News, November 6th 2014.
This relates to:
Full Text Link (Note: This article requires a suitable Athens password, a journal subscription or payment for access).
Steptoe, A. Deaton, A. [and] Stone, AA. (2014). Subjective wellbeing, health, and ageing. The Lancet. November 6th 2014. [Epub ahead of print].
A more recent investigation, of likely interest:
Kar, N. (2019). Being happy in old age: reasons, methods and challenges. Journal of Geriatric Care and Research. November 25th 2019, Vol.6(2): 35-37.