Your feature (Four daily steps to a younger smarter brain, Train your brain supplement, 13 October) says “Those born in 1900 would have been lucky to reach their 50th birthday. Today, life expectancy in many countries exceeds 80.” This may trick readers into thinking that men and women are now living an extra 30, 40 or more years, but one has only to look at tombstones or burial registers to realise that there were many people in their 60s and 70s, and older, in previous centuries.

The truth is that expectation of life at birth is skewed by infant mortality. If you survived your first year, you might live a normal lifespan. It is not doctors but the provision of clean water, clean lavatories and proper drains in overcrowded towns that has made the difference to expectation of life at birth.

Jacqueline Sarsby

Uley, Gloucestershire

• Join the debate – email guardian.letters@theguardian.com

• Read more Guardian letters – click here to visit gu.com/letters

• Do you have a photo you’d like to share with Guardian readers? Click here to upload it and we’ll publish the best submissions in the letters spread of our print edition