Senior citizens will have more opportunities to keep their minds active, with more than 900 courses and 21,000 learning places available this year at the National Silver Academy (NSA).

This is twice the 500 courses and 10,000 places offered last year, said Senior Minister of State for Health Amy Khor at an event to celebrate the International Day of Older Persons yesterday.

The NSA offers those aged 50 and above courses in diverse areas, ranging from information technology to art, for a token fee.

More than 200 people from various senior activity centres and volunteers attended yesterday's celebrations organised by RSVP Singapore, a group that promotes volunteerism among seniors.

They penned notes of appreciation to family and friends who have been there for them, as part of the "Seniors Give Thanks!" campaign.

In addition, over 25,000 thank-you cards were distributed to 68 agencies for seniors under their care to give to their loved ones.

Said RSVP president Koh Juay Meng: "We have heard of so many senior-related initiatives where we give thanks to our seniors - they have always been the receivers.

"But perhaps now is the time for seniors to give thanks to those who have been there for them."

Mr Philip Oh, 65, who uses a wheelchair, presented a thank-you card to his friend, Mr Patrick Loh, 64. The pair met five years ago when Mr Loh, a volunteer with Willing Hearts, delivered food to Mr Oh, who lived alone, and they became good friends.

Mr Loh, who runs his own business, often drives Mr Oh around to help him run errands or to polyclinic appointments.

Dr Khor said seniors have much experience and wisdom to share and can serve as a positive force in society. The money for NSA comes from a $3 billion Action Plan for Successful Ageing launched in 2015.

It also funds efforts to build an ageing-friendly city, such as rolling out wheelchair-friendly buses.