More people aged above 60 were sent to prison and the Drug Rehabilitation Centre (DRC) last year.
Of the 9,471 prison admissions last year, 486 involved prisoners aged above 60, statistics released by the Singapore Prison Service showed yesterday.
This would be the first time in at least 10 years that their numbers have risen above 400.
Similarly, the number of such admissions to the DRC last year also jumped by 45 per cent to 29 - the largest such intake in the last eight years.
The increased intake in both the prison and the DRC contributed to a rise in the proportion of inmates above the age of 60. They made up 8.9 per cent of the prison population as at Dec 31 last year, up from 6.1 per cent in 2016.
In the DRC, they comprised 2.9 per cent of the population, up from 2.1 per cent in 2016.
This trend is a reflection of Singapore's ageing population, said sociologist Tan Ern Ser.
The latest statistics also showed a positive trend, with more offenders staying out of trouble with the law in the first two years after their release.
The overall recidivism rates hit a six-year-low of 23.7 per cent for the cohort released in 2016.
This rate could be reduced further by making sure inmates were personally committed to change, said the prison service.
On top of that, it said, they should receive help to find work and accommodation, as well as family and community support.
To help rehabilitate offenders in a community setting, more of them have been placed in community-based schemes where they are supervised by prison officers while being out in the community, said the prison service.
There were 1,098 inmates who served the tail-end of their sentences on the Community-Based Programme (CBP) last year, an increase of 15.4 per cent from the year before.
Community-based schemes include the Day Reporting Order scheme, where offenders are free to go out but have to report back regularly to prison officers.
The 1,098 placed on the CBP last year constituted the largest number in the last three years. They served out their sentences in halfway houses, on home detention or on work release schemes.
Almost all prisoners completed the programme, and the completion rate for last year's cohort reached a three-year high of 98.5 per cent.
More offenders also took part in a supervised aftercare regime after serving out their sentences, with 734 inmates placed on the mandatory aftercare scheme, more than double the number from the year before.
Such correction programmes prepare inmates for their release by helping them transition out of a prison setting, said Superintendent of Prisons Karen Lee, who oversees community-based schemes as the deputy director of the Community Corrections Command.
She said these programmes allowed offenders to practise skills learnt in prison, while being supervised by prison officers whom they must regularly report to.