The kind of rent allowance the women received is paid to people on welfare and low incomes who would otherwise be unable to pay for private accommodation.
It subsidises part of the rent up to certain limits. The increasing reliance of householders on the private rented market, and the accompanying rises in rents, mean the demand for the allowance has been rising sharply.
Recipients include people who are unemployed, ill and lone parents.
Last year, almost 42,000 people received the payment at a cost of over £100 million.
The deaths of the four women "highlight the fact that old people are vulnerable and invisible in our society and often retreat into their own homes for long periods," the Fine Gael spokesman on health and children, Mr Gay Mitchell TD, said last night.