decrease in noninterest income, primarily due to a $4.7 million decrease in gain on sale of loans, and a $155,000 increase in the provision for loan losses, partially offset by a $1.3 million increase in net interest income and a $1.9 million decrease in noninterest expense.
Interest and Dividend Income. Interest income increased $939,000, or 15.4%, to $7.0 million for the nine months ended September 30, 2022 compared to September 30, 2021. Interest income on portfolio loans increased $841,000, or 14.6%, to $6.6 million as of September 30, 2022. The average balance of portfolio loans during the nine months ended September 30, 2022 increased $40.0 million to $222.6 million, compared to the nine months ended September 30, 2021. The increase in average portfolio loans outstanding was primarily concentrated in one to four family owner-occupied mortgage loans, nonresidential mortgage loans, multifamily loans, and land and construction loans. The average yield on loans decreased 25 basis points to 3.94% for the nine months ended September 30, 2022 from 4.19% for the nine months ended September 30, 2021. The average balance of loans held for sale decreased $7.0 million during the nine months ended September 30, 2022 compared to the same nine month period in 2021, while the average yield on loans held for sale increased 147 basis points, to 4.02% for the nine months ended September 30, 2022 from 2.55% for the same nine months in 2021.
Interest income on securities increased $26,000, or 46.0%, for the nine months ended September 30, 2022. The yield on securities increased 67 basis points due to higher market interest rates. The average balance of securities decreased $1.6 million to $7.3 million at September 30, 2022. The investment securities portfolio is composed of monthly adjustable-rate securities tied to the one month T-Bill, one month LIBOR or the one year Treasury index. Interest income on other interest-earning assets increased $122,000, or 282.4%. The yield on other interest-bearing assets increased 123 basis points due to a higher dividend rate paid on FHLB stock and the increase in short term interest rates.
Interest Expense. Total interest expense decreased $313,000, or 23.7%, to $1.0 million for the nine months ended September 30, 2022 from $1.3 million for the nine months ended September 30, 2021. Interest expense on deposit accounts decreased $102,000, or 12.9%, to $894,000 for the nine months ended September 30, 2022 compared to the nine months ended September 30, 2021. The decrease in deposit expense between comparable periods in 2022 from 2021 was primarily due to an 11 basis point decrease in the average cost of deposits primarily due to lower market interest rates.
Interest expense on savings increased $177,000, or 236.0%, during the nine months ended September 30, 2022 compared to the nine months ended September 30, 2021, due to an increase in the average balance of savings accounts of $24.6 million. The average cost of savings accounts increased 24 basis points compared to the same period ended September 30, 2021. Interest expense on interest-bearing demand accounts increased $5,000, or 15.2%. The average cost of interest-bearing demand deposits increased 1 basis point to 15 basis points. The average balances in interest-bearing demand accounts increased $3.9 million during the nine months ended September 30, 2022 compared to the same period ended September 30, 2021. Interest expense on certificates of deposit decreased $79,000, or 11.6%. The average cost of certificates decreased 47 basis points to 0.89%. The average balance of certificates of deposit increased $24.2 million to $90.8 million for the nine months ended September 30, 2022 compared to the same period ended September 30, 2021.
Interest expense on FHLB advances decreased $416,000, or 78.4%, to $114,000 for the nine months ended September 30, 2022 from the nine months ended September 30, 2021. The average balance of advances decreased $26.0 million, or 76.1%, for the nine months ended September 30, 2022. The average cost of FHLB borrowings decreased 21 basis points to 1.86% for the nine months ended September 30, 2022 from 2.07% for the same period in 2021.
Net Interest Income. Net interest income increased $1.3 million, or 26.3%, for the nine months ended September 30, 2022 compared to the same period in 2021. The interest rate spread increased to 3.06% for the nine months ended September 30, 2022 compared to 2.62% for the nine months ended September 30, 2021. The net interest margin increased 38 basis points to 3.17% at September 30, 2021 compared to 2.79% at September 30, 2021.
Provision for Loan Losses. Based on our analysis of the factors described in “Critical Accounting Policies – Allowance for Loan Losses” we recorded a provision for loan losses of $155,000 for the nine months ended September 30, 2022. The allowance for loan losses was $1.8 million, or 0.70% of total loans, at September 30, 2022, compared to $1.7 million, or 0.81% of total loans, at September 30, 2021. The Company had no net charge-offs during the nine-month period ended September 30, 2021. Given the growth in the loan portfolio during the nine months ended September 30,2022, an increase in the allowance was warranted. Total past due loans were $54,000, or 0.02% of loans at September 30, 2022. The Company had net recoveries of $6,000 during the nine-month