NOI for our Same-Store Community properties increased 14.0%, or $27.5 million, for the three months ended March 31, 2022 compared to the same period in 2021. The increase in property NOI was attributable to a 10.8%, or $31.4 million, increase in property rental income, partially offset by a 4.2%, or $3.9 million, increase in operating expenses. The increase in property rental income was primarily driven by a 5.3%, or $15.0 million, increase in rental rates, a $5.0 million decrease in our bad debt expense related to multifamily tenant lease receivables, a $5.7 million decrease in rent concessions, a $2.5 million decrease in occupancy loss and a 9.8%, or $3.1 million, increase in reimbursement and ancillary and fee income. Physical occupancy increased by 1.0% to 97.3% and total monthly income per occupied home increased by 9.7% to $2,322.
The increase in operating expenses was primarily driven by a 37.2%, or $1.7 million, increase in insurance expense due to increased claims, a 9.3%, or $1.4 million, increase in repair and maintenance expense due to the increased use of third party vendors, and a 7.8%, or $1.0 million, increase in utilities, which was primarily due an increase in energy costs.
The operating margin (property net operating income divided by property rental income) was 69.5% and 67.6% for the three months ended March 31, 2022 and 2021, respectively.
Non-Mature Communities/Other
UDR’s Non-Mature Communities/Other represent those communities that do not meet the criteria to be included in Same-Store Communities, which include communities recently developed or acquired, redevelopment properties, sold or held for disposition properties, and non-apartment components of mixed use properties.
The remaining 8.4%, or $20.4 million, of our total NOI during the three months ended March 31, 2022 was generated from our Non-Mature Communities/Other. NOI from Non-Mature Communities/Other increased by 305.6%, or $15.4 million, for the three months ended March 31, 2022 as compared to the same period in 2021. The increase was primarily attributable to an $18.5 million increase in stabilized, non-mature communities NOI due to operating communities acquired in 2021, partially offset by a $1.9 million decrease in sold and held for disposition communities.
Real estate depreciation and amortization
For the three months ended March 31, 2022 and 2021, the Company recognized real estate depreciation and amortization of $163.6 million and $144.1 million, respectively. The increase in 2022 as compared to 2021 was primarily attributable to communities acquired in 2021, partially offset by fully depreciated assets in 2022 and 2021.
Gain/(Loss) on sale of real estate owned
During the three months ended March 31, 2022, the Company did not recognize any gains from the sale of real estate. During the three months ended March 31, 2021, the Company recognized a gain of $50.8 million from the sale of an operating community located in Anaheim, California.
Interest expense
For the three months ended March 31, 2022 and 2021, the Company recognized interest expense of $35.9 million and $78.2 million, respectively. The decrease in 2022 as compared to 2021 was primarily due to $42.0 million of extinguishment costs from the prepayment of debt during the three months ended March 31, 2021, as compared to none for the three months ended March 31, 2022.
Inflation
Inflation primarily impacts our results of operations as a result of wage pressures and increases in utilities and repair and maintenance costs. In addition, inflation could also impact our general and administrative expenses, the interest on our debt if variable or refinanced in a high-inflationary environment, and our cost of development, redevelopment or maintenance activities including if materials are not purchased or contractually locked in advance of such increases. However, the majority of our apartment leases have initial terms of 12 months or less, which generally enables us to compensate for inflationary effects by increasing rents on our apartment homes. Although an extreme escalation in costs could have a negative impact on our residents and their ability to absorb rent increases, we do not believe this had a material impact on our results for the three months ended March 31, 2022.