[¶ 1] Joseph A. Roy appeals from a decision of a Workers’ Compensation Board hearing officer (Knopf, HO) discontinuing his total incapacity benefits. Roy contends that the hearing officer erred in interpreting 39-A M.R.S. § 201(5) (2007) to require that his benefits be terminated because he suffers from a subsequent, non-work-related medical condition that is totally disabling, even though he also suffers continuing total incapacity as a result of his work injuries. We vacate the hearing officer’s decision.
I. CASE HISTORY
[¶ 2] Roy, a long-time employee of Bath Iron Works (BIW), suffered an injury to his lower back in 1987 and a neck injury in 1994. In prior decrees, Roy was awarded ongoing partial (38%) incapacity benefits apportioned equally to each injury.
[¶ 3] Roy filed a petition for review in 2005, seeking increased partial incapacity benefits at varying rates from November 1, 2004, until June 9, 2005, and total incapacity benefits thereafter. He alleged increased incapacity because his 1994 neck injury had become worse.
[¶4] The parties do not dispute that Roy continues to suffer effects from both the 1987 and 1994 work injuries. Roy also suffers from health problems that are not directly related to his work injuries, including pulmonary disease, diabetes, cardiac problems, and liver disease. The cardiac and liver problems post-date both work injuries.
[¶ 5] The hearing officer found that Roy became totally incapacitated on June 9, 2005, as a result of the neck and back conditions. She further concluded, however, that as of March 6, 2006, Roy’s liver condition caused him to be totally incapacitated “irrespective of the ongoing effects of the work-related injuries.” She determined that because the liver condition post-dated both work injuries, 39-A M.R.S. § 201(5) required that “as long as Mr. Roy is totally incapacitated for his nonwork-related liver condition, he is not entitled to workers’ compensation benefits.”
[¶ 6] Accordingly, the hearing officer granted the petition for review in part and awarded Roy partial incapacity benefits at varying rates from November 1, 2004, to June 9, 2005; total incapacity benefits from June 9, 2005, until March 6, 2006; and terminated his benefits after March 6.
[¶ 7] Roy filed a petition for additional findings of fact and conclusions of law. The hearing officer issued an amended decree that adopted findings proposed by BIW but did not alter the result except for the apportionment of responsibility to pay Roy’s benefits.
[¶ 8] Roy filed his petition for appellate review, which we granted pursuant to 39-A M.R.S. § 322 (2007) and M.R.App. P. 23. Roy contends that while section 201(5) relieves the employer of liability for a subsequent nonwork-related injury or disease that is not causally connected to a previous compensable injury, it does not relieve the employer of responsibility for a co-existing total incapacity caused by work-related injuries.
II. LEGAL ANALYSIS
[¶ 9] Title 39-A M.R.S. § 201(5) provides:
5. Subsequent nonwork injuries. If an employee suffers a nonwork-relat-ed injury or disease that is not causally connected to a previous compensable injury, the subsequent nonwork-related injury or disease is not compensable under this Act.
*967This provision was first enacted by the Legislature in 1991 in identical language as part of the last reform effort before the wholesale repeal and reenactment of the Workers’ Compensation Act in 1992. P.L. 1991, ch. 615, § D-3 (codified at 39 M.R.S.A. § 51(4) (Supp.1992)).
[¶ 10] The “primary purpose in statutory interpretation is to give effect to the intent of the Legislature.” Arsenault v. Sec’y of State, 2006 ME 111, ¶ 11, 905 A.2d 285, 287-88. When a statute is not ambiguous, we interpret the statute directly, without applying rules of construction or examining legislative history or administrative interpretation. See McGee v. Sec’y of State, 2006 ME 50, ¶ 18, 896 A.2d 933, 939-40; Cobb v. Bd. of Counseling Prof'ls Licensure, 2006 ME 48, ¶ 13, 896 A.2d 271, 275. We look to legislative history and other extraneous aids in interpretation of a statute only when we have determined that the statute is ambiguous. Darling’s v. Ford Motor Co., 2003 ME 21, ¶ 7, 825 A.2d 344, 346.
[¶ 11] The language of section 201(5) is not ambiguous. In concise terms, it provides that when an injured employee is receiving compensation for a work injury, any subsequent nonwork-related injury is not compensable. That means that a subsequent nonwork injury that is not causally related to work cannot increase the level of or extend the duration of workers’ compensation benefit payments. Section 201(5) says nothing about reducing or eliminating payments to disabled workers for their work-related injuries. If the Legislature had a purpose that subsequent nonwork-related injuries should reduce or eliminate compensation for work-related injuries, section 201(5) would have been written differently. The hearing officer erred in reading section 201(5) to require that a subsequent disabling condition must terminate the compensation paid to a worker who is also totally incapacitated because of his work injuries.
[¶ 12] We first addressed the impact of subsequent nonwork injuries under the new provisions of the Workers’ Compensation Act in Mushero v. Lincoln Pulp & Paper Co., 683 A.2d 504 (Me.1996). There, the employee suffered a work-related heart attack and a subsequent nonwork-related heart attack. Id. at 505. We construed the former subsection Slid)1 to require that for a subsequent nonwork injury to be compensable, the previous work injury “must in some way bring about or set into motion a sequence of events or conditions that cause the subsequent injury.” Id. at 506. Because the hearing officer found no causal connection between the work-related heart attack and the non-work-related heart attack, we affirmed the reduction of Mushero’s benefits by the percentage of incapacity attributable to the subsequent nonwork heart attack. Id.
[¶ 13] In Pratt v. Fraser Paper, Ltd., 2001 ME 102, ¶ 2, 774 A.2d 351, 353 the employee suffered a work-related knee injury and a subsequent, nonwork-related heart attack. Considering the knee injury alone, the hearing officer found that Pratt was capable of full-time semi-sedentary work, but based on the totality of both conditions, the hearing officer determined that he was totally incapacitated. Id. ¶ 6, 774 A.2d at 353-54. The hearing officer awarded total incapacity benefits and reduced the benefits by the portion of incapacity attributable to the heart attack. Id. We vacated that decision because, when *968considering the work-related injury alone, Pratt retained some work capacity; thus, he was not entitled to an award of benefits pursuant to the total incapacity statute. Id. ¶ 15, 774 A.2d at 356. We reasoned that section 201(5) “requires the Hearing Officer to separate out the effects of the subsequent nonwork injury in calculating the amount of benefits and in determining whether the compensation level for the benefits is governed by the partial incapacity section or the total incapacity section.” Id. ¶ 12, 774 A.2d at 355. Because he proved the unavailability of work, Pratt was awarded 100% partial incapacity benefits, with a reduction commensurate to the subsequent nonwork-related injury. Id. ¶ 15, 774 A.2d at 356.
[¶ 14] In Bernier v. Data General Corp., 2002 ME 2, ¶¶ 2, 5, 787 A.2d 144, 146, the employee continued to suffer the effects of a 1978 work injury to her wrist when she more seriously injured the wrist in a nonwork-related accident. The hearing officer did not apply section 201(5), and awarded partial incapacity benefits because the work injury continued to be a substantial factor in her incapacity. Id. ¶ 5, 787 A.2d at 146. We determined that it was error to award benefits without applying section 201(5) and separating out the effects of the nonwork injury. Id. ¶ 12, 787 A.2d at 148.
[¶ 15] These opinions applying section 201(5) or its predecessor support the view that the purpose of section 201(5) is to assure that the impact of subsequent nonwork-related injuries is separated from the impact of work injuries for which benefits are paid, so that subsequent nonwork injuries do not increase the level or duration of workers’ compensation benefits paid for work injuries. Nothing in section 201(5) requires termination of workers’ compensation benefits for which a worker is qualified because of a subsequent non-work injury.
[¶ 16] The hearing officer erred in applying section 201(5) to require termination of a totally incapacitated worker’s benefits paid for work injuries because a subsequent nonwork injury was also totally incapacitating.
The entry is:
The decision of the hearing officer is vacated, remanded for further proceedings consistent with this opinion.
. We stated in a later case that "[bjecause the language of former subsection 51(4) and current subsection 201(5) are identical, our interpretation in Mushero also governs our interpretation of subsection 201(5).” Pratt v. Fraser Paper, Ltd., 2001 ME 102, ¶ 8 n. 3, 774 A.2d 351, 354.