Kidney Function

The kidneys serve several purposes in the waste management and proper functioning of the human body (National Institute of Diabetes and Digestive and Kidney Diseases, 1998):

• They remove wastes from blood through excretion of 1.5 to 2.5 liters of urine every day; in this process, they regulate levels of sodium, phosphorus, potassium, and other essential nutrients.
• They secrete the hormone erythropoietin (EPO), which stimulates the bone marrow to make red blood cells.
• They secrete the hormone renin, which regulates blood pressure.
• They release vitamin D, which helps maintain calcium for bones and normal chemical balance in the body.

Renal failure can be either "chronic," resulting from systemic disease, or "acute," occurring suddenly as a result of incidents such as abdominal trauma, bacterial food poisoning, or drug overdose. Common causes of CRF include diabetes, hypertension, lupus, urologic diseases, and various kidney-specific diseases. When CRF becomes so severe that the patient cannot survive with current kidney function and dialysis or kidney transplant is required, a diagnosis of ESRD applies. This report focuses on ESRD.

The gradual deterioration of the function of the kidneys as they become less able to maintain steady volume and concentration of bodily fluids can, in turn, lead to high blood pressure and edema (fluid in the tissues) as the first symptoms of renal failure. As deterioration progresses, additional symptoms may include fatigue, headaches, nausea, vomiting, decreased appetite, itching, and increased tendency to bleed (Faber and Wilde, 1993). Physiological laboratory indicators of CRF include (National Institute of Diabetes and Digestive and Kidney Diseases, 1998):

• Elevated serum creatinine levels (i.e., waste product of muscle activity, normally filtered out by the kidneys). The definition of abnormal levels depends on many factors, such as disease, sex, age, and muscle mass. Normal levels are generally 0.6 to 1.2 mg/dL. Patients with Type 2 diabetes may have acceptable levels as high as 6 mg/dL.
• Reduced creatinine clearance. Indicates how fast kidneys remove creatinine from blood. Levels below ~85 mL/min are abnormal. This is the most commonly used indicator of glomerular filtration rate (GFR).
• Elevated blood urea nitrogen (BUN). Impaired kidneys cannot filter urea, a protein waste product. Levels >20 mg/dL are abnormal.
• Proteinuria (i.e., elevated protein in urine). Kidneys fail to separate protein from waste. Levels >150 mg over 24 hours indicate proteinuria.

Causes of ESRD

There are several systemic diseases that can lead to impaired kidney function, and ultimately, to kidney failure. The most common among these is diabetes, accounting for 33 percent of prevalent cases, followed by hypertension (24 percent), glomerulonephritis (17 percent), and cystic kidney disease (5 percent) (United States Renal Data System, 1999a). Among incident cases in 1997, the top three causes were diabetes (42 percent), hypertension (25 percent), and glomerulonephritis (9 percent). Most of these diabetes cases are adult-onset (Type 2) diabetes. Other causes of ESRD include interstitial nephritis, neoplasms, and AIDS-related nephropathy (United States Renal Data System, 1999a).

However, the rates at which these diseases cause ESRD differ among age groups. Diabetes is rare (1.6 percent) among ESRD patients 20 years and younger; this age group is most often afflicted with glomerulonephritis (30.1 percent) and cystic/congenital kidney disease (26.2 percent). Among the oldest patients (over 65 years), the most common cause is diabetes (37.3 percent), followed closely by hypertension (35.4 percent) (United States Renal Data System, 1999a).

Treatments for CRF

For those patients with progressive CRF who are not yet in need of dialysis, there are no treatments to prevent the onset of ESRD, only to delay it. The approach will differ depending on the causal disease. The primary treatment approach for all patients is one of dietary therapy to ease the stress on the malfunctioning kidneys. The traditional approach is a protein-, potassium-, and phosphorus-restricted diet. Because the kidneys cannot process protein correctly, intake of normal levels of protein-containing foods (which are also usually high in potassium and phosphorus) can result in accumulation of nitrogen-containing waste products, metabolic acidosis, hyperphosphatemia, and hyperkalemia (Mitch and Maroni, 1998). Recommendations for protein limits range from 0.8 to 1.0 g/Kg of body weight per day (Mitch and Maroni, 1998; Morrison, 1997). The major risk of such a low-protein diet is malnutrition, which can be avoided by taking nitrogen-free amino acid supplements. Maintenance of normal serum phosphorus levels can prevent renal osteodystrophy and progression of renal failure, so careful dietary control is recommended to maintain serum phosphorus levels between 3.5 and 4.0 mg/dL. Foods rich in phosphorus, such as eggs, dairy products, and red meat, are generally avoided (Morrison, 1997). In addition, nephrologists frequently prescribe medications that act as phosphate binders to reduce serum phosphorus (Witten, 1999).

Diabetic patients can also slow progression of disease by monitoring blood glucose carefully. Patients with hypertension need to monitor blood pressure and avoid foods, such as salt, that may increase blood pressure. Physicians frequently prescribe ACE (angiotension converting enzyme) inhibitors for diabetics-even those with normal blood pressure readings-to slow the progression of diabetic kidney disease and reduce proteinuria (Witten, 1999).

For patients with ESRD, it is necessary to provide a replacement for the nonfunctional kidneys in order to filter waste material out of the blood. There are currently three primary options for therapy. The first, and most established, is hemodialysis (HD). This provides cleansing of the blood using an external device that includes a dialyzer to filter waste products out of the blood; dialysate, a liquid that collects the waste products; and a dialyzer for exposure to dialysate across a semipermeable membrane that facilitates molecular diffusion. The use of this external device requires the creation of an arteriovenous (AV) fistula (internal joining of artery and vein) or arteriovenous graft (artificial blood vessel used to join artery and vein), usually in the patient's forearm, or-for temporary access or when other options for access have been exhausted-a cuffed or noncuffed double-lumen percutaneously inserted central venous catheter may be inserted into the jugular vein, subclavian vein, or femoral vein. These methods allow blood to flow out of the arm, through the dialyzer, and-having had toxins removed-back into the patient. The average treatment time is 3 to 4 hours every 2 to 3 days (Kidney Dialysis Foundation, 1999; Witten, 1999; National Institute of Diabetes and Digestive and Kidney Diseases, 1994). Treatment can be provided at a dialysis center ("in-center" HD) or at home.

Peritoneal dialysis (PD), a newer approach, is the internal cleansing of blood using the peritoneal membrane of the abdominopelvic wall as the dialyzer. This approach requires a permanent catheter inserted into the abdomen. The dialysate is passed through the catheter into the patient's abdomen, where it collects waste products from capillaries in the peritoneal membrane. High glucose levels in the dialysate cause water to be drawn from the blood in the capillaries by osmosis, and waste products are removed by convection and diffusion (Kidney Dialysis Foundation, 1999). The dialysate remains in the abdomen for several hours, then is drained, to be replaced with fresh dialysate (National Institute of Diabetes and Digestive and Kidney Diseases, 1994). This can be done using three methods:

1.

Continuous ambulatory peritoneal dialysis (CAPD). the blood is always being cleaned. The patient drains solution from a bag through a small permanent peritoneal catheter into the peritoneal cavity several times every day. After the solution is drained, the patient disconnects from the now empty bag, wraps the catheter tubing, and covers it with a dressing to prevent infection (Witten, 1999). Each cycle takes 4 to 6 hours. The continuous nature of this method leads to better clearance of poorly dialyzable compounds, especially phosphate (Morrison, 1997).

2.

Continuous cycling peritoneal dialysis (CCPD). A machine automatically fills and drains dialysis solution into the peritoneal cavity through the permanent peritoneal catheter at night while the patient sleeps. Total cycle time is 10 to 12 hours nightly.

3.

Intermittent peritoneal dialysis (IPD). This process is similar to CCPD, but is usually done in a hospital, and it takes longer than CCPD (up to 24 hours), but is done less often (3 to 4 times a week). This treatment option is rarely used in the United States today.

Current statistics from the USRDS indicate that in-center hemodialysis continues to be the most often used modality of dialysis treatment in the United States, as it has been for the past 10 years. It has consistently been the treatment given to 80 to 85 percent of patients undergoing dialysis. Most recent figures estimate that approximately 85 percent use in-center HD, 9 percent use CAPD, 4 percent use CCPD, and 1 percent use home hemodialysis. The use of CCPD has been steadily rising for the past 5 years, replacing CAPD for many patients, but not affecting the usage of in-center hemodialysis (United States Renal Data System, 1999a). These figures are in sharp contrast to some other countries, such as Canada, Australia, and Denmark, where at-home peritoneal dialysis is the favored method (United States Renal Data System, 1999a). The choice of treatment option is currently being studied as part of a multiyear international research project titled "Dialysis Outcomes and Practice Patterns Study."

The third option, and the only alternative to dialysis, is kidney transplant, either from a live or decedent donor. Decedent donors are more common, comprising approximately three-quarters of all transplants in the United States (United Network for Organ Sharing , 1997). Live donors are most often blood relatives of the patients, in order to achieve better HLA (human leukocyte antigen) matching, and thus reduce the risk of kidney rejection. The major risks of kidney transplant are rejection of the kidney and graft failure. Patients must take immunosuppressants (such as corticosteroids, azathioprine, and cyclosporine) for the rest of their lives to prevent rejection (Morrison, 1997). The necessity of immunosuppression generally limits the patients who are eligible for transplant to those who are young and/or in reasonably good health, although improvements in the procedure are expanding the potential patient pool. Conditions and situations that limit the patients who are eligible for transplant also include poor cardiac or vascular status, recent (within 1 year) malignancy, unstable psychological status, and current misuse of alcohol or drugs. In addition, kidney transplantation is limited by the availability of viable organs for transplantation.

Transplantation of the kidney can be done either alone or in conjunction with other organs, most commonly the pancreas. Prevalence estimates from USRDS indicate that approximately 28 percent of all ESRD patients have a functioning transplant (United States Renal Data System, 1999a). Recent survival estimates from the United Network of Organ Sharing (UNOS) suggest a 1-year graft survival rate of 85.6 percent and a patient survival rate of 94.9 percent. Approximately 38 percent of patients experience rejection episodes during the first 6 months after transplant, and 12 percent undergo multiple transplants due to rejection or graft failure (United Network for Organ Sharing, 1997).

Epidemiology

The most recent calculations by the USRDS indicate that 110 of every 100,000 people have ESRD. About 29 of every 100,000 are diagnosed with ESRD each year. The rate of new diagnoses (i.e., incidence) has been growing, most recently at an average rate of 5 percent per year since 1992 (United States Renal Data System, 1999a). Men are diagnosed with ESRD more often than are women (131 per 100,000 versus 93 per 100,000), possibly a result of the higher prevalence of some of the causative diseases in men. African-Americans make up a disproportionately large percentage of the ESRD population, making up 32.1 percent of all ESRD patients (while African-Americans make up 12.6 percent of the population as a whole). This may be due to a higher incidence of diabetes and hypertension in this population (United States Renal Data System, 1999a). Sixty-one percent of ESRD patients are Caucasian, and the other 6.9 percent are minorities other than African-Americans.

The average age of all prevalent cases of ESRD is 56 years. On the other hand, the average age of new incident cases in 1997 was 61 years. The reason for this age increase is unclear. Persons aged 45 to 64 made up the largest proportion of ESRD patients in 1997, at 38.8 percent. Although patients with ESRD are generally in the older age groups, it is important to assess working ability, since patients under age 45 make up almost 28 percent of all prevalent cases, and just over 16 percent of incident cases in 1997 (United States Renal Data System, 1999a).

Determining the prevalence of CRF overall is more difficult, because many people who suffer from earlier stages of the disease do not seek treatment or are not diagnosed properly; therefore, reliable statistics are not available.

The average survival time of ESRD patients (with treatment) is between 19 and 47 percent of average survival time of the general age- and sex-matched population. First year mortality for incident ESRD patients in 1996 was 19.8 per 100 patient-years at risk (adjusted for age, sex, and primary causal disease). Although incidence of ESRD is higher in the African-American population than in the Caucasian population, first-year death rates have been consistently higher among Caucasians (23.3 percent versus 18.8 percent in 1996). However, this racial difference has been steadily decreasing, from 12.6 per 100 person-years at risk in 1986 to 4.5 per 100 person-years at risk in 1996, as the Caucasian death rate has decreased more rapidly than has that of African-Americans. Patients with diabetes demonstrate the highest first-year mortality rate of any single diagnostic group (23.2 per 100 person-years at risk). Men and women have nearly equal mortality rates (United States Renal Data System, 1999a).

History of Social Security Disability Coverage

After the establishment of the retirement insurance program under the Social Security Act of 1935 (Public Law (P.L.) 74-271), serious thought was given to whether that program should be expanded to provide wage related cash benefits to workers who become permanently and totally disabled before age 65 and to their dependents. During the period from 1940 to 1950, the Social Security Board and its 1946 successor, the Social Security Administration, recommended in their annual reports that benefits be provided to permanently and totally disabled workers and their dependents as part of the Social Security system. The 1948 Advisory Council on Social Security to the Senate Finance Committee made specific recommendations for the payment of Social Security benefits to disabled workers (S. Doc. No. 162, 80^th Cong., 1^st sess. (1948)). However, the Social Security Act Amendments of 1950 (P.L. 81-734) made no provision for disability insurance benefits. Instead, provision was made for grants in aid to the States for public assistance to permanently and totally disabled, needy individuals. The Social Security Amendments of 1952 (P.L. 82-590) included a measure providing for the establishment of a "disability freeze," but the measure was not affirmed prior to July 1953 and did not become operative.

The Social Security Amendments of 1954 (P.L. 83-761) created the first Social Security disability program with the institution of the disability freeze. As defined by the 1954 Amendments, disability meant, "inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment which can be expected to result in death or to be of long-continued and indefinite duration." Monthly disability insurance benefits were first established by the Social Security Amendments of 1956 (P.L. 84-880). Benefits were provided for disabled insured workers between the ages of 50 and 65 and for disabled children of retired or deceased insured workers if the child was disabled before age 18. The Social Security Amendments of 1958 (P.L. 85-840) expanded the program by including benefits for dependents of disabled workers. The Social Security Amendments of 1960 (P.L. 86-778) removed the minimum age requirement of 50 years for disability insurance beneficiaries. The Social Security Amendments of 1965 (P.L. 89-97) deleted the requirement that the impairment be of "long-continued and indefinite duration" and substituted in its place a requirement that the impairment "be expected to last for a continuous period of not less than 12 months."

The Social Security Amendments of 1967 (P.L. 90-248) added language to the definition to make it clear that a claimant may be found disabled "only if his physical or mental impairment or impairments are of such severity that he is not only unable to do his previous work but cannot, considering his age, education, and work experience, engage in any other kind of substantial gainful work which exists in the national economy, regardless of whether such work exists in the immediate area in which he lives, or whether a specific job vacancy exists for him, or whether he would be hired if he applied for work." The Secretary was also given specific statutory authority to prescribe, by regulations, criteria for determining when services performed or when earnings from services demonstrate ability to engage in substantial gainful activity (Social Security Administration, 1999a and 1999b).

The Social Security Amendments of 1972 (P.L. 92-603) created the Supplemental Security Income program for the Aged, Blind and Disabled. The definition of disability used for disability insurance benefits was carried over into the SSI program, with a modification for SSI claimants under age 18. The 1972 Amendments also extended health insurance coverage to people who had chronic renal disease and required dialysis (including peritoneal dialysis) or kidney transplantation (Solomon, 1986).

The Social Security Amendments of 1978 made significant modifications in the chronic renal disease provisions of the Medicare program. This law designated it as the End-Stage Renal Disease program and established renal disease network areas and a national ESRD medical information system and provided Medicare payment to providers of ESRD services (United States Congress, 1977). Additional amendments have been added to the Act since then, including the addition of vocational rehabilitation programs and work incentive plans.

Social Security Disability Insurance

The SSA administers two programs that provide benefits based on disability: the Social Security Disability Insurance program (title II of the Social Security Act) and the Supplemental Security Income program (title XVI of the Act). Title II provides for payment of disability benefits to individuals who are "insured" under the Act by virtue of the Social Security tax on their earnings, as well as to certain disabled dependents of insured individuals. Title XVI provides for SSI payments to individuals (including children under age 18) who are disabled and have limited income and resources.

SSA currently defines disability as "the inability to engage in any substantial gainful activity by reason of any medically determinable physical or mental impairment(s) which can be expected to result in death or which has lasted or can be expected to last for a continuous period of not less than 12 months." SSA currently defines "substantial gainful activity," in turn, as working for pay or profit and earning more than $700 a month (Social Security Administration, 1999c).

A worker who becomes disabled must wait 5 full calendar months after disability begins before receiving SSDI benefits (Social Security Administration, 1995). SSDI provides only compensation for lost employment. It does not provide health insurance until the individual has been entitled to benefits for 24 months. In general, disabled individuals requiring health insurance can receive it either through their current or former employer, a spouse's current or former employer, or they can qualify for Medicare and, in most states, persons who receive Supplemental Security Insurance benefits are automatically entitled to Medicaid without a waiting period. Persons with ESRD qualify for Medicare based on their ESRD condition. Unless the person with ESRD chooses to perform home or self-care dialysis, there is a 3-month waiting period for Medicare. Persons who are covered under an employer group health plan have a 30-month period during which Medicare is the secondary payer (Social Security Administration, 1995).

Social Security evaluates claims for disability using a five-step sequential evaluation process. The five-step process asks the following questions:

1.

Is the individual engaging in substantial gainful activity? If the individual is working and the work is substantial gainful activity, as defined by SSA's regulations, a determination of "not disabled" is made. Otherwise, the adjudicator proceeds to step 2 of the sequence.

2.

Does the individual have a medically determinable impairment or combination of impairments that is severe, as defined in SSA's regulations? If the individual does not have an impairment or combination of impairments that is severe, a determination of "not disabled" is made. If the individual has an impairment or combination of impairments that is severe, the adjudicator proceeds to step 3 of the sequence.

3.

Does the individual's impairment(s) meet or equal the severity of an impairment listed in appendix 1 of subpart P of part 404 of the SSA regulations? If so, and the duration requirement is met, SSA finds that he or she is disabled. If not, the adjudicator proceeds to step 4 of the sequence.

4.

Does the individual's impairment(s) prevent him or her from doing his or her past relevant work, considering his or her residual functional capacity? If not, a determination of "not disabled" is made. If so, the adjudicator proceeds to step 5 of the sequence.

5.

Does the individual's impairment(s) prevent him or her from adjusting to other work that exists in the national economy, considering his or her residual functional capacity together with the "vocational factors" of age, education, and work experience? If so, and if the duration requirement is met, SSA finds that the individual is disabled. If not, the individual is determined not disabled (Proposed rules, 1999).

Different provisions are made if the individual has never performed "skilled" labor. The determination for these individuals is made as follows:

"If you have only a marginal education and work experience of 35 years or more during which you did arduous unskilled physical labor, and you are not working and are no longer able to do this kind of work because of a severe impairment(s), we will consider you unable to do lighter work, and therefore, disabled. However, if you are working or have worked despite your impairment(s) (except where the work is sporadic or is not medically advisable), we will review all the facts in your case, and we may find that you are not disabled. In addition, we will consider that you are not disabled if the evidence shows that you have training or past work experience which enables you to do substantial gainful activity in another occupation with your impairment, either on a full-time or a reasonably regular part-time basis." (CFR 20 §404.1562) (Social Security Administration, 1997a)

Many different individuals take part in this evaluation process, including the SSA's State Disability Determination Service agencies. A claimant's physician is asked to provide medical information and at times consultative examinations may be ordered. When a claimant appeals a decision denying his or her claim for disability benefits, the court may evaluate the claim using the same sequential evaluation process.

Listing of Impairments

Since 1954, there has been an established list of medical impairments which, in and of themselves, are considered sufficient to preclude any gainful activity, absent evidence to the contrary. The Listing of Impairments was published in the regulations of August 1968. Prior to that date, the regulations contained a brief list of examples of impairments that would ordinarily be considered disabling. That list in the regulations was supplemented by a listing that appeared in the Disability Insurance State Manual (DISM).

Title XVI benefits for children under age 18 began in 1974. When this new category of recipients came into being, it was recognized that the Listings then in effect (now designated Part A) would not be appropriate in all cases for evaluating disability in children. Part B of the Listings, which contain additional medical criteria that apply only to the evaluation of impairments in children under 18, was published in the regulations in March 1977 (Social Security Administration , 1999b).

Revisions to all of the impairment listings in Part A of the Listings were published in the regulations in March 1979. Additional revisions to selected impairment listings have been published between 1979 and 1999; however, the impairment listings in Part A related to CRF have not been revised since March 1979. The Listingsprovide guidelines for determining disability for a variety of impairments, both physical and mental. The Listing for adult patients with CRF, developed by a consensus panel of physicians, from section 6.02 of the Listing of Impairments reads as follows (Social Security Administration, 1998):
6.02 Impairment of Renal Function, due to any chronic renal disease expected to last 12 months (e.g., hypertensive vascular disease, chronic nephritis, nephrolithiasis, polycystic disease, bilateral hydronephrosis, etc.). With:

1.

Chronic hemodialysis or peritoneal dialysis necessitated by irreversible renal failure,

2.

Kidney transplant, consider under a disability for 12 months following surgery; thereafter, evaluate the residual impairment (see Section 6.00C), or

3.

Persistent elevation of serum creatinine to 4 mg/dL (100 mL.) or greater or reduction of creatinine clearance to 20 mL/min (29 L/24 hours) or less, over at least 3 months, with one of the following:

1.

Renal osteodystrophy manifested by severe bone pain and appropriate radiographic abnormalities (e.g., osteitis fibrosa, marked osteoporosis, pathologic fractures); or

2.

A clinical episode of pericarditis; or

3.

Persistent motor or sensory neuropathy; or

4.

Intractable pruritus; or

5.

Persistent fluid overload syndrome resulting in diastolic hypertension (110 mm. or above) or signs of vascular congestion; or

6.

Persistent anorexia with recent weight loss and current weight meeting the values in 5.08, Table III or IV; or

7.

Persistent hematocrits of 30 percent or less.

Listing 106.02 of the Listing of Impairments(Social Security Administration, 1998) regarding children with CRF reads as follows:

• 106.02 Chronic Renal Disease. With:
• Persistent elevation of serum creatinine to 3 mg. per deciliter (100 ml.) or greater, over at least 3 months; or Reduction of creatinine clearance to 30 ml. per minute (43 liters/ 24 hours) per 1.73m 2 of body surface area over at least 3 months, or Chronic renal dialysis program for irreversible renal failure; or Renal transplant. Consider under a disability for 12 months following surgery; thereafter evaluate the residual impairment (see 106.00B).

At the time these Listings were finalized, patients receiving dialysis were treated as "end-stage" patients (i.e., patients who were severely infirm and likely to die). There were few treatments available to allow these patients to live a normal, active life. Thus, all patients on dialysis were considered disabled. It was recognized, as well, that some patients not yet on dialysis might be infirm as well, if theirs was a progressive chronic kidney disease, and so the listings in sections 6.02C and 106.02A and B (above) were included.

However, because of changes in treatments, it is unclear whether those guidelines are still appropriate today, in the 1990s, and beyond. It is not the purpose of this report, however, to evaluate advances in treatment. The purpose, instead, is to determine whether the Listings are supported by evidence in the clinical literature, and if not, what combination of laboratory, clinical, functional, and demographic variables most accurately predict inability to work in adult patients with CRF.

Work Incentives

Work incentives are provided by SSA to allow disability beneficiaries to test their ability to work without losing benefits. In general, a person has at least 3 years to test the ability to work, including full disability payments during the first 9 months and a period in which disability benefits can be started again without a new application. The patient continues to receive Medicare coverage during this time (Social Security Administration, 1995). These work incentives are active for a 9-month trial period, after which SSA assesses whether the patient's earnings are "substantial." If this is the case, the patient may lose SSDI benefits after 3 more months. If earnings are not "substantial," work incentives can continue for an additional 36 months, during which SSI is received for any month during which the patient's income falls below $700 per month (Social Security Administration, 1995).

In summary, the SSDI work incentives include:

• Reimbursement for impairment-related work expenses,
• Trial work period for 9 months,
• Extended period of eligibility for 36 months if earnings are less than $700 per month,
• Continuation of Medicare coverage for 39 months,
• Continued payment under a vocational rehabilitation program, and
• Additional benefits for those patients who are blind.

However, there has been criticism that information about these work incentives is difficult for disability beneficiaries to obtain. A major obstacle to this information is the lack of vocational rehabilitation counseling. While assessment of vocational rehabilitation usefulness is a mandated part of the SSDI application process (Social Security Administration, 1997b), patients with ESRD rarely see these rehabilitation counselors, as evidenced by one statistic showing that only half of dialysis patients had contact with a vocational rehabilitation counselor (Kutner and Brogan, 1989). Critics point out that this may be due in part to Public Law 97-35, which delays Social Security funding of State vocational rehabilitation agencies until it can be proven that their use leads to substantial gainful activity for at least 9 consecutive months (Life Options Rehabilitation Advisory Council, 1994). Other potential problems with the work incentives program include patient reluctance to give up disability payments and patient ignorance about the existence of work incentives programs (Life Options Rehabilitation Advisory Council, 1997; Kapron, Nix, and Smith-Wheelock, 1996; Evans, Manninen, Garrison et al., 1983; Lundin and Lundin, 1983).