The Progressively Lowered Stress Threshold Model (PLST) can provide a frame or reference to understand and reduce the challenging behaviors associated with Alzheimer's disease and related dementias (ADRD). According to the PLST, people with ADRD have difficulties receiving, processing, and responding to environmental stimuli. These difficulties are the direct result of the progressive deterioration in cognitive, affective, and functional abilities that accompany dementia. Severity and frequency of behavior varies based upon the environmental stimuli and the person's stage of dementia. The more advanced the stage of dementia the more behaviors typically present.


There are many internal and external stress inducers that a person with dementia experiences on a daily basis. These stress inducers are thought to be at the root of behavioral disturbances such as hitting, resisting care, yelling, anxiousness, pacing, and sundowning.


A stress inducer can be internal such as:

  • Unmanaged pain or discomfort
  • Fatigue
  • Hunger
  • Unmet quality of life needs such as the need for attention, love, intimacy, success, friendship, purpose etc.
  • Impaired ability to communicate and express needs
  • Impaired ability to be understood
  • Negative feelings such as feeling like a failure, unwanted, lonely, or scared

A stress inducer can come from an external source such as:

  • Environmental distractions
  • Noise overload
  • An impatient, unskilled caregiver

Often there is a connection between the external environment and the internal feeling. For example, a caregiver may perform self-care on "the patient" with the sole intent of getting "the patient" clean. If the only intent of this ADL experience is "cleaning the patient" the person will likely have a negative response such as feeling like an inanimate object in the middle of a task, feeling helpless and unimportant. This then can trigger a negative behavior.


If we think about the typical day of a person with dementia, there are many likely stressors that pile up on one another. I firmly believe that this layering of stressors can cause the sundowning event.


Let's explore what can be a typical day for a person functioning in Allen Level 3:

  • A poor night's sleep
  • A 15-minute ADL experience as previously described
  • Sitting for over an hour waiting for breakfast
  • Sitting in a large, noisy, crowded, overstimulating dining room
  • Experiencing difficulty self-feeding
  • Urinating or defecating in pants and waiting to be cleaned up
  • Sitting in an activity that is far too high level and therefore it becomes "noise"
  • Wandering alone throughout the hallways and at every corner, being told to "leave that alone" or to "go sit down"
  • Feeling pain from arthritis but being unable to ask for pain medications
  • Feeling embarrassed, violated, and uncomfortable when showered naked by a stranger in a cold, scary room
  • Not being engaged socially, comforted, or loved throughout the day
  • Never feeling like a success in anything you do
  • And on and on . . .

If you experienced a day with this amount of stress would you have a "melt down" by dinner time? I would. This is what likely happens to this individual. After the layering of all of these stressors the person exceeds their stress threshold and has a melt down or in other words "sundowns."


At a 120-bed SNF designed exclusively for persons with ADRD of all stages in which I was the Director of Well Being on a full time basis, I worked with the DON on proactive methods to reduce stressors. We found a significant reduction in the amount of sundowning our residents experienced compared to the average SNF and we also saw a significant reduction for residents who experienced daily sundowning at a previous facility.


Our plan to reduce internal and external stress inducers was to:

  • Love on the residents every single day and let them know how important they were to our well-being and to the well-being of others. Our administrator would begin every daily meeting by asking us "what difference did you make in the life of a resident today?" This continued to emphasize the importance of striving for emotional well-being.
  • Create feelings of importance and success through meaningful and successful ADL and activity experiences (at the root of this is activity gradation to match Allen level).
  • Proactively manage pain by having routine pain med orders vs PRN for those in need, by offering whirl pool baths and massage, and by keeping the residents moving.
  • Minimize sensory overload with no overhead paging and radios and televisions used at selective times as a part of the activity program only.
  • Provide frequent quiet or rest periods throughout the day on a planned schedule. For example, at 10:00 a.m. and 2:00 p.m., a person who was known to sundown or was at risk for sundowning would be brought to a quiet room for a 15-minute hand massage or the person napped (the choice was made on personal preference).
  • Create small dining spaces in which the noise level and other distractions were minimized and closely monitored.
  • Use consistent caregivers who developed a loving, safe relationship with the resident—the DON supported the concept of not rotating staff.
  • Make certain the bath environment was warm and inviting.
  • To train all staff in dementia care (e.g., best communication, provision of positive feedback) and to use care approaches that match Allen level.
  • Make sure residents participated in a significant number of small and large activity groups, balanced with rest periods, each day. These activities matched their interests. One of the benefits of the high level of meaningful activity was good sleep patterns. Our residents slept well at night because they were quite active throughout the day.
  • Implement bowel and bladder programs and the DON closely monitored.
  • Refer to therapy when a person exhibited behaviors that interfered with function or safety.

These are some of the program elements that were designed, implemented, and monitored. I realize it takes a village to implement a plan as comprehensive as this. However, you may begin by using one or two of these ideas and expand your plans as you gain agreement and partnership from others.


People with ADRD do not have to be victims of these behaviors. Proactive plans such as the one described can greatly reduce the frequency and severity of behavior problems. The PLST helps us to identify the potential behavior triggers as related to internal or external stress inducers. If we can proactively reduce stress, we can greatly reduce negative behavior—thereby reducing burden on the caregiver and increasing the quality of life, function, and safety of the resident/client. This is the path to reimbursement for OT/PT/ST to intervene.


Reference: Hall, G., Buckwalter K. (1987). Progressively lowered stress threshold: A conceptual model of care of adults with Alzheimer's disease. Archives of Psychiatric Nursing, 1, 399–406.