5% did not improve and declined further treatment.Of the 413 patients who improved, 74 had a recurrence of symptoms during the observation period and their symptoms responded to rest or after resumption of the exercise program.The Morrison study shows that the outcome of impingement symptoms varies with patient characteristics. Younger patients (20 years or less) and patients between 41 and 60 years of age, fared better than those who were in the 21 to 40 years age group. This may be related to the peak incidence of work, job requirements, sports and hobby related activities, that may place greater demands on the shoulder. However, patients who were older than sixty years of age had the "poorest results". It is known that the rotator cuff and adjacent structures undergo degenerative changes with ageing.The authors were unable to posit an explanation for the observation of the bimodal distribution of satisfactory results with regard to age. They concluded that it was "unclear why (those) who were twenty-one to forty years old had less satisfactory results". The poorer outcome for patients over 60 years old was thought to be potentially related to "undiagnosed full-thickness tears of the rotator cuff". References
Anderson, D., M, (2000), Dorland’s Illustrated Medical Dictionary, 29th ed, W.B. Saunders Company, Canada, 965-967. Buschbacher, R., M, Braddom, R., L. (1994). Sports medicine & rehabilitation: A sport-specific approach. Hanley and Belfus Inc, Philadelphia. Hartley, A. (1990). Practical joint assessment: A sports medicine manual, St Louis, Sydney. Further reading
Arend CF. Ultrasound of the Shoulder. Master Medical Books, 2013.
Side effects may include:

Psychological
Depression or even suicidal ideation, as well as nightmares
Apathy or anhedonia, as well as dysphoria
Anxiety, especially of the social anxiety variant
Decreased alertness, awareness, and wakefulness
Impaired attention, focus, and concentration
Decreased desire, drive, and motivation
Fatigue or lethargy or malaise or lassitude
Sedation or drowsiness or somnolence or sleepiness
Agitation or restlessness
Cognitive and memory impairment
Derealization or depersonalization, as well as mild psychosis
Sexual dysfunction including impaired libido, desire, and drive
Physiological
Dizziness, lightheadedness, or vertigo
Miosis or pupil constriction
Xerostomia or dry mouth
Gastrointestinal disturbances such as diarrhea or constipation
Headache or migraine
Myalgia or muscle aches, arthralgia or joint pain, or paresthesia ("pins and needles")
Restless legs syndrome (RLS)
Parkinsonian symptoms such as muscle tremors, rigidity, hypokinesia, or balance or postural instability
Akathisia, ataxia, dyskinesia as well as even tardive dyskinesia, or dystonia
Bells palsy or facial paralysis
Sexual dysfunction consisting of impaired erectile dysfunction or anorgasmia
Hyperprolactinemia or excess prolactin, gynecomastia/breast enlargement in males, or amenorrhoea or absence of menstrual cycles in females
Bradycardia or decreased heart rate
Hypotension or decreased blood pressure (though this may also be considered a therapeutic benefit)
Orthostatic hypotension (also known as postural hypotension)
Hepatitis, hepatotoxicity, or liver dysfunction or damage
Pancreatitis or inflammation of the pancreas
Warm autoimmune hemolytic anemia or deficiency in red blood cells (RBCs)
Myelotoxicity or bone marrow suppression, potentially leading to thrombocytopenia or blood platelet deficiency or leukopenia or white blood cell (WBC) deficiency
Hypersensitivity such as lupus erythematosus, myocarditis, or pericarditis
Lichenoid reactions such as skin lesions or rashes
Pallor

Rebound/withdrawal
Rebound hypertension via withdrawal on account of tolerance upon the abrupt discontinuation of methyldopa has been reported. Mechanism of action
The mechanism of action of methyldopa is not fully clear.