Retirement is a major life transition. Retirement may result in a substantial reduction in mental and physical fatigue and depressive symptoms, but retirement does not change the risk of major chronic illnesses such as respiratory disease, diabetes and heart disease.
If work is tiring for many older workers, the decrease in fatigue could simply reflect the removal of the source of the problem. Further, retirement may allow people more time to engage in stimulating and restorative activities, such as physical exercise.
Therefore if fatigue is the primary concern, then the person under consideration may prefer retiring early and certainly he/she will be relieved from mental and physical fatigue, however, it will not solve/change the risk any other chronic diseases. Further, it is really difficult to make definite claims about positive and negative benefits from retirement at a particular age.
I see that older people without a clear goal in life, like work or other duties, a useful hobby are weaker and often die earlier. I think a modest activity, a decent amount of obligations - but in first line, the feeling to be useful and required - prolong life.
I think it depends if the person retiring has a good retirement plan or have enough savings to live a good life. If you retire and does not have money to support even just yourself, it will be very stressful.
Those who have enough savings or good amount of pension can have a more relaxed life on their retirement days. Their health may improved or become better just enjoying their days.