Emerging evidence suggest Parkinson’s disease (PD) begins with a decline in functioning years before the disease is diagnosed from conventional symptoms, say Harvard School of Public Health researchers.
Researchers say the new study is the first to examine patterns in the quality of life of Parkinson’ disease patients prior to diagnosis.
Investigators discovered declines in physical and mental health, pain, and emotional health present several years before the onset of the disease and continue thereafter.
“We observed a decline in physical function in PD patients relative to their healthy counterparts beginning three years prior to diagnosis in men and seven and a half years prior to diagnosis in women,” said lead investigator Natalia Palacios, Ph.D., Department of Nutrition, Harvard School of Public Health.
“The decline continues at a rate that is five to seven times faster than the average yearly decline caused by normal aging in individuals without the disease.”
The results are reported in the latest issue of the Journal of Parkinson’s Disease.
Researchers studied 51,350 male health professionals enrolled in the Health Professionals Follow Up Study (HPFS) and 121,701 female registered nurses enrolled in the Nurses’ Health Study (NHS).
In both ongoing studies, participants fill out biannual questionnaires about a variety of lifestyle characteristics and document the occurrence of major chronic disease.
Initiated in 1976, the NHS study is among the largest and longest-running investigations of factors that influence women’s health.
In this study, investigators seek to determine participants health-related quality of life by assessing eight areas: physical functioning, role limitations due to physical problems, role limitations due to emotional problems, vitality, bodily pain, social functioning, mental health, and general health perceptions.
The 1986 HPFS was designed to complement the NHS and measure men’s health and assesses diet and physical activity.
In the current investigation, researchers identified 454 men and 414 women with PD in the two cohorts.
From a review of the data, scientists discovered physical function begins to decline around 7.5 years prior diagnosis of PD. Specifically, a decline began approximately 3 years prior to diagnosis in men and approximately 7.5 years prior to diagnosis in women.
Researchers discovered physical functioning continued to decline thereafter at a rate of 1.43 and 2.35 points per year in men and women, respectively.
In comparison, the average yearly decline in individuals without PD was 0.23 in men and 0.42 in women. Other measures of quality of life, available only in women, declined in a similar pattern.
A strength of the study is the ability to compare individuals before and after their diagnosis with PD with comparison groups. This methodology helped researchers chart the deterioration in functioning and quality of life over the whole study follow-up, which included many years prior to diagnosis.
“This result provides support to the notion that the pathological process leading to PD may start several years before PD diagnosis,” said Palacios. “Our hope is that, with future research, biological markers of the disease process may be recognizable in this preclinical phase.”
Source: IOS Press