Psychosocial stress is a well-established risk factor for many chronic diseases, and previous research has suggested that many psychosocial stressors, such as increased major life events, lower levels of optimism, life satisfaction and education, and may be associated with fractures.
Psychosocial stress refers to the emotional and physiological reactions experienced when an individual confronts a situation in which the demands go beyond their coping resources. Other examples of stressful situations include marital problems, death of a loved one, abuse, health problems, and financial crises.
The premise of this work was that psychosocial stress may increase fracture risk through degradation of bone mineral density (BMD). The authors suggest that psychosocial stress may alter BMD through changes in hormone levels, including cortisol, thyroid hormones, growth hormone and glucocorticoids.
However, few studies have examined the association between psychosocial stress and BMD, so the researchers set out to do this.
They evaluated data on 11,020 postmenopausal women enrolled in the Women's Health Initiative (WHI) - a long term US health study launched in 1993 to assess strategies for preventing heart disease, breast and colorectal cancer, and osteoporotic fractures in postmenopausal women.
The women were part of a substudy looking at bone density, so data on bone density had been collected at enrolment and at a follow-up visit six years later.
The women completed a questionnaire at enrolment which included information about psychosocial stress related to their social environment, specifically on the social strain, social support and social functioning.
Social strain measures negative social interactions and relationships, social support measures positive relationships, and social functioning measures limitations in social activity.
The relationship between these three measures of psychosocial stress and percentage change in BMD over six years were examined.
High social stress was found to be associated with lower BMD over 6 years, after adjusting for potential influencing factors, including age, education, existing conditions, weight (BMI), smoking status, alcohol use, hormone therapy use, age at menopause, physical activity and history of fracture after age 55.
The authors say: "We identified specific psychosocial stressors pertaining to the social environment that was associated with bone loss."
The higher social strain was associated with greater BMD loss of the total hip, lumbar spine (lower back) and femoral neck (just below the ball of the ball-and-socket hip joint) over six years of follow-up. Social functioning stress was associated with greater bone loss at the total hip and femoral neck.
The social strain scores given by the women ranged from 4 to 20 with higher scores indicating more strain, and each point higher was associated with 0.082% greater loss of femoral neck BMD, 0.108% greater loss of total hip BMD and 0.069% greater loss of lumbar spine BMD.
This is an observational study, and as such, can't establish cause, and the authors point out that psychosocial stress levels may have been lower than average because participants in the Women's Health Initiative were healthy individuals living in the community. What's more, psychosocial stress levels were self-reported at the start of the study and may have changed over the follow-up period.
Nevertheless, they say: "We found that bone loss is among the physiological stress responses more strongly related to the quality of social relationships than quantity."
Taken together with prior evidence, "the results support community-building social stress interventions in postmenopausal women to potentially limit bone loss," they conclude.