Long-Term Physical Activity Patterns and Health-Related Quality of Life in U.S. Women

Background

Despite studies showing that physically active individuals report higher quality-of-life scores, few data exist on the impact of changing physical activity levels on subsequent changes in quality of life.

Methods

Subjects were 63,152 women in the Nurses’ Health Study aged 40 to 67 years in 1986. Women reported their physical activity on questionnaires in 1986, 1988, 1992, 1994, and 1996, and were grouped according to quartile of change in activity from 1986 to 1996. Women also reported seven health-related quality-of-life dimensions in 1996 and 2000 using the Medical Outcomes Study Short-Form 36 Health Status Survey. The main outcome measures were scores for each of these seven dimensions in 1996, as well as changes in each of these dimensions from 1996 to 2000. Data were analyzed in 2006.

Results

In age and baseline activity adjusted analyses, compared to women whose physical activity was relatively stable from 1986 to 1996, women who saw any increase in physical activity levels had higher quality-of-life scores in 1996. Among women with a clear increase in physical activity, the increase in quality-of-life scores ranged from 2.23 (95% confidence intervals [CI]=1.94–2.52) for mental health to 8.23 (95% CI=7.49–8.97) for role limitations due to physical problems. Increasing physical activity also was associated with greater increases in quality-of-life scores from 1996 to 2000 compared to women whose physical activity level was stable. The strongest association was for role limitations due to physical problems, where women with a clear increase in physical activity had a significant improvement (1.81, 95% CI=1.09–2.53) in the outcome.

Conclusions

Long-term physical activity patterns are an important determinant of health-related quality of life.

Introduction

Physical inactivity is associated with increased risk of many adverse health conditions, including obesity, cardiovascular disease, diabetes, and certain cancers.¹ In addition, active individuals often report higher health-related quality-of-life scores, an association that is supported by a conceptual model proposed by Stewart and King.2, 3 Short-term intervention studies have found increases in physical activity to be associated with improved quality of life.4, 5 However, no longitudinal study has investigated the relationship between long-term change in physical activity and subsequent change in health-related quality of life.

Cross-sectional analyses have found that higher levels of physical activity were positively associated with physical functioning, vitality, and mental health in women.6, 7, 8, 9 In other cross-sectional analyses, physically active individuals reported fewer unhealthy days (physical or mental),10, 11, 12 although this finding is not universal.¹³ Cross-sectional research also suggests that physical activity is associated with greater well-being, successful aging, and improved global quality of life,4, 14, 15, 16 although some studies have found no association.17, 18 The equivocal results may be due to differences in research design and the small sample sizes employed in some studies.

Longitudinal research has consistently found that physical activity is associated with better well-being and physical functioning.5, 19, 20, 21, 22 Physical activity has also predicted decreased risk of declining self-rated health,²⁰ improved social functioning,²³ less difficulty with activities of daily living,¹⁹ and successful aging.²⁴ Only one longitudinal study has examined the influence of change in physical activity,²³ but it employed simultaneous assessments of change in physical activity and change in quality of life, which raises the possibility that changes in quality of life preceded change in activity or that underlying conditions caused both changes.

Other research investigating change in physical activity has consisted primarily of short-term exercise intervention studies with mixed results; some find exercise programs improve quality of life, but many find no relationship.2, 4, 5, 25, 26, 27, 28 These equivocal results may be due to varying population demographics and intervention designs, small sample sizes, or study design limitations (such as the post hoc grouping of subjects by intervention adherence or lack of a control group). Furthermore, the changes made in these intervention studies may not reflect sustained change over the long term.

While research has examined the relationship between physical activity and health-related quality of life at single time points, longitudinal research on the impact of changing physical activity, especially over the long term, on quality of life is limited and reverse causation cannot be ruled out. Exercise training programs provide suggestive data about improved quality of life within the short term, but limited data exists on the long-term impact. With only half of adults in the United States meeting recommended physical activity levels and an additional 26% considered inactive,²⁹ it is important to understand the effect that changing physical activity patterns may have on health-related quality of life. Thus, the authors sought to examine the relation between activity and quality of life in a large population of healthy women.