Leisure-time physical activity and circulating 25-hydroxyvitamin D levels in cancer survivors: a cross-sectional analysis using data from the US National Health and Nutrition Examination Survey

BMJ Open. 2017 Jul 10;7(7):e016064. doi: 10.1136/bmjopen-2017-016064.

Abstract

Objectives: Circulating 25-hydroxyvitamin D (25-OHD) is associated with improved cancer prognosis in some studies, yet it may be a surrogate marker for physical activity. We investigated the associations of leisure-time physical activity (LTPA) with circulating 25-OHD levels in cancer survivors, and determined whether associations differ by indoor and outdoor activity.

Design: Cross-sectional study.

Setting: The US National Health and Nutrition Examination Survey (NHANES).

Participants: Cancer survivors with available data on demographic information, measures of adiposity, smoking history, self-reported LTPA and circulating 25-OHD levels in five waves of NHANES (2001-2010).

Main outcomes measures: Circulating 25-OHD levels.

Results: Multivariable linear regression and logistic regression models were used to evaluate the associations of self-reported LTPA with 25-OHD, adjusting for potential confounders. Due to the differences in LTPA measure, the analyses were conducted separately for 2001-2006 and 2007-2010 data. We further estimated associations by indoor and outdoor activity in the 2001-2006 data. There were 1530 cancer survivors (mean age=60.5 years, mean body mass index=28.6 kg/m2). The prevalent cancer sites were breast (19.3%), prostate (18.8%), cervix (10.4%) and colon (8.6%). Compared with inactive cancer survivors, being physically active was associated with higher circulating 25-OHD levels (8.07 nmol/L, 95% CI 4.63 to 11.52) for 2001-2006 data. In the mutually adjusted model, higher outdoor activity (5.83 nmol/L, 95% CI 1.64 to 10.01), but not indoor activity (2.93 nmol/L, 95% CI -1.80 to 7.66), was associated with statistically significantly higher 25-OHD levels. The interaction between indoor and outdoor activities was, however, not significant (p=0.29). The only statistically significant association seen in the 2007-2010 data was among obese cancer survivors.

Conclusion: Physical activity, particularly outdoor activity, is associated with higher 25-OHD levels in cancer survivors. In view of the possible beneficial effects of vitamin D on cancer prognosis, engaging in outdoor physical activity could provide clinically meaningful increases in 25-OHD levels among cancer survivors.

Keywords: NHANES; cancer prognosis; cancer survivor; physical activity; vitamin D.

MeSH terms

  • Body Mass Index
  • Cancer Survivors*
  • Cross-Sectional Studies
  • Exercise*
  • Female
  • Humans
  • Leisure Activities*
  • Linear Models
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Neoplasms / blood*
  • Neoplasms / epidemiology
  • Nutrition Surveys
  • Obesity / epidemiology
  • Prevalence
  • United States / epidemiology
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood

Substances

  • Vitamin D
  • 25-hydroxyvitamin D