Longitudinal changes in serum 25-hydroxyvitamin D in older people

Area of Science:

• Gerontology
• Nutritional Science
• Biochemistry

Background:

• Cross-sectional studies suggest a decline in serum 25-hydroxyvitamin D (25OHD) with aging.
• Understanding the factors influencing 25OHD levels over time is crucial for public health.

Purpose of the Study:

• To investigate the longitudinal changes in serum 25OHD levels in an aging population.
• To determine whether age or other factors, such as sun exposure and vitamin D intake, are responsible for observed declines in 25OHD.

Main Methods:

• A longitudinal study design was employed, analyzing serum samples from 136 participants (37 men, 99 women) collected between 1980-1982 and 1989-1994.
• Data collected included age, gender, sample collection date, physical activity, and vitamin D intake via questionnaires.
• Seasonal variations and changes in 25OHD levels were analyzed over an average of 11.4 years, comparing supplemented and unsupplemented groups.

Main Results:

• A seasonal variation in serum 25OHD was observed.
• In individuals not receiving vitamin D supplementation, both serum 25OHD and physical activity decreased significantly over time.
• Serum 25OHD levels did not change in supplemented individuals or during summer months, but declined in winter-to-winter and spring-to-spring comparisons.
• Month, activity level, vitamin D supplementation, and gender were identified as independent determinants of serum 25OHD.

Conclusions:

• The age-related reduction in serum 25OHD is primarily attributed to decreased sun exposure rather than the aging process itself.
• Vitamin D supplementation is effective in preventing the decline of serum 25OHD levels associated with aging.
• Maintaining adequate vitamin D levels may be crucial for health in older adults, especially during seasons with limited sun exposure.