Alison Brodie

The Contributions of Solar Ultraviolet Radiation Exposure and Other Determinants to Serum 25-Hydroxyvitamin D Concentrations in Australian Adults: The AusD Study

The Quantitative Assessment of Solar UV [ultraviolet] Exposure for Vitamin D Synthesis in Australian Adults (AusD) Study aimed to better define the relationship between sun exposure and serum 25-hydroxyvitamin D (25(OH)D) concentration. Cross-sectional data were collected between May 2009 and December 2010 from 1,002 participants aged 18-75 years in 4 Australian sites spanning 24° of latitude. Participants completed the following: 1) questionnaires on sun exposure, dietary vitamin D intake, and vitamin D supplementation; 2) 10 days of personal ultraviolet radiation dosimetry; 3) a sun exposure and physical activity diary; and 4) clinical measurements and blood collection for 25(OH)D determination. Our multiple regression model described 40% of the variance in 25(OH)D concentration; modifiable behavioral factors contributed 52% of the explained variance, and environmental and demographic or constitutional variables contributed 38% and 10%, respectively. The amount of skin exposed was the single strongest contributor to the explained variance (27%), followed by location (20%), season (17%), personal ultraviolet radiation exposure (8%), vitamin D supplementation (7%), body mass index (weight (kg)/height (m)(2)) (4%), and physical activity (4%). Modifiable behavioral factors strongly influence serum 25(OH)D concentrations in Australian adults. In addition, latitude was a strong determinant of the relative contribution of different behavioral factors.

The AusD Study: A Population-based Study of the Determinants of Serum 25-Hydroxyvitamin D Concentration Across a Broad Latitude Range

Observational studies suggest that people with a high serum 25-hydroxyvitamin D (25(OH)D) concentration may have reduced risk of chronic diseases such as osteoporosis, multiple sclerosis, type 1 diabetes, cardiovascular disease, and some cancers. The AusD Study (A Quantitative Assessment of Solar UV Exposure for Vitamin D Synthesis in Australian Adults) was conducted to clarify the relationships between ultraviolet (UV) radiation exposure, dietary intake of vitamin D, and serum 25(OH)D concentration among Australian adults residing in Townsville (19.3°S), Brisbane (27.5°S), Canberra (35.3°S), and Hobart (42.8°S). Participants aged 18-75 years were recruited from the Australian Electoral Roll between 2009 and 2010. Measurements were made of height, weight, waist:hip ratio, skin, hair, and eye color, blood pressure, and grip strength. Participants completed a questionnaire on sun exposure and vitamin D intake, together with 10 days of personal UV dosimetry and an associated sun-exposure and physical-activity diary that was temporally linked to a blood test for measurement of 25(OH)D concentration. Ambient solar UV radiation was also monitored at all study sites. We collected comprehensive, high-quality data from 1,002 participants (459 males, 543 females) assessed simultaneously across a range of latitudes and through all seasons. Here we describe the scientific and methodological issues considered in designing the AusD Study.

The relationship between ambient ultraviolet radiation (UVR) and objectively measured personal UVR exposure dose is modified by season and latitude

Despite the widespread use of ambient ultraviolet radiation (UVR) as a proxy measure of personal exposure to UVR, the relationship between the two is not well-defined. This paper examines the effects of season and latitude on the relationship between ambient UVR and personal UVR exposure. We used data from the AusD Study, a multi-centre cross-sectional study among Australian adults (18-75 years), where personal UVR exposure was objectively measured using polysulphone dosimeters. Data were analysed for 991 participants from 4 Australian cities of different latitude: Townsville (19.3°S), Brisbane (27.5°S), Canberra (35.3°S) and Hobart (42.8°S). Daily personal UVR exposure varied from 0.01 to 21 Standard Erythemal Doses (median = 1.1, IQR: 0.5-2.1), on average accounting for 5% of the total available ambient dose. There was an overall positive correlation between ambient UVR and personal UVR exposure (r = 0.23, p < 0.001). However, the correlations varied according to season and study location: from strong correlations in winter (r = 0.50) and at high latitudes (Hobart, r = 0.50; Canberra, r = 0.39), to null or even slightly negative correlations, in summer (r = 0.01) and at low latitudes (Townsville, r = -0.06; Brisbane, r = -0.16). Multiple regression models showed significant effect modification by season and location. Personal exposure fraction of total available ambient dose was highest in winter (7%) and amongst Hobart participants (7%) and lowest in summer (1%) and in Townsville (4%). These results suggest season and latitude modify the relationship between ambient UVR and personal UVR exposure. Ambient UVR may not be a good indicator for personal exposure dose under some circumstances.

Trends and challenges in intervention research methods

Community interventions offer a promising option for reducing both intentional and unintentional injuries in children and adults as a result of their potential to influence and achieve widespread, long-term change in a large number of individuals from the population(s) at risk. Community interventions can positively influence individuals’ behavior(s) while they facilitate positive and health-enhancing changes to people’s living environments. They can also have a long-term and sustainable influence on societal norms that are relevant to safety and related behaviours (Oldenburg & Burton, 2004). Community-based interventions and public health interventions do not aim to lower the injury or harm risk of single individuals but aim to reduce the average level of risk in a large group of individuals or population subgroup by delivering interventions or programs in settings such as schools, workplaces, and other public settings. Typically, such an approach uses a broad array of strategies that may include educational/behavioural, engineering/technology, and legislation/ enforcement components (Klassen, MacKay, Moher, Walker, & Jones, 2000; Sleet & Gielen, 2004). Educational/behavioural strategies aim to increase the awareness of injury risk and the importance of risk-reducing behaviors and include media broadcasts, public service announcements, classroom instruction, written material, incentives, negative feedback, behavioral change strategies, and modeling (Klassen et al., 2000). The goal of engineering/technology interventions is to alter the physical environment (such as by placing speed humps on streets or installing smoke detectors in homes) or modify the design of safety devices (such as bicycle helmets or child passenger seats). Finally, legislation/enforcement interventions involve the passage and enforcement of new laws or the increased enforcement of existing laws (Klassen et al., 2000). Generally speaking, the particular strategies used differ among the communities in which they are applied due to differences in population characteristics,