Impact of positively- versus negatively-worded items on the factor structure of three psychological measures: W-BQ22, W-BQ12 & SF-36

Background: The 22-item Well-being Questionnaire (W-BQ22) (Bradley, 1994) includes Anxiety, Depression, Energy and Positive Well-being subscales. However, the constructs of anxiety and depression could not be easily distinguished from each other. Consequently, the W-BQ12 was designed to include just three subscales, Negative Well-being (including only negatively-worded anxiety and depression items), Energy (2 positively- and 2 negativelyworded items) and Positive Well-being (all positively-worded items). The SF-36 (Ware & Sherbourne, 1983), a widely used health status measure, includes a 4-item vitality subscale (2 positively- and 2 negatively-worded items) and a 5-item mental health scale (2 positively worded and 3 negatively-worded items).

Method: Factor structures of W-BQ22, W-BQ12 and SF-36 were compared using data from 789 outpatients with diabetes.

Results: W-BQ22 factor analysis showed negatively-worded anxiety and depression items loading together, while positively-worded depression items loaded with positive well-being items and separately from positively-worded anxiety items. W-BQ12 loaded as intended on 3 factors, with negatively-worded anxiety and depression items loading together on one factor: negative well-being. The four energy items (2 positively- and 2 negatively-worded) loaded together (factor 3) and the four positive well-being items loaded together (factor 1). Unforced factor analysis of the SF-36 produced 5 factors and split the mental health and vitality items into two components, which could only be defined in terms of positive and negative wording. A forced 8-factor solution produced similar results, with the mental health and vitality items being split into two components according to their positive or negative wording. A forced 2-factor solution brought mental health/vitality items together, separate from physical health items.

Conclusion: The previously unrecognised influence of positive and negative wording on factor structure is clearly shown here to be of importance in conceptualising and designing measures of psychological well-being to be used with people with diabetes and may be of relevance for other populations.

Training in flexible, intensive insulin management to enable dietary freedom in people with type 1 diabetes : dose adjustment for normal eating (DAFNE) randomised controlled trial

Objectives: To evaluate whether a course teaching flexible intensive insulin treatment combining dietary freedom and insulin adjustment can improve both glycaemic control and quality of life in type 1 diabetes.

Design: Randomised design with participants either attending training immediately (immediate DAFNE) or acting as waiting list controls and attending “delayed DAFNE” training 6 months later.
Setting: Secondary care diabetes clinics in three English health districts.

Participants: 169 adults with type 1 diabetes and moderate or poor glycaemic control.

Main outcome measures: Glycated haemoglobin (HbA1c), severe hypoglycaemia, impact of diabetes on quality of life (ADDQoL).

Results: At 6 months, HbA1c was significantly better in immediate DAFNE patients (mean 8.4%) than in delayed DAFNE patients (9.4%) (t=6.1, P<0.0001). The impact of diabetes on dietary freedom was significantly improved in immediate DAFNE patients compared with delayed DAFNE patients (t=−5.4, P<0.0001), as was the impact of diabetes on overall quality of life (t=2.9, P<0.01). General wellbeing and treatment satisfaction were also significantly improved, but severe hypoglycaemia, weight, and lipids remained unchanged. Improvements in “present quality of life” did not reach significance at 6 months but were significant by 1 year.

Conclusion: Skills training promoting dietary freedom improved quality of life and glycaemic control in people with type 1 diabetes without worsening severe hypoglycaemia or cardiovascular risk. This approach has the potential to enable more people to adopt intensive insulin treatment and is worthy of further investigation.

Trophic effects of fishing southern rock lobster Jasus edwardsii shown by combined fatty acid and stable isotope analyses

The southern rock lobster Jasus edwardsii is a commercial species that has benefited from the complete protection offered by no-take reserves, with higher abundances and larger animals recorded in reserves than in adjacent fished areas. What remains unclear is whether there is any change in the diet of lobsters in reserves, for example, as a result of increased intraspecific competition for food. We used combined chemical tracers to examine the diet of lobsters in fished and reserve areas in 2 bioregions in eastern Tasmania. δ15N values of lobsters were richer in fished than in reserve areas, indicating that lobsters eat a greater proportion of food items from higher trophic levels in fished areas. Mixing models suggest that ascidians, sea urchins and the turbinid gastropod were all important food sources for lobsters, but the importance of these food items differed between bioregions. This spatial variability may suggest that the small size of the reserve in one bioregion is inadequate at ensuring the diet of lobsters is protected from fishing pressure. Fatty acid profiles of lobsters supported the importance of these food sources to lobsters. Differences between bioregions, or inside and outside of reserves, were not apparent using fatty acids. The present study highlights that lobster fishing has the capacity to alter the trophic status of prey for generalist predators and suggests that fatty acid analyses may be limited in detecting changes in the dietary composition of such generalist feeders.