Quantitative investigations of the epidemiology of phocine distemper virus (PDV) in European common seal populations.

This paper uses simple mathematical models to examine the long-term dynamic consequences of the 1988 epizootic of phocine distemper virus (PDV) infection in Northern European common seal populations. In a preliminary analysis of single outbreaks of infection deterministic compartmental models are used to estimate feasible ranges for the transmission rate of the infection and the level of disease-induced mortality. These results also indicate that the level of transmission in 1988 was probably sufficient to eradicate the infection throughout the Northern European common seal populations by the end of the first outbreak. An analysis of longer-term infection dynamics, which takes account of the density-dependent recovery of seal population levels, corroborates this finding. It also indicates that a reintroduction of the virus would be unlikely to cause an outbreak on the scale of the 1988 epizootic until the seal population had recovered for at least 10 years. The general ecological implications of these results are discussed.

A five-year follow-up study of bone mass in older people.

Bone mass was estimated in a simple random sample of older people from Edinburgh (215 men and 272 women aged 62-90 years), by measuring metacarpal cortical thickness and by measuring the optical density of the radius compared with that of a metal wedge on an X-ray. Information was also collected about diet, energy expenditure and anthropometric variables. The two bone mass estimations were moderately correlated (0-47 in men, 0-53 in women). Both showed decrease as age increased. Estimates of bone mass increased as body size or activity increased, but were unrelated to dietary intakes of calcium or vitamin D. Five years later the cortical thickness was remeasured in 111 men and 141 women. Loss of bone was not uniform, and some subjects actually showed a gain. The mean loss was 0-27 mm (SD 0-41) in men and 0-28 (SD 0-40) in women. This loss was unrelated to body size or to intake of calcium and vitamin D.

A dietary survey of older people in Edinburgh.

1. Dietary histories covering 1 week were obtained from 212 men and 263 women, aged 62--90 years, who formed a random sample of the older people living in a defined area of Edinburgh. The histories were validated by 2 d weighed-diet records for 219 of the subjects. 2. Nutrient intakes are given as mean values and standard deviations, and as percentage distributions of intake relative to the recommended intakes of nutrients. Intakes are also related to factors which might affect diet adversely. 3. Mean values obtained suggested that intakes were less than recommended intakes for more nutrients for women than for men, particularly values for energy and vitamin D. Values for percentage distributions indicated that a substantial proportion of all subjects had low intakes of ascorbic acid and vitamin D, that the energy intake of many women was low and that for most nutrients a greater proportion of men than of women had the recommended intake. Factors assocIATED With significant proportions of subjects with less than the recommended intakes were mental illness in women and deafness and severe dyspnoea in men. 4. Possible action to improve the diet of the elderly is discussed.

Leucocyte ascorbic acid levels and vitamin C intake in older people.

Leucocyte ascorbic acid (L.A.A.) levels and vitamin C intake were measured in a random sample of men and women aged 62-94 years. L.A.A. distributions are positively skewed but log normal. L.A.A. mean values show no age difference in men but are significantly lower in older women. The mean value for all women (23.88mug/10(8) cells) is significantly higher than that for all men (18.11 mug/10(8) cells). L.A.A. values are significantly higher in both sexes in the six months July to December. Vitamin C intake distributions are positively skewed but not improved by log transformation. No significant age or sex differences were found except that a significantly greater proportion of men over than of those under 70 years have intakes less than 30 mg daily. Mean intake is significantly higher in men but not in women in the six months April to September, though in both sexes a significantly greater proportion have intakes less than 30 mg daily in October to March compared with April to September. Fifty per cent. of men and 58% of women have intakes less than 30 mg daily, 23.6% of men and 28.1% of women have intakes less than 20 mg daily, and 4.7% of men and 3% of women have intakes less than 10 mg daily. These percentages increase during the winter. A moderate correlation is present between vitamin C intake and L.A.A. level. L.A.A. levels increase in parallel with but lag behind seasonal increases in vitamin C intake.