Serum vitamin C status of people in New South Wales: retrospective analysis of findings at a public referral hospital

To examine the relationship between vitamin C status and demographic factors in New South Wales on the basis of serum vitamin C test results undertaken at the central pathology laboratory in Sydney, and to assess associations with age, gender, social disadvantage, and geographic remoteness.


Research
Serum vitamin C status of people in New South Wales: retrospective analysis of findings at a public referral hospital Puja Bhattacharyya 1,2 , Kathrin Schemann 3 , San San Min 4,5 , David R Sullivan 4,5 , Stephen J Fuller 1,6 V itamin C plays diverse physiological roles, including in the assembly of mature collagen, reactive oxygen species scavenging, and immune system function. 1Vitamin C deficiency causes symptoms that include poor wound healing and, in cases of severe deficiency, scurvy, a vessel-mediated bleeding disorder.It is critical that scurvy be recognised and treated early, as fatal haemorrhage is possible in advanced disease. 2 Recommended vitamin C intake for adults is 45 mg/day, and 60 mg/day for pregnant women and 85 mg/day for lactating women. 38][9] The prevalence of vitamin C deficiency in the United States, Canada, and Germany in these studies was 3-7%; 4,7,8 it was higher in the United Kingdom (men, 26%; women, 16%), but this study included only people with low incomes. 9These and other investigations 2,4,10 have found that the risk of vitamin C deficiency is higher for men, older people, those who misuse alcohol or smoke, for people with psychiatric or neurodevelopmental disorders, or cancer, or undergoing renal replacement therapy, and for residents of areas of low socio-economic status.
In New South Wales, 13.3% of people live below the poverty line, the proportion in individual suburbs and towns ranging between 4% and 28%. 11In western Sydney, scurvy has been described in people presenting to hospital with bleeding 12 and people with diabetes with lower limb ulcers, 6 and low vitamin C levels have been identified by pre-surgery screening. 13We examined the relationship between serum vitamin C status and demographic factors in NSW by analysing data from the Royal Prince Alfred Hospital, a centralised public referral hospital in Sydney.

Methods
We undertook a retrospective analysis of vitamin C tests undertaken by the central public reference laboratory at the Royal Prince Alfred Hospital (RPAH) during the period 1 January 2017 -31 December 2021.This laboratory is the only NSW Health Pathology laboratory that performs vitamin C testing for inpatients and outpatients at all NSW public hospitals (apart from the Children's Hospital at Westmead); a small number of samples from other Australian states and territories are also tested.The vitamin C level, age, gender, and postcode for each tested person were extracted from the RPAH biochemistry department vitamin C testing database.Postcode-based socioeconomic status was defined according to the Socio-Economic Indexes for Areas (SEIFA) Index of Relative Socio-Economic Advantage and Disadvantage (IRSAD) 14 and postcode-based geographic remoteness according to the Australian Statistical The known: In developed countries, vitamin C deficiency is more frequent among men, older people, people who smoke or are overweight, and those living in areas of lower socio-economic status.
The new: In the largest Australian study of risk factors for low vitamin C levels to date, the population proportion of findings of low vitamin C levels was larger for people from areas of lower socio-economic status or living in regional or remote communities.
The implications: Socio-economic disadvantage increases the risk of vitamin C deficiency, which is a significant public health problem in both developed and developing countries.

Research
Geography Standard (ASGS), edition 3. 15 For people tested more than once during the study period, the test yielding the lowest vitamin C level was included in our analysis.The indication was not recorded for most samples; in Australian studies, the most frequent reasons for testing have been easy bruising or bleeding, non-healing ulcers in people with diabetes, and pre-operative screening. 6,12,13rum vitamin C concentrations had been determined by the RPAH biochemistry department laboratory using hydrophilic interaction chromatography, with a detection limit of 5 μmol/L and the normal range defined as 40-100 μmol/L.

Statistical analysis
The main outcome was vitamin C status: a concentration of 40 μmol/L or more was deemed normal, a value of 12-39 μmol/L to indicate hypovitaminosis C, and a value of less than 12 μmol/L to indicate significant deficiency. 4,6The distribution by five variables -year of testing, age, gender, IRSAD quintile, and remoteness category -was assessed both for all tested people and for the three vitamin C status categories.Data for categorical variables are summarised as numbers and frequencies, for numerical variables as medians with interquartile ranges (IQRs).
Associations between each of the five variables and vitamin C status were initially assessed in univariable ordinal logistic regression models.The parallel regression assumption was assessed with Brant's test; as it provided evidence of violation of the assumption of proportional odds for four of the univariable models (Supporting Information, table 1), univariable and multivariable multinomial models were fitted to vitamin C status.All five variables were considered in multivariable multinomial model building using the multinom function in the R package nnet, 16 using manual backward elimination.Two-way interaction terms between year and each of the other variables were sequentially added to the multivariable main effects model for testing to derive the final model; variables for which P < 0.05 were included in the final model.Two ordinary binary logistic models were fitted, and testing to identify outliers and influential data points undertaken.We report odds ratios (ORs) and adjusted ORs (aORs) with 95% confidence intervals (CIs).
We mapped the estimated rate of vitamin C test findings of hypovitaminosis C or significant deficiency (per 100 000 estimated resident population) by Statistical Area 3 (SA3) for Greater Sydney and for regional NSW by linking postcodes to SA3 geography and estimated resident population by SA3. 17 All data management and statistical analyses were conducted in R 4.3.0(R Core Team) using R Studio 2023.03.1 + 446 (Posit) and the tidyverse package suite. 18For mapping, a Statistical Areas 3 (SA3) boundary shapefile 2021 (Environmental Systems

Discussion
The distribution of prosperity and socio-economic disadvantage in NSW is uneven in both urban and regional areas. 11isadvantage influences diet, including the consumption of fresh fruit and vegetables, and thereby the risk of vitamin C deficiency. 21Several cohort and case studies of vitamin C deficiency in western Sydney have been reported 6,12,13 but no large studies of vitamin C status across NSW.
To determine the demographic factors associated with vitamin C status in NSW, we analysed a large dataset of vitamin C tests undertaken at a central public reference laboratory.
In our univariable multinomial analyses, the likelihood of hypovitaminosis C and significant deficiency relative to findings of normal vitamin C levels increased with age, level of local disadvantage, and geographic remoteness; men were more likely to have a significant deficiency than women, but not hypovitaminosis C. In the multivariable model, the likelihood of vitamin C deficiency relative to findings of normal vitamin C levels increased with socio-economic disadvantage, and was higher for men; remoteness itself did not significantly influence the odds of deficiency, mainly because its effects overlapped with those of other factors (eg, remoteness).The number of people with significant deficiency declined each year until 2020; but in 2021, the probability of people under 75 years of age having a significant deficiency was higher than in 2019 and 2020.The reason for this rise, and for an even larger rise in the probability of hypovitaminosis C, may be related to changes in diet during COVID-19 lockdowns, including altered consumption of fresh fruit and vegetables during this period; 22  Research in general practice have been reported. 23Increased vitamin C testing may be related to rising concern about dietary adequacy or, as for vitamins D and B 12 testing, could reflect differences between patients and doctors regarding appropriate indications for testing. 23Alternatively, the increased number of tests may reflect population growth; the NSW population grew between 2017 and early 2020 before stagnating in 2020 and 2021 during the COVID-19 pandemic. 24though the number of vitamin C tests increased each year, the deficiency rate did not decline after 2018.This suggests that awareness among clinicians of the importance of vitamin C has grown, but also that some people with symptoms of deficiency do not undergo assessment or are unaware of the risk of deficiency, and that not all clinicians order tests when indicated.We do not know whether dietary intake of vitamin C is declining, but consumption of fruit and vegetables in NSW did not change during the study period; 25 the proportion of NSW adults who were overweight or obese, however, increased. 26e estimated rates of hypovitaminosis C or significant deficiency test results by resident population were highest in Liverpool (in southwestern Sydney).Several of the areas with the highest low vitamin C rates were areas of greatest of disadvantage in NSW, including the Bringelly-Green Valley SA3 (poverty rate, 27.7%) and Tamworth West (24.6%). 11Higher rates may also reflect the local food environment; for example, in the Penrith local government area (in the Penrith SA3), there are as many as seventeen unhealthy food outlets for each healthy outlet. 27

Limitations
Selection bias limits the external validity of our study and consequently the generalisability of our findings. 28Our study sample was not derived by random selection, and may not be representative of the general NSW population with respect to the prevalence of hypovitaminosis and significant vitamin C deficiency. 28Further, the reasons for assessing vitamin C levels were not available to us and the population from which our sample was drawn could not be clearly defined.

Conclusion
We found that vitamin C deficiency, particularly among people living in areas of lower socio-economic status and remote communities, may be more frequent in NSW than generally recognised.Vitamin C levels below 11.4 μmol/L are associated with clinical scurvy; the consequences of hypovitaminosis C have not been established, but symptoms can include fatigue, impaired immune responses and wound healing, and cardiovascular disease. 1 Strategies for increasing the consumption of foods rich in vitamin C include education, national dietary guidelines, 21 and making fresh fruit and vegetables more affordable.As people living in areas of lower socio-economic status consume less healthy food and drink than those in higher status areas, 21 increasing their household income could increase vitamin C intake; the economic stimulus measures of the Australian government during the COVID-19 pandemic led to welfare-dependent people eating healthier food more regularly. 29A more comprehensive investigation of the prevalence of vitamin C deficiency could identify groups for whom ensuring the recommended daily intake of vitamin C might be an inexpensive and effective public health intervention.
however, most relevant studies did not take socio-economic factors into account.The number of vitamin C tests undertaken increased each year of the study period.Increasing numbers of other vitamin tests 4 Serum vitamin C tests undertaken for 12 793 people at the Royal Prince Alfred Hospital, 2017-2021: effects plot for the year-age interaction term in the multivariable multinomial model

1 Characteristics of 12 934 people whose serum vitamin C levels were assessed at the Royal Prince Alfred Hospital, 2017-2021, overall and by vitamin C status Vitamin C status
16searchResearch Institute) was downloaded from the Australian Bureau of Statistics19and processed with the R package sf 1.0-14.20Multinomialregressionanalyses used the R package mass 7.3-60.16 IRSAD = Index of Relative Socio-economic Advantage and Disadvantage.* Not available for nine tested people.◆ 2 Age

distribution of 12 934 people whose serum vitamin C levels were assessed at the Royal Prince Alfred Hospital, 2017-2021, overall and by vitamin C status* The
data for this figure, and the mean serum vitamin C values, are included in the Supporting Information, table 2; a violin plot of the age distribution is included in the Supporting Information, figure 1. ◆

Geographic distribution in regional and metropolitan NSW of hypovitaminosis C and significant deficiency test results during 2017-2021 In
Coffs Harbour, the rate of test results indicating hypovitaminosis C or significant deficiency was 82.1 per 100 000 residents, in Lithgow-Mudgee 58.6 per 100 000 residents, and in Tamworth-Gunnedah 48.3 per 100 000 residents; the rates in Lower Murray, Gosford, Clarence Valley, and Maitland were between 31.3 and 37.3 per 100 000 residents.In Greater Sydney, the rate was 113.2 per 100 000 residents in Liverpool, 72.8 per 100 000 in Parramatta, 64.5 per 100 000 in Camden, 55.1 per 100 000 in Bringelly-Green Valley, 53.5 per 100 000 in St Marys, 52.9 per 100 000 in Mount Druitt, 35.9 per 100 000 in Blacktown and 34.5 per 100 000 in Richmond-Windsor (Box 6).

5 Serum vitamin C tests undertaken for 12 793 people at the Royal Prince Alfred Hospital, 2017-2021: multivariable multinomial analysis* Adjusted odds ratio (95% CI)
= confidence interval; IRSAD = Index of Relative Socio-economic Advantage and Disadvantage.* The corresponding results for the interactions of year with gender and postcode-level socio-economic status are included in the Supporting Information, tables 3 and 4. ◆ CI