Population-based cross-sectional studies

Cohen O, Vinker S, Yaphe J, Kitai E (2005) Hormone replacement therapy and WONCA/COOP functional status a cross-sectional population-based study of women in Israel. Climacteric 8 171-176... 

The biomarker is validated in a cross-sectional population-based study to determine if there are correlations between self-reported HCA exposure (for example, food frequency questionnaire using photographs similar to the case-control study reported by Butler et al.) and HCA measurements. 

A more explicit weakness of the cross-sectional population-based studies... 

Table 6.1 Cross-sectional, population studies based on dietary intake of soy products and bone mineral density (BMD) or biomarkers of bone turnover...

In reviewing this topic it is clear that most relevant studies are observational population-based studies. These studies are mainly cross-sectional and therefore they are most suitable for generating hypotheses. Some studies are hypothesis-testing clinical experiments, and there are few randomised-controlled trials or meta-analyses. Strong evidence-based recommendations for the prevention of asthma and allergy are unable to be made except for ETS. 

First of all, data on prevalence of ICD and ACD are missing and the few published population-based studies are difficult to compare due to the lack of standardization of case definitions and methods. To be able to compare cross-sectional studies, it is important that some form of standardization is reached about definition of contact dermatitis in epidemiological studies, as well as methods of case ascertainment. 

In the Massachusetts Women s Health Study, a population-based cross-sectional investigation of women, Hernandiz-Avila and colleagues16 also found an inverse linear association with caffeine intake (estimated from... 

Radhika and others (2008) examined the relationship between fruit and vegetable intake (g/day) and CVD risk factors in urban south Indians. The study population composed of 983 individuals aged at least 20 years selected from the Chennai Urban Rural Epidemiological Study (CURES), a population-based cross-sectional study... 

Platts-Mills T, Vaughan J, Squillace S, Woodfolk J, Sporik R Sensitisation, asthma, and a modified Th2 response in children exposed to cat allergen a population-based cross-sectional study. Lancet 2001 357 752-756. 

Bove FJ, Fulcomer MC, Klotz JB, et al. 1992a. Population-based surveillance and etiological research of adverse reproductive outcomes and toxic wastes. Report on Phase IV-A Public drinking water contamination and birthweight, fetal deaths, and birth defects. A cross-sectional study. New Jersey Department of Health. 

In a population-based cross-sectional study of vision and common eye diseases in 3654 people, 49-97 years of age, inhaled glucocorticoid use was reported by 370 subjects, of whom 164 reported current use and 206 previous use. Subjects who reported using inhaled glucocorticoids had a higher prevalence of nuclear cataracts (OR = 1.5 Cl = 1.2, 1.9) and posterior subcapsular cataracts (OR = 1.9 Cl = 1.3, 2.8). The highest prevalence (27%) was in patients whose lifetime dose was more than 2000 mg (relative prevalence 5.5) (SEDA-22,187). 

Laatikainen AK, Kroger HP, Tukiainen HO, Honkanen RJ, Saarikoski SV. Bone mineral density in perimenopausal women with asthma a population-based cross-sectional study. Am J Respir Crit Care Med 1999 159(4 Pt l) 1179-85. 

Cross-Sectional Surveys. These are observational studies in which subjects are contacted at a fixed point in time without regard to either exposure or outcome. The exposure(s) and outcome(s) are then measured in the subjects, and the subjects are assigned to categories based on that information. Cases are a prevalent series of individuals with the disease or outcome, and controls are the remaining population. Cross-sectional studies often deal with exposures that cannot change, such as blood... 

Paunio M, Heinonen OP, Virtanen M, et al Measles history and atopic diseases A population-based cross-sectional study. JAMA 2000 283 343-346. 

Single molecule studies. All the techniques discussed so far provide knowledge about the behaviour of nanocrystals at an ensemble level. Unlike molecules that are identical to each other, several key parameters such as surface chemistry can vary from nanocrystal to nanocrystal. This makes it essential to supplement ensemble information with other types of spectroscopic tools that can convey information regarding speciflc members. Due to the relatively small absorption cross sections of individual members, fluorescence based optical techniques have been frequently used to probe individual members or populations. 

The dynamics of populations of the electronic states in a 4,4 -bis(dimethylamino) stilbene molecule (two-photon absorption) was studied against the frequency, intensity, and shape of the laser pulse [52]. Complete breakdown of the standard rotating wave for a two-photon absorption process was observed. An analytical solution for the interaction of a pulse with a three-level system beyond the rotating wave approximation was obtained in close agreement with the strict numerical solution of the amplitude equations. Calculations showed the strong role of the anisotropy of photoexcitation in the coherent control of populations that can affect the anisotropy of photobleaching. The two-photon absorption cross section of an ethanol solution of a trans-stilbene and its derivatives exposed to radiation of the second harmonic of a Nd YAG laser (532 nm) of nanosecond duration has been detected [53]. In experiments, the method based on the measurement of the photochemical decomposition of examined molecules was used. The quantum yield of the photoreaction (y266) of dyes under one-photon excitation (fourth harmonic Nd YAG laser 266 nm) was detected by absorption method. 

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